Electronic Parts and Schematic Diagram

LM3900 Audio Mixer

2011-12-03T14:19:00.002+07:00

This audio mixer circuit doesn’t use a low impedance input to mix no ideal sources, but use many amplifiers to provide ideal sources before mixed through simple resistors. Ideal source means a sources with low impedances, make the interaction between signals in the output doesn’t affect the input. Please note that this mixer circuit has high impedance output, so you’ll need an next processing equipment with appropriate input specs. This audio mixer circuit is designed around an LM3900 quad op amp and combines 2 line and 2 mike inputs and sums them at the output terminal. To vary the gain (around +23 dB), we can change the R7 through R10.

3W BTL Mono Audio Power Amplifier

2011-12-03T14:14:00.003+07:00

For mono output amplifier application, TDA7056 IC can be your option. Compact but powerful, this integrated circuit is contained in a 9 pin medium power package. This device is designed for battery fed portable equipments such as mono recorders, radios and television. To attract the market, TDA7056 has many features such as low power consumption. For more reliable operation, TDA7056 also has short circuit proof and ESD (Electro Static Discharge) protected on all pins. Designing application with this IC should be easy since no external components is needed. To make sure you’ll love this chip, this device also has no switch on/off clicks. Overall, TDA7056 has good stability.

Compressor Circuit with 570/571 Compandor IC

2011-12-03T14:07:00.002+07:00

Compressor circuit provide high gain for low amplitude input and provide low gain for high amplitude input. This action, in effect, produce a nearly constant amplitude even though the input has very high dynamic range (very high amplitude variation from time to time). The action of compression like this is needed in some situation, such as in maximizing modulation depth in broadcasting, or sustaining electric guitar signal which has very high variation between the plucking time and fading out. The following circuit has complementary input/output characteristic and unity gain at 0.775 VRMS input. Voltage gain through compressor is square root of 0.7/Vin. Vin is average input voltage. This circuit uses Signetics dual channel compandor IC. 570 has lower inherent distortion and higher supply voltage range (6-24 V) than 571 (6-18 V).

Sound Activated Lamp.

2011-12-03T13:53:00.003+07:00

This simple circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (sound-controlled) disco light or car’s LED light show. The Q1 amplify the audio from mic. The R1 is used to adjust the peak of signal to greater than about 0.7 volts, act as sensitivity adjuster. A certain level, the signal coming from microphone, after amplification by Q1, will trigger the SCR and light lamp I1. If we change the lamp with a relay, then we can get a sound-activated relay/switch, which can be used to control more powerful / high wattage high voltage lamps. If we use a relay, place a 1N4007 diode in parallel with the relay coil to prevent the back-emf from relay coil destroying the SCR.

List Component :

R1 >> 1K

R2 >> 4.7K

R3 >> 1K

VR1 >> 5K

C1 >> 0.47 mf/16V

Q1 >> HEP802

SCR >> C103

170W Audio Power Amplifier.

2010-09-02T18:25:00.004+07:00

Download this schematic diagram.

Download part list component.

Datasheet semiconductor component.

1. NE5534

2. MJE350

3. MJE340

4. BD139

5. BC546B

6. BC556B

7. MJE15030

8. MJE15031

9. MJE15003

10. MJE15004

11. BAT85

12. IN4004

13. BY254

The circuit is being powered by two 15V power supply for each channel, that is regulated by the combination of resistors R7-9 and Zener diodes D1-2. The frequency bandwidth is limited to a specific value due to the presence of low pass filter from R2 & C2 and high pass filter from R3 & C1. The total feedback of the circuit is concentrated on the positive non-inverting input of the IC1 that functions as differential amplifier. The node of R4-5 is applied with the feedback voltage from the output through R6. The current regulated by R10 & R14 across Q1-2 is 10mA as they operate in class A while in class AB, the power transistors Q8-11 operate in the output with a regulated constant current of 100mA each power transistor, done by trimmer TR1 and Q3. This will match the voltage drop at 27mV, higher than the provided voltage of R25-28.

A heatsink with sufficient dimension to provide cooling is placed above Q1-2-3-6-7 to maintain the possible thermic stability while the protection from reverse voltages from the load is performed by diodes D9-10.Additional fan can also be employed to suppress high temperature for efficient operation. The stability during high frequencies is sustained by the Zobel network consisting of R29 & C18. Due to capacitive load, the amplifier output is protected by a 1mm diameter 15-coil inductor L1 with R30 for square pulses passage.

Each power amplifier that is created will correspond to a transformer to handle large capacitors and provide proportional power. The transformer input is connected to the AC line which can incorporate delay circuit for protection from excessive supply. The cables that would carry the current to the amplifier should be appropriate enough.

1000 W Power Amplifier Schematic Diagram.

2010-09-01T12:00:00.004+07:00

Download this schematic diagram.

Datasheet semiconductor component download.

1. BC546
2. BD681
3. MJE350
4. MJE340
5. 2SC5200
6. 2SA1943
7. 2SA1494
8. 2SC3858

The assemble cables for DC power supply and output transistors must be large, use size 1.5-3mm for large current passed. The supply used transformer with 20A/45Ct and at least 4x10000uf/80 volt capasitor. this circuit is able to supply power 10000watt therefore the power transistor will be very hot, give good cooling fan on the power transisitor

Transitor alternative to replacement of the 2SA1494 is 2SA1216 From SANKEN. The transistor has a 200-350 watt power dissipation of each pair so that for long-term operation of more durable. Keep in mind, usually sold a pair of power transistors with its complement, so you can not buy 2SC2922 alone without 2SA1216 or 2SA1494 without 2SC3858.

200W ATX PC Power Supply Electronic Circuit.

2010-09-01T07:00:00.007+07:00

Download this schematic diagram.

Datasheet semiconductor component. (PDF Format)

1. IN5406
2. 2SC4242
3. FR155
4. 2SC945
5. 2SA733
6. 2SC3457
7. LM7805
8. TL494
9. LM393
10. TL431C

Here I bring you wiring diagram of PCs power supply of DTK company. This power supply has ATX design and 200W performance. I was drawed diagram, when I repaired this power supply.

This power supply circuit uses chip TL494. Similar circuit is used in the most power supplies with output power about 200W.Device use push-pull transistor circuit with regulation of output voltage.

Line voltage goes through input filter circuit (C1, R1, T1, C4, T5) to the bridge rectifier. When voltage is switched from 230V to 115V, then rectifier works like a doubler. Varistors Z1 and Z2 have overvoltage protect function on the line input.
Thermistor NTCR1 limits input current until capacitors C5 and C6 are charged. R2 and R3 are only for discharge capacitors after disconnecting power supply. When power supply is connected to the line voltage, then at first are charged capacitors C5 and C6 together for about 300V.
Then take a run secondary power supply controlled by transistor Q12 and on his output will be voltage. Behind the voltage regulator IC3 will be voltage 5V, which goes in to the motherboard and it is necessary for turn-on logic and for "Wake on something" functions.
Next unstabilized voltage goes through diode D30 to the main control chip IC1 and control transistors Q3 and Q4. When main power supply is running, then this voltage goes from +12V output through diode D.

95 Watt Laptop Power Supply For Car.

2010-08-31T17:59:00.004+07:00

Download this schematic diagram.

Download part list component.

Datasheet semiconductor component: (PDF Format)

1. MBR1645
2. IRL2505
3. BD139
4. BD140
5. UC3843N

A laptop or anthology computer user while they are abroad from the home or appointment knows that eventually or after they will charge to bung into a mains aperture to top up the batteries. The car cigarette lighter atrium in the car is additionally an electrical aperture but it can alone accumulation 12 V. That’s no botheration for the Laptop Ability Accumulation declared here. The laptop ability accumulation declared actuality plugs into a car cigarette lighter atrium and produces a 19V nominal achievement voltage adjustable by + – 0.5V. The ascribe voltage ambit is from 9.2V to 15V and the achievement voltage shows acceptable adjustment alike with ample fluctuations of the ascribe voltage. The achievement can accumulation 5A continuosly with abrupt excursions up to 10A.

The ability semiconductor heatsinks of this laptop ability accumulation are dimensioned fo 5A connected so continued operation up to 10A will access amusement in the adapter and in acute cases will account the ascribe agglutinate to complain.

20VAC 60 Watt Sunrise Lamp Circuit.

2010-08-31T17:43:00.004+07:00

Download this schematic diagram.

Datasheet semiconductor component.

1. LM324
2. IRF640
3. IRF740

In this circuit, a 120VAC lamp is slowly illuminated over a approximate 20 minute period. The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp. A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power. The bridge rectifier should be rated at 200 volts and 5 amps or more. In operation, a 700 Hz triangle waveform is generated at pin 1 of the LM324 and a slow rising voltage is obtained at pin 8. These two signals are compared at pins 12 and 13 to produce a varying duty cycle rectangular waveform at pin 14, which controls the MOSFET and brightness of the 60 watt lamp. When power is applied, the lamp will start to illuminate within a minute or so, and will slowly brighten to full intensity in about 20 minutes. You can make that longer or shorter with adjustments to the 270K resistor at pin 9. The 2.2 ohm resistor and .015uF cap connected to the lamp serve to supress RFI. The diode at pin 9 and 10K resistor on pin 8 are used to discharge the 3300uF cap when power is removed. Power should be off for a few minutes before re-starting.

Caution: This circuit is connected directly to the AC line and presents a hazard if any part is touched while connected to the line. Use caution and do not touch any parts while the circuit is connected to the AC line. You may want to use a 9 volt battery connected across the 12 volt zener to check the basic operation. The DC voltage at pins 1,2,3,5,6,7 will all be around 4.3 volts if the circuit is working correctly. If the DC voltages are all correct, you can use a variac to slowly apply the full line voltage and check for proper operation.

88-108 MHz FM Broadcast Transmitter Circuit.

2010-08-31T17:32:00.003+07:00

Download this schematic diagram.

Datasheet semiconductor component.

1. NE555
2. 2N4392

This circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be
received to about 100 yards. A 555 timer is used to produce the tone (about 600 Hz) which frequency modulates a Hartley oscillator. A second JFET transistor buffer stage is used to isolate the oscillator from the antenna so that the antenna position and length has less effect on the frequency. Fine frequency adjustment can be made by adjusting the 200 ohm resistor in series with the battery. Oscillator frequency is set by a 5 turn tapped inductor and 13 pF capacitor. The inductor was wound around a #8 X 32 bolt (about 3/16 diameter) and then removed by unscrewing the bolt. The inductor was then streached to about a 3/8 inch length and tapped near the center. The oscillator frequency should come out somewhere near the center of the band (98 MHz) and can be shifted higher or lower by slightly expanding or compressing the inductor. A small signal diode (1N914 or 1N4148) is used as a varactor diode so that the total capacity in parallel with the inductor varies slightly at the audio rate thus causing the oscillator frequency to change at the audio rate (600 Hz). The ramping waveform at pins 2 and 6 of the timer is applied to the reversed biased diode through a large (1 Meg) resistor so that the capacitance of the diode changes as the ramping voltage changes thus altering the frequency of the tank circuit. Alternately, an audio signal could be applied to the 1 Meg resistor to modulate the oscillator but it may require an additional pullup resistor to reverse bias the diode. The N channel JFET transistors used should be high frequency VHF or UHF types (Radio Shack #276-2062 MPF102) or similar.

40 Watt Fluorescent Lamp Schematic Diagram.

2010-08-31T16:23:00.003+07:00

Download this schematic diagram.

Download part list component.

The circuit works much like the original Strobos. except that a fluorescent tube is used. Thus, the fluorescent tube zündbereit remains constant, the two electrodes of the tube are continuously transformer Ta1 supplied with electricity. This current makes the two resistance wires of the glow tube in, so the mercury evaporates into the tube and the electron emission is simplified. Ta2 Returns on the rectifier “D1-D4 , the voltage of the multivibrator, the ignition frequency of the tube is responsible for. The speed of the AMV is with potentiometer P1 set. The pulse then passes through R3 to T3, is amplified there and controls the bias for the triac, the conducting of these alternates. If so, then the circuit through the tube and the ballast closes and the tube can light up. The pulses of T3 also enter via the capacitor C3 to the gate of the thyristor Th1. Simultaneously with the closing “of the circuit for the tube is Th1 -conductive and creates a short in the ignition coil current flow, which in turn generates a high voltage on the secondary. This voltage of several thousand volts is now operational on port J7 to a wire outside of the tube. The high voltage at the tube provides the necessary starting voltage so that it starts and can certainly light up until the thyristor Th1 locks again.

The points J1 and J2 to connect with the two electrodes on one side of the fluorescent tube. The points J3 and J4 , connect with the electrodes on the other side. Now stretch a thin insulated!! Wire along the tube and glue it eg. Scotch tape firmly. This wire carries the ignition voltage of several thousand volts to the tube so that they ignite properly. This wire, connect one end with J7 on the board, while the other end must necessarily be isolated. This wire leads except the high voltage pulses that is also voltage. The points with J5 and J6 of the board is one, tube fitting, ballast clamped to (choke, there’s the light trading.) Finally there is the voltage at J8 and J9. Now it should somehow already shine or flash, with the potentiometer, the flash rate can be set.

100 watt Hiwatt amplifier power supply schematic circuit diagram.

2010-08-31T15:56:00.003+07:00

Download this schematic diagram.

Datasheet semiconductor component download.

1. TC9302
2. BYX94

1 Watt 2.45 GHz Linear Amplifier

2010-08-02T18:27:00.004+07:00

Download this schematic diagram.

Download all parts component list.
Download datasheet semiconductor component. (PDF Format)

1. RF2126

Notes

Part numbers are for reference only. Alternate components may be substituted.

It's also possible to run the RF2126 at around 6.5 volts for slightly more power output. You could try a 7805 voltage regulator with two silicon diodes (or a red LED) in series with the ground lead (cathode to ground). Be sure to isolate the ground tab on the 7805 though or it won't work. You can even just use a plain old 7806 voltage regulator for 6 volts output.

NiCad Battery Charger.

2010-08-01T18:28:00.003+07:00

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. IN4004
2. LM4040
3. 2N3906
4. IRF9530

This array charger ambit is advised for recharging NiCad batteries based on an AC-powered accepted antecedent method. It can crank out as abundant as 1 amp and can be adapted to go alike college by allotment altered accessories for Q1. Since this ambit uses AC band voltages and currents, amuse exercise acute attention during assembly, turn-on, and test. NiCAD batteries accept a accommodation blueprint alleged milliamp-hours. This amount alleged “C” is a admeasurement of how abundant absolute accepted they can accommodate in one hour. Milliamp-hours is addition way to accurate the activity independent in the battery. To recharge a NiCAD array conservatively, it is accepted convenance to pump a accepted of 0.1 C into the anode or absolute terminal for about 12 hours. Therefore, if you had a D-size NiCAD with a accommodation of 4000mAh, you would appetite to allegation it at 400mA for about 12 hours. Addition advantage of this charging address is that it is affable on batteries and doesn’t account them to lose accommodation as bound as the fast allegation techniques.

The achievement accepted of this array charger ambit is controlled by the accretion of the bandgap advertence diode and the base-emitter alliance of the PNP transistor. The PNP transistor provides abrogating acknowledgment to the aboideau of the MOSFET. As acclaimed in the schematic, the batteries actuality answerable can accept a absolute of 12V which is agnate to about 8 NiCAD’s in series. The achievement accepted is bent by the amount of R1 which is bent by:

R1=3.2Volts/Iout

The ability amusement of R1 will equal:

Pr1=3.2Volts*Iout

Be abiding to accommodate pleanty of heatsink for Q1 and accept an appropriately sized resistor for R1. The afterward table summarizes some of the resistor accepted combinations that are possible:

Iout Resistor Amount Resistor Power

100mA 33 ohms 1 watt

500mA 6.2 ohms 2 watt

1Amp 3.3 ohms 5 watt

Cell Phone Battery Meter (3.6 Volt)

2010-08-01T18:12:00.003+07:00

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. LM339
2. TL431

This is a similar circuit to the above and provides a 4 LED bar graph indicating the voltage of a common 3.6 volt Lithium – Ion recharable cell phone battery. The reference voltage is provided by a TL431 programmable voltage source which is set to 3.9 volts where the TL431 connects to the 1K resistor. The lower reference for the LED at pin 14 is set with the 5K adjustable resistor.

The programmed voltage of the TL431 is worked out with a voltage divider (10K 5.6K). The adjustment terminal or junction of the two resistors is always 2.5 volts. So, if we use a 10K resistor from the adjustment terminal to ground, the resistor current will be 2.5/10000 = 250uA. This same current flows through the upper resistor (5.6K) and produces a voltage drop of .00025 * 5600 = 1.4 volts. So the shunt regulated output voltage at the cathode of the TL431 will be 2.5 + 1.4, or 3.9 volts.

Working out the LED voltages, there are three 390 ohm resistors in series with another adjustable (5K) resistor at the bottom. Assuming the bottom resistor is set to 2K ohms, the total resistance is 390+390+390+2000 = 3170 ohms. So, the resistor current is the reference voltage (3.9) divided by the total resistance, or about 3.9/ (390 + 390 + 390 + 2000) equals 1.23 mA. This gives us about .00123*2000= 2.46 volts for the bottom LED, and about .00123*390 = .48 volts for each step above the bottom. So, the LEDs should light at steps of 2.46, 2.94, 3.42, and 3.9. A fully charged cell phone battery is about 4.2 volts. You can adjust the 5.6K resistor to set the top voltage higher or lower, and adjust the lower 5K resistor to set the bottom LED for the lowest voltage. But you do need a 6 to 12 volt or greater battery to power the circuit.

Super Tone Control for Car Audio.

2010-08-01T12:46:00.004+07:00

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. LF353

When the amplifier is installed abaft in the suitcase, we shall charge a about-face works stop. The LA47536 possesses a action angle by in it pin4. This ache crave a baby astriction above to 2V in alpha up the amplifier. Transistor Q1 and Q2 makes the action of walking stop for distance. Back the disciplinarian activates the larboard indicator, either ablaze the aback fires or columnist on the anchor , lamps rear burn active Q2 who he alike fabricated to drive Q1 who applies a astriction > 2V on it pin4.

Fire Alarm Circuit Using LDR

2010-08-01T12:11:00.003+07:00

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. LM7805

2. IN4007

3. BC107

4. UM66

5. TDA2002

Here is a simple fire alarm circuit based on a LDR and lamp pair for sensing the fire.The alarm works by sensing the smoke produced during fire.The circuit produces an audible alarm when the fire breaks out with smoke.

When there is no smoke the light from the bulb will be directly falling on the LDR.The LDR resistance will be low and so the voltage across it (below .6V).The transistor will be OFF and nothing happens.When there is sufficient smoke to mask the light from falling on LDR, the LDR resistance increases and so do the voltage across it.Now the transistor will switch to ON.This gives power to the IC1 and it outputs 5V.This powers the tone generator IC UM66 (IC2) to play a music.This music will be amplified by IC3 (TDA 2002) to drive the speaker.

The diode D1 and D2 in combination drops 1.4 V to give the rated voltage (3.5V ) to UM66 .UM 66 cannot withstand more than 4V.
* The speaker can be a 8Ω tweeter.
* POT R4 can be used to adjust the sensitivity of the alarm.
* POT R3 can be used for varying the volume of the alarm.
* Any general purpose NPN transistor(like BC548,BC148,2N222) can be used for Q1.
* The circuit can be powered from a 9V battery or a 9V DC power supply.
* Instead of bulb you can use a bright LED with a 1K resistor series to it.

Switch Mode Pre-Regulator

2010-08-01T11:39:00.002+07:00

The botheration was that a voltage regulator had to bead the 18 volt capital ability accumulation voltage to 8 volts at 500ma to ability the CD player, crumbling 5 watts of ability and causing a lot of calefaction central the bunched unit. This ambit acts as an interference-free pre-regulator to abundantly abate the ability loss..

The achievement voltage of this ambit is artless by ability band fluctuations. Amount voltage aberration is alone abased on the on-resistance of Q2 and the amount of C2 (re: ripple). The achievement voltage can be set so that the ripple lulls are aloof aloft the drop-out voltage of the beeline regulator at best amount for best activity conservation. The college amount you aces for C2, the added activity you can save and the added abiding the pre-regulator’s achievement voltage.

Download this schematic diagram.

Datasheet semiconductor component. (PDF Format)

1. 2SK2314
2. 2N3904
3. IN4004
4. IN4744
5. IN4148
6. IN5231

LM78XX Positive Regulators Universal PCB for PSU

2010-08-01T11:26:00.005+07:00

The 78XX family is ideally suited for this job, and with this little PCB you can easily build small Power Supplies for virtually every application.

The circuit is very simple:

The Alternating current is applied to X1 and rectifies by B1.

It charges a large Capacitor C1 to power the regulator.

The output voltage depends on the Regulator you use, e.g. 7805, 7812,7815…

Dimensionierung:

C1:4700u, with sufficient voltage Rating!

C2:0.33u

C3:0.1u

Download this schematic diagram.

For download layout on PCB, pleace click here.

Datasheet semiconductor download. (PDF Format)

1. LM78XX

400Watt Audio Power Amplifier with MOSFET BUZ902DP

2010-07-31T12:33:00.004+07:00

Download this schematic diagram.

Datasheet semiconductor component. (PDF Format)

1. BC556
2. 2SB716A
3. 2SD756A
4. BUZ902DP
5. BUZ907DP
6. IN4148

If you like in the sound system or sound this circuit will should like you , This amplifier has two completely separate mono amplifiers with each channel has its own power supply to the order of zero channel crosstalk, a common phenomenon in amplifiers have the same food.

To view the full performance of each supply transformer should be evaluated at 40VAC – 0 – 40VAC at 640VA.

Unlike many models of capacitors is a reservoir to supply the peak currents, I prefer the power transformer in a much faster transient. BUZ902DP Although the specifications are rather modest,

if they can hear you now to experience a large reserve of power available and never any reason to worry that something to do than drive a large number of amplifiers aloud. You do not hear nothing but the truth without distortion at all levels, and I can assure you that this amplifier is required to provide the best features coupled.

Money from imcrew.com

2010-07-27T09:35:00.000+07:00

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imcrew.com penghasil dollar dari internet

2010-07-27T09:27:00.002+07:00

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2009-09-02T08:20:00.001+07:00

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25 Watt MosFet Audio Amplifier

2009-07-06T20:21:00.004+07:00

Click here for download this schematic

Parts:

R1,R4_________47K 1/4W Resistors

R2____________4K7  1/4W Resistor
R3____________1K5  1/4W Resistor
R5__________390R   1/4W Resistor
R6__________470R   1/4W Resistor
R7___________33K   1/4W Resistor
R8__________150K   1/4W Resistor
R9___________15K   1/4W Resistor
R10__________27R   1/4W Resistor
R11_________500R   1/2W Trimmer Cermet
R12,R13,R16__10R   1/4W Resistors
R14,R15_____220R   1/4W Resistors
R17___________8R2    2W Resistor
R18____________R22   4W Resistor (wirewound)

C1___________470nF  63V Polyester Capacitor
C2___________330pF  63V Polystyrene Capacitor
C3,C5________470µF  63V Electrolytic Capacitors
C4,C6,C8,C11_100nF  63V Polyester Capacitors
C7___________100µF  25V Electrolytic Capacitor
C9____________10pF  63V Polystyrene Capacitor
C10____________1µF  63V Polyester Capacitor

Q1-Q5______BC560C   45V 100mA Low noise High gain PNP Transistors
Q6_________BD140    80V 1.5A PNP Transistor
Q7_________BD139    80V 1.5A NPN Transistor
Q8_________IRF530  100V 14A N-Channel Hexfet Transistor
Q9_________IRF9530 100V 12A P-Channel Hexfet Transistor

semiconductor list componen datasheet (PDF Format)

1. BC.560C
2. BD.140
3. BD.139
4. IRF.530
5. IRF.9530

6 Input Mixer

2009-07-06T20:10:00.005+07:00

A simple mixer with 3 line inputs and 3 mic inputs using commonly available parts.

click here for download this schematic diagram

The mixer circuit above has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor. As with any mixer circuit, a slight loss is always introduced. The final summing amplifier has a gain of 2 or 6dB to overcome this. The Input line level should be around 200mV RMS.

The mic inputs are amplified about 100 times or 40dB, the total gain of the mixer including the summing amplifier is 46dB. The mic input is designed for microphones with outputs of about 2mV RMS at 1 meter. Most dynamic microphones meet this standard.

The choice of op-amp is not critical in this circuit. Bipolar, FET input or MOS type op-amps can therefore be used; i.e 741, LF351, TL061, TL071, CA3140 etc. The power supply is a dual positive and negative supply, two 9 Volt batteries may be used as shown above or a power supply is recommended for longer periods of use.

Download list datasheet semiconductor component. (PDF Format)

1. LM741

2. LM324

3. LF351

4. NE5534

5. TL071

High Quality Intercom

2009-07-06T20:03:00.003+07:00

click here for download this schematic diagarm

This circuit consists of two identical intercom units. Each unit contains a power supply, microphone preamplifier, audio amplifier and a Push To Talk (PTT) relay circuit. Only 2 wires are required to connect the units together. Due to the low output impedance of the mic preamp, screened cable is not necessary and ordinary 2 core speaker cable, or bell wire may be used.

The schematic can be broken into 34 parts, power supply, mic preamp, audio amplifierand PTT circuit. The power supply is designed to be left on all the time, which is why no on / off switch is provided. A standard 12 V RMS secondary transformer of 12VA will power the unit. Fuses are provided at the primary input and also secondary, before the rectifier. The 1 A fuse needs to be a slow blow type as it has to handle the peak rectifier current as the power supply electrolytics charge from zero volts.

The microphone amplifier is a 2 transistor direct coupled amplifier. BC108B transistors will work equally well in place of the BC109C transistors. The microphone used is a 3 terminal electret condenser microphone insert. These are popular and require a small current to operate. The preamp is shown in my audio circuit section as well, but has a very high gain and low distortion. The last transistor is biased to around half the supply voltage; this provides the maximum overload margin for loud signals or loud voices. The gain may be adjusted with the 10k preset. Sensitivity is very high, and a ticking clock can easily be heard from the distant loudspeaker.

The amplifier is based on the popular National Semiconductor LM380. A 50 mV input is all thats required to deliver 2W RMS into an 8 ohm loudspeaker. The choice of loudspeaker determines overall sound quality. A small loudspeaker may not produce a lot of bass, I used an old 8 inch radio loudspeaker. The 4.7u capacitor at pin 1 of the LM380 helps filter out any mains hum on the power supply. This can be increased to a 10u capacitor for better power supply rejection ratio.

The push to talk (PTT) circuit is very simple. A SPDT relay is used to switch between mic preamplifier output or loudspeaker input. The normally closed contact is set so that each intercom unit is "listening". The non latching push button switch must be held to talk. The 100u capacitor across the relay has two functions. It prevents the relays back emf from destroying the semiconductors, and also delays the release of the relay. This delay is deliberate, and prevents any last word from being "chopped" off.

Download datasheet semiconductor component. (PDF Format)

1. BC.109C
2. LM.380
3. IN.4001

Micro Power AM Broadcast Transmitter

2009-07-06T19:56:00.004+07:00

download this schematic diagram

download semiconductor list datasheet:

1. 2N3904

2. 74HC14

In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration. The oscillator frequency can be either fixed by a crystal or made adjustable (VFO) with a capacitor/resistor combination. A 100pF capacitor is used in place of the crystal for VFO operation. Amplitude modulation is accomplished with a second transistor that controls the DC voltage to the output stage. The modulator stage is biased so that half the supply voltage or 6 volts is applied to the output stage with no modulation. The output stage is tuned and matched to the antenna with a standard variable 30-365 pF capacitor. Approximately 20 milliamps of current will flow in the antenna lead (at frequencies near the top of the band) when the output stage is optimally tuned to the oscillator frequency. A small 'grain of wheat' lamp is used to indicate antenna current and optimum settings. The 140 uH inductor was made using a 2 inch length of 7/8 inch (OD) PVC pipe wound with 120 turns of #28 copper wire. Best performance is obtained near the high end of the broadcast band (1.6 MHz) since the antenna length is only a very small fraction of a wavelength. Input power to the amplifier is less than 100 milliwatts and antenna length is 3 meters or less which complies with FCC rules. Output power is somewhere in the 40 microwatt range and the signal can be heard approximately 80 feet. Radiated power output can be approximated by working out the antenna radiation resistance and multiplying by the antenna current squared. The radiation resistance for a dipole antenna less than 1/4 wavelength is

R = 80*[(pi)^2]*[(Length/wavelength)^2]*(a factor depending on the form of the current distribution) The factor depending on the current distribution turns out to be [(average current along the rod)/(feed current)]^2 for short rods, which is 1/4 for a linearly-tapered current distribution falling to zero at the ends. Even if the rods are capped with plates, this factor cannot be larger than 1. Substituting values for a 9.8 foot dipole at a frequency of 1.6 MHz we get R= 790*.000354*.25 = .07 Ohms. And the resistance will be only half as much for a monopole or 0.035 Ohms. Radiated power at 20 milliamps works out to about I^2 * R = 14 microwatts.

AM DSB TRANSMITTER FOR HAMS

2009-07-06T19:49:00.002+07:00

download this schematic

download list datasheet semiconductor component. (PDF Format)

1. IN.4148

2. BC.548

3. 2N.2222A

4. SL.100B

The circuit of AM transmitter is designed to transmit (amplitude modulated) DSB (double side band) signals. A modulated AM signal consists of a carrier and two symetrically spaced side bands. The two side bands have the same amplitude and carry the same information. In fact, the carrier itself coveys or carries no information. In a 100% modulated AM signal 2/3 rd of the power is wasted in the carrier and only 1/6th of the power is contained in each side band.

In this transmitter we remove the carrier and transmitt only the two side bands. The effective output of the circuit is three times that of an equivalent AM transmitter.

Op Amp IC741 is used here as a microphone amplifier to amplify the voice picked up by the condenser microphone. The output of the op amp is fed to the double balanced modulator (DBM) build around four IN4148 diodes. The modulation level can be adjusted with the help of preset VR1.

The carrier is generated using crystal oscillator wired around BC548 transistor T2. The carrier is further amplified by transistor T1, which also acts as a buffer between carrier oscillator and the balanced modulator. The working frequency of the transmitter can be changed by using crystals of different frequencies. For multi frequency operation, selection of different crystals can be made using a selector switch.

Ths output of the DBM contains only the product (of audio and carrier) frequencies. The DBM suppresses both the input signals and produces double side band suppressed carrier (DSBSC) at its output. However, since the diodes used in the balanced modulator are not fully matched, the output of the DBM does contain some residual carrier. This is known as carrier leakage. By adjusting the 100 ohm preset VR2 and trimmer C7 you can null the carrier leakage.

To receive DSB signals you need a beat frequency oscillator to reinsert the missing carrier. If you don't have a beat frequency oscillator, or want to transmitt only AM signal, adjust preset VR2 to leak some carrier so that you can receive the signals on any ordinary radio receiver. In AM mode 100% modulation can be attained by adjusting preset VR1 and VR2.

The DSBSC signal available at the output of the balanced modulator is amplified by two stages of RF linear amplifiers. Transistor 2N2222A (T3) is used as an RF pre amplifier, which provides enough signal amplification to drive the final power amplifier build around transistor SL100B. The output of the final power amplifier is connected to the antenna.

All coils are to be wound ferrite balun core (same as used in TV balun transformer of size 1.4 cm * 0.6 cm) using 24 swg enameled copper wire. Proper heat sink should be provided for SL100B transistor used as final power amplifier.

X1 - 8+8 Turns Bifalar 24 SWG On TV Balune Core
X2 - Primary 12 Turns, Secondary 4 Turns. 24 SWG on TV Balun Core (dot indicates start of coil).
X3 - 20 Turns 24 SWG on TV Balun Core

Range of the circuit depends on the type of antenna used. It is very important to use matched antenna to radiate the signals effectively. I used horizontal dipole antenna, which is simple and easy to construct. For 7 MHz, ie 40 meter ham band the length of dipole antenna will be 20 meter. Use 75 Ohms co-axial cable to connect antenna and transmitter. I was able to get 57 report from station 80 kilometer away. You can easily add a Linear RF amplifier using IRF830 to get more power.

Circuit designed by YUJIN BOBY VU3PRX
Published in Electronics For You Dec 2000

5,000W ultra-light, high-power amplifier, without switching-mode power supply

2009-05-31T13:56:00.004+07:00

Download this schematic diagram.

download semiconductor component datasheet. (PDF Format)

1. MPSA.42

2. MPSA.92

3. MPSW.42

4. MPSW.92

5. 2SA1302

6. 2SC3281

7. MJL21193

8.MJL21194

9. LM7815

10. LM7915

This circuit is of an 2x 2,500W RMS stereo amplifier, super-light and without switching-mode power supply. The circuit just shows a channel, and the power supply that it assists to the two channels. The audio circuit should be duplicated, but the power supply assists to the two channels without problems.

A special care should be destined to the insulating transformer of the audio line, that should be of audio-high-quality, of the type used in microphone pre amps input line. The whole group (2 channels) of 5,000W RMS it should not weigh more than 32 lbs, already inside of an appropriate metallic box.

WARNING:

This circuit is exclusively for amateur use. It contains not-isolated parts of the electric AC net and it can be very dangerous. The connections for the speakers are not isolated of the domestic AC net and it requests extra care. This procedure seeks to substitute a conventional power supply with great weight and cost reduction, without necessarily to use a switching-mode power supply.

This procedure cannot be allowed in some countries for commercial-use. The author doesn't have any responsibility for the form as that circuit it will be applied.

LM2577 5V to 12V DC Converter step up Voltage Regulator

2009-05-20T08:17:00.003+07:00

DC to DC step up voltage regulator. Wide input voltage 3.5Vdc to 40Vdc. This is Circuit DC to DC converter step up vol

Download this schematic.

Download list semiconductor datasheet. (PDF Format)

1. LM2577
2. IN5821

http://www.circ uits-lab.com /

Injector Pulse Width Monitor with LM324 ,LM3914

2009-05-20T08:12:00.004+07:00

The schematic for the pulse width monitor. The heart of the circuit is the transistor current source which charges cap C10 to form an integrator. The theory is that the cap is charged and the voltage across it increases linearly for the amount of time that the injector is energized. As the injector is switched off the voltage in C10 is stored in cap C9 and then C10 is reset to 0 volts to get ready for the next cycle. The output of the circuit is the voltage across cap C9, this voltage is fed directly into U3 the bar graph chip to be displayed as a value between 1-10 on the LEDs. Potentiometer R31 sets the charge rate on C10 and basically sets the max injector on time that can be displayed.

Download this schematic diagaram.

download datasheet the semiconductor component. (PDF Format)

1. LM324

2. LM3914

3. CD4058

4. LM7805

5. MN3206

6. MN3906

7. 2N2222

8. IN214

9. IN5233

Injector Pulse Width Monitor with LM324 ,LM3914 - [Link]

Temperature Monitor with IC LM741 or LM301

2009-05-20T08:08:00.004+07:00

Using a thermistor in the position shown makes a heat activated sensor. A change in temperature will alter the output of the opamp and energize the relay and light the LED. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm.

Download this schematic.

Download semiconductor parts datasheet. (PDF Format)

1. LM741

2. LM301

3. BC182B

Temperature Monitor with IC LM741 or LM301 - [Link]

2N3055 Simple inverter 5W

2009-05-20T08:05:00.004+07:00

This simple inverter. The main aim of this circuit is to provide a suitable supply for all kind of low power battery chargers that normally connect to the mains such as mobile phones, electric shavers, etc, even an electronic neon light rated at 5W was successfully connected. Only easily obtainable components are used.

Download this schematic diagram.

Download list datasheet semiconductor parts. (PDF Format)

1. 2N3055

http://www.circuits-lab.com/

Nagative voltage generation using 555 timer

2009-05-20T08:00:00.004+07:00

This 555 timer based PWM controller features almost 0..100% pulse width regulation using R1, while keeping the oscillator frequency relatively stable. The frequency is dependent on values of R1 and C1, values shown will give a frequency range from about 170 to 200 Hz. Any 555 chip will do, CMOS is fine as well. Diodes are not critical, I used 1N4148. Total cost of parts is about $2. As the whole thing is quite trivial, it’s very easy to build on prototyping board like I did.

Download this schematic diagram.

Download semiconductor datasheet parts. (PDF Format)

1. NE555

2. BD140

PWM Speed Motor Controller By IC 555-Electronic control circuit - [Link]

Power Amplifier with STK40xx Series Module

2009-05-20T07:56:00.005+07:00

The series STK40xx is power amplifiers in completed form in a nutshell. They are characterized by the very good quality of sound and their low price. It is easy we make a power amplifier using only few external components. The STKxxxx amplifiers, for them we will find in enough eponymous stereo amplifiers , but also in enough activety loudspeakers. They do not need a lot of special knowledge of manufacture, only that attention in pins, in order to they do not break, and one good power supply. Details for the various types of series, voltage of work and the output power, see the Table A

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. STK 40XX

Power Amplifier with STK40xx Series Module - [Link]

LM317T Voltage Regulator with Pass Transistor

2009-05-20T07:50:00.005+07:00

The LM317T output current can be increased by using an additional power transistor to share a portion of the total current. The amount of current sharing is established with a resistor placed in series with the 317 input and a resistor placed in series with the emitter of the pass transistor.

Download this schematic.

Download list datasheet semiconductor parts. (PDF Format)

1. 2N2955
2. LM317A
3. IN4002

http://www.circuits-lab.com/

Line Driver

2009-05-06T21:20:00.004+07:00

Description:

A stereo line driver for feeding long cables or buffering an audio source.

Download this schematic diagram.

Download semiconductor parts datasheet. (PDF Format)

1. BC109C

Notes

This preamplifier has a low output impedance, and is designed to drive long cables, allowing you to listen to a remote music source without having to buy expensive screened cables. The very low output impedance of around 16 ohms at 1KHz, makes it possible to use ordinary bell wire,loudspeaker or alarm cable for connection. The preamplifier must be placed near the remote music source, for example a CD player. The cable is then run to a remote location where you want to listen. The output of this preamp has a gain of slightly less than one, so an external amplifier must be used to drive loudspeakers.

Buffer Amplifier

2009-05-06T21:15:00.004+07:00

Description:

A hifi preamplifier designed to convert high output impedance amplifiers to 600 ohm outputs.

Download this schematic diagram.

Download this image.

List datasheet semiconductor parts. (PDF Format)

1. BC547C
2. BC557C
3. 2SA1358
4. 2SC3421

TDA2030 8w Amplifier

2009-05-06T21:10:00.005+07:00

Download this schematic diagram.

Download list datasheet semiconductor parts. (PDF Format)

1. TDA2030
2. IN4001

Notes

Although the TDA2030 is capable of delivering 20 watts of audio power, I deliberately reduced the output to about 8 watts to drive 10 watt speakers. This is more than adequate for a smaller room. Input sensitivity is 200mV. Higher input levels naturally will give greater output, but no distortion should be heard. The gain is set by the 47k and 1.5k resistors. The TDA2030 IC is affordable and makes a good replacement amplifier for low to medium audio power systems. Incidentally, it is speaker efficiency that determines how "loud" the sound is. Speaker efficiency or sound pressure level (SPL) is usually quoted in dB/meter. A speaker with an SPL of 97dB/m will sound louder than a speaker with an SPL of 95dB/m.

12 Volt 30 Amp Power Supply

2009-04-20T07:11:00.005+07:00

Download this schematic diagram.

Download list datasheet semiconductor parts. (PDF Format)

1. TIP2955
2. LM7812

Description

Using a single 7812 IC voltage regulator and multiple outboard pass transistors, this power supply can deliver output load currents of up to 30 amps. The design is shown below:

The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so that the regulator can maintain its output. If a transformer is used, then the rectifier diodes must be capable of passing a very high peak forward current, typically 100amps or more. The 7812 IC will only pass 1 amp or less of the output current, the remainder being supplied by the outboard pass transistors. As the circuit is designed to handle loads of up to 30 amps, then six TIP2955 are wired in parallel to meet this demand. The dissipation in each power transistor is one sixth of the total load, but adequate heat sinking is still required. Maximum load current will generate maximum dissipation, so a very large heat sink is required. In considering a heat sink, it may be a good idea to look for either a fan or water cooled heat sink. In the event that the power transistors should fail, then the regulator would have to supply full load current and would fail with catastrophic results. A 1 amp fuse in the regulators output prevents a safeguard. The 400mohm load is for test purposes only and should not be included in the final circuit.

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0 - 300V Adjustable Power Supply.

2009-04-20T07:01:00.004+07:00

Download this schematic.

Download datasheet semiconductor parts. (PDF Format)

1. BUZ326
2. BC547

Introduction

To prevent my high voltage experiments to go up in smoke completely, I designed
a simple circuit which can provide an adjustable voltage source of 0 to 330 Volt..
The supply is short-ciruit proof: the current is limited to about 100mA.

Circuit description

TR1 is a 1:1 mains transformer; it is included for safety.

The mains voltage from TR1 is rectified with bridge D1 (1Amp / 500V) and large elcap C1.

T1 is switched as a source follower: the source of T1 will follow the voltage of the
wiper of R3. D2 is included to protect the gate of T1; although in theory not necessary
I strongly recommend to include it!

T2 and shunt resistor R2 build the current limiter. When the output current becomes too high, T2 will discharge
the gate of T1. This will prevent the current to become too high.
The value of R3 has been determined experimentally; it depends also on the Hfe of T2 so you may need to tune the value of R2.

Note that T1 needs a large heatsink: in worst case T1 will dissipate 330V x 100mA = 33Watt!
Instead of a BUZ 326 (400V/10.5Amp) you can also use an IRF740 (400V/10Amp).
The output impedance of the power supply is determined by the beta of T1, so the larger the MOSFET
the lower the output impedance!

15 Watt Mini Amplifier

2009-04-13T20:33:00.005+07:00

A 15 watt amplifier made using discrete components. Sergio designed this circuit for his Electronics Level II course.

Download this schematic diagram.

Download list datasheet semiconductor component. (PDF Format)

1. 2N3904
2. 2N2907A
3. 2N3906
4. IN4002

Notes:
This amplifier uses a dual 20 Volt power supply and delivers 15 watts RMS into an 8 ohm load. Q1 operates in common emitter, the input signal being passed to the bias chain consisting of Q8, Q9, D6, D13 and D14. Q8 and Q9 provide a constant current through the bias chain to minimize distortion, the output stage formed by a discrete darlington pair (Q2,Q4) and (Q7,Q11). The last two transistors are power Transitors, specifically the 2N3055 and MJ2955. The 7.02K resistor, R16 was made using a series combination of a 4.7K, 680 Ohms, and two 820 Ohms. The 1.1K resistor, R3 was made using a 100 Ohms and a 1K resistor. You can use this circuit with any walkman or CD player since it is designed to take a standard 500mv RMS signal.

http://www.zen22142.zen.co.uk/

100W Guitar Power Amplifier

2009-04-13T20:26:00.006+07:00

The power amp board has remained unchanged since it was first published in 2002. It certainly isn't broken, so there's no reason to fix it. The photo below shows a fully assembled board (available as shown as M27). Using TIP35/36C transistors, the output stage is deliberately massive overkill. This ensures reliability under the most arduous stage conditions. No amplifier can be made immune from everything, but this does come close.

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The power amp (like the previous version) is loosely based on the 60 Watt amp previously published (Project 03), but it has increased gain to match the preamp. Other modifications include the short circuit protection - the two little groups of components next to the bias diodes (D2 and D3). This new version is not massively different from the original, but has adjustable bias, and is designed to provide a "constant current" (i.e. high impedance) output to the speakers - this is achieved using R23 and R26. Note that with this arrangement, the gain will change depending on the load impedance, with lower impedances giving lower power amp gain. This is not a problem, so may safely be ignored.

Should the output be shorted, the constant current output characteristic will provide an initial level of protection, but is not completely foolproof. The short circuit protection will limit the output current to a relatively safe level, but a sustained short will cause the output transistors to fail if the amp is driven hard. The protection is designed not to operate under normal conditions, but will limit the peak output current to about 8.5 Amps. Under these conditions, the internal fuses (or the output transistors) will probably blow if the short is not detected in time.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. BC559

2. BC549

3. BD139

4. BD140

5. TIP35C

6. TIP36C

Guitar Pre-Amplifier

2009-04-13T20:20:00.006+07:00

A photo of the Revision-A preamp is shown below. You'll see that there are two dual opamps, but the schematic only shows one. This is the main part of the Rev-A update - the output section now has gain (which is easily selected), and a better buffered low output impedance. The remainder of the circuit is unchanged. Full details of the new version are available on the secure site for those who purchase the PCBs.

Download this image.

The preamp circuit is shown in Figure 1, and has a few interesting characteristics that separate it from the "normal" - assuming that there is such a thing. This is simple but elegant design, that provides excellent tonal range. The gain structure is designed to provide a huge amount of gain, which is ideal for those guitarists who like to get that fully distorted "fat" sound.

However, with a couple of simple changes, the preamp can be tamed to suit just about any style of playing. Likewise, the tone controls as shown have sufficient range to cover almost anything from an electrified violin to a bass guitar - The response can be limited if you wish (by experimenting with the tone control capacitor values), but I suggest that you try it "as is" before making any changes.

Download this schematic diagram.

semiconductor datasheet component. (PDF Format)

1. TL072
2. BC549

Automatic Loudness Control

2009-04-13T08:09:00.002+07:00

In order to obtain a good audio reproduction at different listening levels, a different tone-controls setting should be necessary to suit the well known behaviour of the human ear. In fact, the human ear sensitivity varies in a non-linear manner through the entire audible frequency band, as shown by Fletcher-Munson curves.
A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels.
Fortunately, the human ear is not too critical, so a rather simple circuit can provide a satisfactory performance through a 40dB range.
The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7.
Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below.
C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.

Technical data:

Frequency response referred to 1KHz and different control knob positions:

Total harmonic distortion at all frequencies and 1V RMS output: <0.01%

Notes:

SW1 is shown in "Control flat" position.
Schematic shows left channel only, therefore for stereo operation all parts must be doubled except IC1, C6 and C8.
Numbers in parentheses show IC1 right channel pin connections.
R7 should be set to obtain maximum undistorted output power from the amplifier with a standard music programme source and P1 rotated fully clockwise.

9v Battery Voltage Monitor using a LTC1440 Comparator

2009-04-13T08:02:00.004+07:00

This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts. It uses a LTC1440 comparator, which also contains a 1.18v reference diode. In standby mode, the circuit draws only 4uA.

Battery Monitor Circuits
Master Schematic Category List - David A. Johnson, P.E.

120 VAC Lamp Dimmer

2009-04-10T19:09:00.003+07:00

The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF capacitor reaches about 8 volts, the transistors will switch on and discharge the capacitor through the SCR gate causing it to begin conducting. The time delay from the beginning of each half cycle to the point where the SCR switches on is controlled by the 50K resistor which adjusts the time required for the 2uF capacitor to charge to 8 volts. As the resistance is reduced, the time is reduced and the SCR will conduct earlier during each half cycle which applies a greater average voltage across the load. With the resistance set to minimum the SCR will trigger when the voltage rises to about 40 volts or 15 degrees into the cycle. To compensate for component tollerances, the 15K resistor can be adjusted slightly so that the output voltage is near zero when the 50K pot is set to maximum. Increasing the 15K resistor will reduce the setting of the 50K pot for minimum output and visa versa. Be careful not to touch the circuit while it is connected to the AC line.

visit: http://www.discovercircuits.com/list.htm

Variable Voltage and Current Power Supply

2009-04-10T19:06:00.005+07:00

Download this schematic.

Download list datasheet semiconductor parts. (PDF Format)

1. 2N3055
2. LM1458

Another method of using opamps to regulate a power supply is shown below. The power transformer requires an additional winding to supply the op-amps with a bipolar voltage (+/- 8 volts), and the negative voltage is also used to generate a reference voltage below ground so that the output voltage can be adjusted all the way down to 0. Current limiting is accomplished by sensing the voltage drop across a small resistor placed in series with the negative supply line. As the current increases, the voltage at the wiper of the 500 ohm pot rises until it becomes equal or slightly more positive than the voltage at the (+) input of the opamp. The opamp output then moves negative and reduces the voltage at the base of the 2N3053 transistor which in turn reduces the current to the 2N3055 pass transistor so that the current stays at a constant level even if the supply is shorted. Current limiting range is about 0 - 3 amps with components shown. The TIP32 and 2N3055 pass transistors should be mounted on suitable heat sinks and the 0.2 ohm current sensing resistor should be rated at 2 watts or more. The heat produced by the pass transistor will be the product of the difference in voltage between the input and output, and the load current. So, for example if the input voltage (at the collector of the pass transistor) is 25 and the output is adjusted for 6 volts and the load is drawing 1 amp, the heat dissipated by the pass transistor would be (25-6) * 1 = 19 watts. In the circuit below, the switch could be set to the 18 volt position to reduce the heat generated to about 12 watts.

http://www.discovercircuits.com/list.htm

Variable 3 - 24 Volt / 3 Amp Power Supply

2009-04-10T19:01:00.004+07:00

This regulated power supply can be adjusted from 3 to 25 volts and is current limited to 2 amps as shown, but may be increased to 3 amps or more by selecting a smaller current sense resistor (0.3 ohm). The 2N3055 and 2N3053 transistors should be mounted on suitable heat sinks and the current sense resistor should be rated at 3 watts or more. Voltage regulation is controlled by 1/2 of a 1558 or 1458 op-amp. The 1458 may be substituted in the circuit below, but it is recommended the supply voltage to pin 8 be limited to 30 VDC, which can be accomplished by adding a 6.2 volt zener or 5.1 K resistor in series with pin 8. The maximum DC supply voltage for the 1458 and 1558 is 36 and 44 respectively. The power transformer should be capable of the desired current while maintaining an input voltage at least 4 volts higher than the desired output, but not exceeding the maximum supply voltage of the op-amp under minimal load conditions. The power transformer shown is a center tapped 25.2 volt AC / 2 amp unit that will provide regulated outputs of 24 volts at 0.7 amps, 15 volts at 2 amps, or 6 volts at 3 amps. The 3 amp output is obtained using the center tap of the transformer with the switch in the 18 volt position. All components should be available at Radio Shack with the exception of the 1558 op-amp.

Download this schematic.

Download datasheet semiconductor component. (PDF Format)

1. 2N3055
2. 2N3053
3. 2N3904
4. LM1558

0-30V Stabilized Variable Power Supply with Current Control

2009-04-05T21:01:00.002+07:00

This is high quality stabilized power supply circuit diagram. You will able to adjust the output voltage from 0 volt up to 30 volt DC. You also able to adjust the current output value from 0.002 A to 3 A.

Detail explanation include the PCB layout, visit this page

Flashing Heart Circuit

2009-04-05T20:55:00.004+07:00

This is LED flashing circuit, the circuit is quite simple. Alternatively, you could be create another shape, not just heart shape.

Download this schematic.

Component list:

Resistors
R1, R2	-	470 ohm, 1/2-watt
R3-R5	-	100 ohm, 3-watt
R6-R8	-	1000 ohm, 1.4-watt
R9	-	5000 ohm potentiometer

Capacitors
C1, C2	-	100uF, 16 volts, electrolytic radial

Semiconductors
IC1	-	4047, low power monostable/astable multivibrator
Q1-Q3	-	2n3643 NPN transistor or equivalent
Download datasheet semiconductor component: 1. 4047 2. 2N3643
Diodes
LED1-LED84	-	yellow light-emitting diode
LED85-LED126	-	red light-emitting diode
LED127-LED142	-	green light-emitting diode

Other components
PS1	-	12VDC @ 500mA wall transformer

Miscellaneous: Jumper wire, solder, printed circuit board,
drill and bits,14 pin I.C. socket, and a frame or case.

Capacitor Explanation

2009-04-05T07:16:00.004+07:00

A capacitor is a passive electrical component that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. A capacitor's ability to store charge is measured by its capacitance, in units of farads.

Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters. Practical capacitors have series resistance, internal leakage of charge, series inductance and other non-ideal properties not found in a theoretical, ideal, capacitor.

The capacitor is used in almost every electronic circuit. It is a very important component and it does many different things, depending on where it is placed.

A capacitor is basically a device that stores a charge of electricity.
It has two or more plates that are separated by air or a non conducting medium such as plastic.

A basic capacitor is shown in the diagram below with the corresponding circuit symbol.

Capacitors can be large or small and the size is the result of the value of the capacitor as well as the voltage it is capable of withstanding.

There is a lot to learn about capacitors and we will only be discussing the very basics.
There are many types of capacitors, here are 5 of the most common types:

AIR - such as a tuning capacitor in a radio.

GREENCAP - a polyester capacitor.

CERAMIC - a ceramic insulating material that produces a very compact
capacitor

MONOBLOCK - also called monolithic - a multi-cceramic capacitor

ELECTROLYTIC - aluminium plates with a moist insulating medium. This type of capacitor has a very high capacitance in a small space.

The diagram below shows a single-ended electrolytic, suitable for mounting on a printed circuit board and the symbol.

The unit for capacitance is the FARAD. But one Farad is an enormous value and we don't use values this large in electronics. The value we use is the micro-farad. A microfarad is one-millionth of a farad.

For some circuits we need capacitors of more than 1 microfarad capacitance and for others we need less than 1 microfarad.

For a power supply we need electrolytics of 10 microfarad, 100 microfarad, 1,000 microfarad and even 10,000 microfarad. The letter to signify microfarad is "uF" or simply "u". Thus 1microfarad is 1u, 10 microfarad is 10u etc.

For audio work we need smaller values such as .1microfarad and .01 microfarad.
In electronics, we try and avoid using the decimal point as it can be rubbed off components and omitted from photocopies of circuit diagrams.

To get around this we use sub-multiples and the sub-multiple of microfarad is nanofarad.

1,000 nanofarad = 1 microfarad.
Thus .1u = 100 nanofarad.
The letter to represent nanofarad is "n".
Thus .01u = 10n

For radio frequency work, even smaller values of capacitance are needed.

The nanofarad is divided into 1,000 parts called picofarad. Thus 1,000 picofarad = 1nanofarad.

The picofarad is written pF or simply "p."
Thus 1,000p = 1n.

Some capacitors are physically very small and there is very little space to write the component value. To get around this, manufacturers have produced a numbering system using 3 digits.

It is based on picofarads. A 100 picofarad capacitor is written as 101, A 1,000 picofarad capacitor is written 102, A 10 nanofarad capacitor is written 103 and 100 nanofarads is written 104. The third digit represents the number of zero's.

For example: 1n = 1,000p = 102.
10n = 10,000 = 103
100n = 100,000 = 104

2 Way Cross-Over 3500 Hz (bass and treble)

2009-04-05T07:09:00.004+07:00

This is 2 way cross-over for your speaker system. This circuit will handle 2 speaker that are woofer (low frequency) an tweeter (high frequency).

The result will shown as below picture:

Here the schematic diagram of the circuit:

Audio Clipping indicator.

2009-03-31T05:48:00.004+07:00

It's possible to build a clipping indicator like accesory for amplifier which detects amplifier limitation, when output transistors are fully opened and signal is cutted close to power supply voltage. In this case is acoustic signal distorted in a power amplifier. Circuit as usually is from authors pages. I redraw them in a Eagle and I designed circuit board for two channels. I added place for two LEDs for power supply voltage indicators. This board have small pads, which is not much good. Eagle has these pads too small in default state.

Schematics diagram

Download this schematic

Semiconductor list datasheet download. (PDF Format)

1. BC639
2. BC640

Testing

First we must to test power supply part. Fuses F2 to F5 we leave out and for sure we check again circuit of rectifier and capacitor polarity. a zkontrolujeme pro jistotu zapojení usměrňovače a polaritu kondenzátorů. Possible error can be fatal. If is all OK, that on capacitors will be voltage about 51V. Exact voltage depends on used transformer and power line voltage. After disconnecting will be voltage on capacitor for a long time. We can discharge them with a resistor 100R 2W. It's possible, that with power-on blows fuse F1 even all is OK. In my situation is charging current too big, that I had place NTC thermistor in a series with primary transformer side. I get them from old PC power supply, where it has identical function. Better idea is to use "soft start" circuit, which is made from big resistor on primary side of transformer and relay, which short-circuit resistor after few seconds. I didn't found any circuit which I liked it.

When the power supply works correctly, we can go to test amplifier. First we set trmmer P1 to one end position with maximum resistance. In to the fuse holders for one channel we place resistors 100R 1/4W. With disconnected output and input we can power-on amplifier. On the resistor we would measure maximally 2.5V, which matches current 25mA. If is everything allright, we wait for discharging after power-off and replace resistor with fuses. Initially for testing we can use smaller values. I had switched two wires from power transistors on one channel and resistors smokes and smells. Really is better to everything double check.

Now we must set the bias current. Use amperemeter in place of F2. Turn the trimmer P1, until is current 100mA. How amplifier warming-up current is changing. Regulate current value when it is stabilized, which can be after 15 minutes. Identical procedure repeat for second channel.

With disconnected input we can measure DC offset on the output. In my example I measured 19mV on left channel and 22mV on right channel.

Now we can made regular tests and connects speakers and signal source. I tested with connecting of the amplifier input directly on the output of soundcard. You must carefully increase volume, because amplifier has enough power to destroy small speakers.

Power supply for the 40 W single chip amplifier.

2009-03-30T21:19:00.001+07:00

Constructing the power supply for this amplifier is simple. As shown on the schematic above you need to wire up a 18-0-18 (center tapped) transformer in order to get the recommended +/- 25V. Be very careful since this construction involves mains wiring.

1-chip 40 watt amplifier.

2009-03-30T21:16:00.004+07:00

This is a compact, easy to build amplifier that uses one IC only but delivers 40 watts of audio power. It is ideal for amplifying audio from your mobile CD player or iPod. The chip being used here is the TDA1514 originally brought to the market by Phillips/Valvo. The best characteristics of this chip is its high output power and robustness. It is available in a 9-pin SIL plastic package with a metal mount.

Its package has a heat resistance of less than 1.5K/W. This means that the heatsink must have a heat resistance of only 3.8K/W when the chip reaches its maximum power dissipation of 19W (at Ub = +/-27.5V, Tu = 50⁰C).
One can see from the diagram that only a handful of passive elements are needed to build the chip into a powerful audio amplifier. The power supply as supplied must be able to deliver a current of at least 3 amperes. The standby current consumption is about 60 mA. The supply voltage must never go beyond 27.5 volts!

In building the circuit, keep the wires to the power supply and outputs as short as possible. The resistos R4 and R5 set the voltage gain at the feedback which, in this case, is between 20 and 46 dB.
For a single channel amplifier(mono), a 80 VA transformer (T1) should be sufficient. If you construct two channels (or stereo) amps, 120 VA is recommended. Capacitors Cx and Cy should be at least 4.700uF rated at 35V. It can be up to 10.000uF. Capacitors twice as large discharge slower giving better peak power potential resulting to better power output. Feel free to increase the capacitance but take note that you may not get much additional benefit for the price involved. Make sure they are connected the right way around too or they will blow and cause injury.

Download this schematic diagram.

Semiconductor datasheet component. (PDF Format)

1. TDA 1514

TV Modulator (Exiter) with MC1374

2009-03-30T20:17:00.006+07:00

The MC1374 includes an FM audio modulator, sound carrier oscillator, RF oscillator, and RF dual input modulator. It is designed to generate a TV signal transmitter from audio and video inputs. The MC1374’s wide dynamic range and low distortion audio make it particularly well suited for applications such as video tape recorders, video disc players, TV games and subscription decoders.

Download this schematic diagram.

Semiconductor list datasheet download. (PDF Format)

1. MC1374
2. MPN3404
3. IN914

The MC1374 contains an RF oscillator, RF modulator, and a phase shift type FM modulator, arranged to permit good printed circuit layout of a complete TV modulation system. The RF oscillator is similar to the one used in MC1373, and is coupled internally in the same way. Its frequency is controlled by an external tank on Pins 6 and 7, or by a crystal circuit, and will operate to approximately 105 MHz. The video modulator
is a balanced type as used in the well known MC1496. Modulated sound carrier and composite video information can be put in separately on Pins 1 and 11 to minimize unwanted crosstalk. A single resistor on Pins 12 and 13 is selected to set the modulator gain. The RF output at Pin 9 is a current source which drives a load connected from Pin 9 to V_CC.

Op Amp Radio

2009-03-28T17:33:00.003+07:00

Here is a simple

radio that is easy to build and inexpensive. In fact, you probobly have all the parts you need in your junk box. You will be suprised at the great reception with this little set.

Notes

The antenna can be a piece of wire or a telescoping antenna. 18 inches is a good length for in the city.

The tuning capacitor is a regular broadcast band tuning capacitor. I got mine from a junked AM radio. I got the loopstick antenna from that same radio.

You can change L1 and C1 to recieve different bands (eg. Shortwave). To recieve shortwave, try this: Make L1 30 turns of 30 guage wire wound on a film can and make C1 a 10-365pf capacitor.

Combine this circuit and the 8 Watt Audio Amp for a really neat radio.

The circuit diagram for a 4 bit TTL counter, a type of state machine.

2009-03-28T17:13:00.004+07:00

A circuit diagram (also known as an electrical diagram, wiring diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.

Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire connections being used. The diagram does not show the physical arrangement of components. A drawing meant to depict what the physical arrangement of the wires and the components they connect is called "artwork" or "layout" or the "physical design."

Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.

Download this schematic diagram.

Semiconductor datasheet download. (PDF Format)

1. 74SL107D

2. 74LS08D

For detail, please visit http://en.wikipedia.org

Christmas Decoration Project

2009-03-23T18:18:00.004+07:00

This project flashes 18 LEDs at three different rates and you can use these to create a Christmas decoration of your choice. The circuit is kept simple (and cheap!) by using the 4060B IC which is a counter and oscillator (clock) in one package. The circuit requires a 9V supply, such as a PP3 battery. It will not work with lower voltages and a higher voltage will destroy the LEDs.

The preset variable resistor can be used to adjust the oscillator frequency and this determines the flash rate of the LEDs. The IC limits the current to and from its outputs so the LEDs can be safely connected without resistors in series to limit the current. The stripboard part of the circuit is easy to build but the wiring for the LEDs needs care so detailed instructions are provided below.

Download this schematic diagram.

Parts Required

resistors: 10k, 470k
preset: 47k (this could be 100k if necessary)
capacitor: 0.1µF
4060B IC
16-pin DIL socket for IC
LEDs × 18, 5mm diameter, any mix of colours: red, orange, amber, yellow or green
on/off switch
battery clip for 9V PP3
stripboard 13 rows × 18 holes

Download list datasheet semiconductor parts. (PDF Format)

1. CD4060B

Voltage Regulator 5V-20V Project.

2009-03-23T06:53:00.005+07:00

If you are looking for a low drop voltage regulator that is able to provide a power supply of 1A with an output voltage of between 5V and 20V DC, National Semiconductor LM2941 Low Dropout Adjustable Regulator is one that you can choose to use. It has a typical dropout voltage of 0.5V which means that the input supply need only have to be 0.5V DC more than the desired output voltage. Its other features include internal short circuit current limit and reverse battery protection. As shown in the schematic below, the regulator has 5 pins which consists of the ON/OFF control, Input Voltage, Output Voltage, Ground and Adjustable pins. ON/OFF is used for the purpose of switching on and off of the regulator. The capacitors C1 and E1 are to be placed as close as possible to the regulator.

Download this schematic diagram.

The output of the circuit can be varied by varying the value of potentiometer VR1 from 5V DC to 20V DC. The input voltage is limited from 5.5V DC to 30V DC. Resistor R1 must be greater than 1K. The value of the VR1 that needs to be set is calculated from the formula given below:

VR1 = R1[(Vout/1.275) - 1] ohm

If R1=1K, Vout = 5V, VR1 should be set to 2.9K ohm.

If R1=1K, Vout = 20V, VR1 should be set to 14.7K ohm

Datasheet semiconductor component download. (PDF Format)

1. LM2941CT

Electronic Timer Switch.

2009-03-23T06:42:00.007+07:00

This electronic timer switch project is a good project to build to simulate the presence of occupants in a house. In these days when security is becoming more of a concern when no one is at home, having this device will deter the thief from breaking in. When power up, after 60 minutes, the relay will turn ON for 100 secs, OFF for the next 100 secs, and ON again for 100 secs before OFF again for the next 60 mins. This sequence will be repeated. A device such as a lamp that is connected to the relay will turn ON and OFF according to this timing.

Schematic Diagram

The schematic of the project is as shown below.

Download this schematic diagram.

Parts List

Download datasheet semiconductor component. (PDF Format)

1. CD4060B
2. IN4148
3. IN4003
4. 2SC2002

Vox Amplifier model AC100 Schematic Diagram

2009-03-22T08:01:00.004+07:00

Vox Amplifier model AC100 circuit diagram

Download this schematic diagram.

For detail this circuit, visit schematics.ca

Resistor color code

2009-03-15T21:00:00.002+07:00

The calculator above will display the value, the tolerance and performs a simple check to verify if the calculated resistance matches one of the EIA standard values. Select the first 3 or 4 bands for 20%, 10% or 5% resistors and all 5 bands for precision (2% or less), 5-band resistors. Hover above the tolerance for min. and max. range values.

If you want to find out the color bands for a value, use the tool on the left. Enter the value, select the multiplier (Ω, K or M), the desired precision and hit 'Display resistor' or ENTER. You can also type in resistor values in shorthand notation like 1k5, 4M7 or 100R.

Standard EIA Decade Resistor Values:

E6 series: (20% tolerance)
10, 15, 22, 33, 47, 68

E12 series: (10% tolerance)
10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82

E24 series: (5% tolerance)
10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91

E48 series: (2% tolerance)
100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205, 215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442, 464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953

E96 series: (1% tolerance)
100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210, 215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976

E192 series: (0.5, 0.25, 0.1 and 0.05% tolerance)
100, 101, 102, 104, 105, 106, 107, 109, 110, 111, 113, 114, 115, 117, 118, 120, 121, 123, 124, 126, 127, 129, 130, 132, 133, 135, 137, 138, 140, 142, 143, 145, 147, 149, 150, 152, 154, 156, 158, 160, 162, 164, 165, 167, 169, 172, 174, 176, 178, 180, 182, 184, 187, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213, 215, 218, 221, 223, 226, 229, 232, 234, 237, 240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 271, 274, 277, 280, 284, 287, 291, 294, 298, 301, 305, 309, 312, 316, 320, 324, 328, 332, 336, 340, 344, 348, 352, 357, 361, 365, 370, 374, 379, 383, 388, 392, 397, 402, 407, 412, 417, 422, 427, 432, 437, 442, 448, 453, 459, 464, 470, 475, 481, 487, 493, 499, 505, 511, 517, 523, 530, 536, 542, 549, 556, 562, 569, 576, 583, 590, 597, 604, 612, 619, 626, 634, 642, 649, 657, 665, 673, 681, 690, 698, 706, 715, 723, 732, 741, 750, 759, 768, 777, 787, 796, 806, 816, 825, 835, 845, 856, 866, 876, 887, 898, 909, 920, 931, 942, 953, 965, 976, 988

http://www.hobby-hour.com

Infrared Modulation Identifier

2009-03-14T18:33:00.003+07:00

This is the schematic of Infrared Modulation Identifier Via Remote Control.

Download this schematic diagram.

Download datashet semiconductor component. (PDF Format)

1. BC549C

The circuit illustrates how the modulated carrier of infrared is measured by displaying the waveform on a frequency counter after the signal received is amplified.

Current Expanded Regulated Power Supply

2009-03-14T06:34:00.003+07:00

Actually, this is ordinary regulated power supply, but the current expander using a transistor make this power supply become powerful.

Based on the datasheet, the stabilizer IC’s can deliver up to 1A output current. For example 78xx series regulators are available in different voltage ratings, but in any case the current should not exceed 1A.

The transistor Q1 (2N 29055) used here has 5A current capacity. The resistor R1 is used to keep the current through regulator IC below 300mA. When the current through R1 increases the base current of Q1 (2N 29055) also increases & the load required load current flows through this transistor. By this way a current greater than the capacity of the regulator IC can be delivered to the load. The C1 is used to filter the ripples off the rectifier output.

Download this schematic diagram.

Notes:

Assemble the circuit on good quality PCB.
T1 can be a 230V primary,15V/1A secondary, step down transformer.
If 1 A bridge is not available, make one using four 1N 4007 diodes.
The series regulator IC should be selected according to the desired output voltage.

IC 7805 for 05V
IC 7806 for 06V
IC 7809 for 09V
IC 7812 for 12V

Semiconductor datasheet download. (PDF Format)

1. LM78XX
2. 2N2955

Digital Volume Controller

2009-03-13T22:08:00.003+07:00

If you need digital volume control, then this circuit will great for you. Just press the button and you will be able to increase and decrease the volume level. This circuit is for 1 kanal only. For stereo audio, you need to build 2 similiar circuit and use push button switch which have double input and double output.

Download this schematic diagram.

Datasheet semiconductor download. (PDF Format)

1. DS1669

Loudspeaker System Crossover Network

2009-03-13T22:03:00.003+07:00

Building a crossover for your speaker system is easy. Here the schematic diagram:

Notes:

Capacitor must be non-polar capacitor types with a voltage rating of 50 volt or more (preferably 100 volt).
Capacitor may be paralled to achieve specified values.
Inductors should be air core. Do not mount inductors in top of each other.
Resistors should be 100 Watts or more.

Download the schematic diagram in PDF format

800W Audio Amplifier with MOSFET

2009-03-13T21:57:00.003+07:00

Here the schematic diagram of 800 watt audio amplifier with MOSFET.

This amplifier can be used for practically any application that requires high power, low noise, distortion and excellent sound. Examples would be Sub-woofer amp, FOH stage amplifier, One channel of a very high-powered surround sound amplifier etc.

For detail explanation about how this circuit works include the large schematic diagram, power supply schematic diagram and complete component listing, download this complete article

http://circuitdiagram.net

Power Supply 1.3 - 32 V / 5A with Short Circuit Protection

2009-03-13T11:59:00.004+07:00

This is a very easy to build power supply that is based on LM338 5A adjustable voltage regulator. I am using the supply for a long time, have no problem yet. Only current adjust is missing but I overcome this situation by using an LCD panel ampermeter. There is no PCB for the circuit. I took a 3x16 copper plate and strip the unused areas by a knife. If you want you can use analog meters instead of LCD panels.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. LM338

2. IN4002

Notes:

Use thick wires for connections.
When connecting the LM338 to the heatsink use thermal paste.
Use external supplies for LCD panels. They can be 9V batteries. The panels I use draws 1mA current and the batteries last sufficiently long time. If you have small transformers which can supply regulated 9V, you can use them. You need separate transformers for each panel!
The transformer should be 100 Watt but if you don't need high current you can try transformers that you already have. (I can draw 6A from 100Watt transformer.)
If you have multi winding transformer you can use the diode connections shown in schematic. Diodes must be 10-15 A.
Be careful while connecting LM338. Don't put it inverse.
Output of your transformer mustn't exceed 25V AC...

60 Watt Amplifier using TDA2052

2009-03-13T11:48:00.004+07:00

This is HiFi audio amplifier system. This amplifier is AB class amplifier and has very low distortion that's why this amplifier can be used for HiFi audio system. TDA2052 has mute and st-by functions so it can be controlled by external digital circuits. Very high temperature and output short circuit protections are included. You should use a heatsink to dissipate the excess heat.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. TDA2052

Functions of the Components:

R1 - Input Impedance
R2,R3 - Gain (32dB)
R4 - Input Impedance in Mute Mode
R5 - Standby Transition Time
R8 - Output Frequency Balancing
R9,R10 - Discharge Resistors
C1 - Input Coupling Capacitor
C3 - Feedback Coupling Capacitor
C4 - Standby Transition Time
C5 - Output Frequency Balancing
C6,C7 - Supply Stabilizing Capacitors
C9,C10 - Supply Filter Capacitors

Component List:

Component	Value	Number
R1,R2,R4,R5	11k ¼ W	4
R3	560, ¼ W	1
R6	7.5 K, ¼ W	1
R7	1 K, ¼ W	1
R8	4.7 , ¼ W	1
R9,R10	1.2 K, ¼ W	2
C1	2 uF/25 V	1
C3,C4	10 uF/25 V	2
C5,C9,C10	100 nF	3
C6,C7	1000 uF/40 V	1
U1	TDA2052	1

10 Band Graphic Equalizer

2009-03-13T11:24:00.004+07:00

Download this schematic diagram.

This is 10 band graphic equalizer for one channel (mono) audio system. You need build 2 similiar circuits for 2 channel (stereo) audio system.

This equalizer build based on TL074 low noise JFET op-amp which will give you high quality audio output.

Transistorized Inverter 60W 12V DC to 230V AC

2009-03-12T16:40:00.006+07:00

Download this schematic.

Download datasheet semiconductor component. (PDF Format)

1. BC548
2. BD140
3. 2N6107
4. 2N3055

This is low cost fully transistorised inverter circuit capable of driving medium loads of the order of 40 to 60 watts using battery of 12V, 15 Ah or higher capacity.

Transistors T1 and T2 (BC548) form a 50Hz multivibrator. For obtaining correct frequency, the values of resistors R3 and R4 may have to be changed after testing. The complementary outputs from collectors of transistors T1 and T2 are given to PNP darlington driver stages formed by transistor pairs T3-T4 and T6-T7 (utilising transistors BD140 and 2N6107). The outputs from the drivers are fed to transistors T5 and T8 (2N3055) connected for push-pull operation.

Somewhat higher wattage can be achieved by increasing the drive to 2N3055 transistors (by lowering the value of resistors R7 and R8 while increasing their wattage). Suitable heatsinks may be used for the output stage transistors. Transformer X1 is a 230V primary to 9V-0-9V, 10A secondary used in reverse.

Inverter 100W, 12V DC to 220V AC

2009-03-12T16:35:00.004+07:00

Here is 100 Watt Inverter 12V DC to 220V AC schematic diagram.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. CD4047
2. TIP122
3. 2N3055

Low Impedance Microphone Amplifier

2009-03-12T16:28:00.004+07:00

You can download the schematic, pcb layout and component list from here

Download this schematic diagram.

This circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones.
It will work with stabilized voltages between 6-30VDC. If you don’t build the impedance adapter part with T1, you get a mic-amp for higher impedance microphones. In this case, you should directly connect the signal to C7.

Component list:

R1=15k	C1= 3k9	U1= TL081
R2= 150k	C2= 100u	D1= 1N4148
R3= 2k2	C3= 22u	CN1= SIL6
R4= 820	C4= 4u7
R6= 10k	C5= 470u
R7= 10k	C6= 10u
P1= 1M	C7= 100n
	C8= 47u UNIPOLAR

2000W Stereo Audio Power Amplifier

2009-03-12T16:15:00.004+07:00

Click here for download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. BF245A

2. BF256C

3. BC639

4. BC640

5. BC550

6. BC560

7. BD711

8. BD712

9. BF871

10. BF872

11. BD139

12. BD140

13. MJE340

14. MJE350

15. 2SC5171

16. 2SA1930

17. 2SA1987

18. 2SC5359

This is linear amplifier which need advance knowledge in electronics since the schematic diagram is very complex for hand made circuit.

Download the zipped schematic here

DipTrace Free 1.30

2009-03-12T15:57:00.006+07:00

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DipT race is an advanced PCB design software application that consists of 4 modules: PCB Layout with efficient auto-router, Schematic Capture, Component and Pattern Editors that allow you to design your own component libraries. Besides being very easy-to-use, which is rare for a PCB design tool, this software possesses a very intuitive user interface and many innovative features. Output formats are DXF, Gerber, N/C Drill and G-code.

60W Power Audio Amplifier with 2N3055

2009-03-11T20:07:00.003+07:00

Download this schematic diagram.

Download darasheet semiconductor component. (PDF Format)

1. 2N3055
2. BC286
3. BC287
4. BC187
5. BC717

This is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500Ω trimmer resistor. As this current incrases, the sound of the amplifier gets better, but the end transistors are more heating. But if this current decrases, the transistors are not heating so much, but the sound gets worse.

TV Transmitter.

2009-03-11T15:39:00.003+07:00

Download this schematic diagram.

Semiconductor datasheet component download.

1. BC547

Description:
A VHF band TV transmitter using negative sound modulation and PAL video modulation. This is suitable for countries using TV systems B and G.

Notes:
The frequency of the transmitter lies within VHF and VLF range on the TV channel, however this circuit has not been tested at UHF frequencies. The modulated sound signal contains 5.5 -6MHz by tuning C5. Sound modulation is FM and is compatible with UK System I sound. The transmitter however is working at VHF frequencies between 54 and 216MHz and therefore compatible only with countries using Pal System B and Pal System G.

13 Volt 20 Amp PSU

2009-03-11T15:28:00.004+07:00

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. BC557
2. BD330
3. 2N5683
4. BC547
5. BUZ11

Notes:

This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added.

The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation.

The rectified current will be “ironed” by the C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend 50.000uF. This capacity can be built up by several smaller capacitors in parallel.

The base of this design is a simple 12V regulator (7812). The output voltage can be brought to desired value (here 13.8V) by two external resistors (R5 and R6) using this formula:

U= 12(1+R5/R6)

The low currents (here 15mA) will keep the 7812 in its regular function. As soon as the current rises over 15ma, the voltage drop on R4 will “open” the Q3, actually handling the high output current. This is a PNP transistor (Ic>25) and current amplification factor of at least 20. The one that has been tested and proven here is the 2N5683.

The current limiting resistance RL, for the maximum output of 20 Amps should be 0.03 Ohms, rated at least 15W. You can use the resistance wire or switch several resistors in parallel, totaling the resistance/power values. Values for other currents can be calculated by the rule:

RL=0.7/Imax

The RL and Q2 (3A PNP such as BD330) form a short circuit “automatic fuse”. As soon as the maximum current reaches 20Amps, the voltage drop over the resistor RL will open Q2, and thus limit the B-E Current of Q3. Parallel to Q2 is Q1, which lights the LED 1 whenever the current limiting circuit is active. When the “fuse” is active, the Q2 bridges the R3, so the full current would flow through the IC1, and damage it. Therefore the R4 is inserted, as to limit the IC1 current to 15mA. This makes it possible to run the IC1 without any cooling aid.

The LED 2 will light up every time the PSU is switched on.

There is an adjustable current limiter in parallel to the fixed output, thus providing adjustable current source for smaller currents.

This circuit is very simple too. You will notice that there is no current sensing resistor. But it is really there, in a form of the Rds-on resistance of the N-channel FET, which actually handles the load cutoff from the source. The function of the FET is shown in the diagram 2. When the current Id is rising, the tension Uds over the resistance Rds rises very slowly in the beginning, but very fast after the knick.

This means, that before the knick the FET behaves as a resistor but after it, works as constant current source.

The D2, R3 and B-E connection of the Q4 will sense the Uds voltage of the FET1. When the voltage rises enough, the Q4 will shortcut the FET1 gate to mass, and cut the current flow through the FET 1 off.

However, to enable the FET1 to open, there is certain gate voltage necessary, which in this case is brought up by the voltage divider consisting of R8, Z1, P1 and R9. So the maximum Gate voltage will be the one of the Z1, and the minimal will be around 3V6.

The Z1 voltage (Uz1) will thus determine the max current flowing through the FET 1.

The diagram 2 will show that for 5 Amps the Uz1 should be 5V6, and for 20Amps around 9V6.

The Capacitor C4 will determine the “velocity” or the reaction time of the limiter. 100 uF will make the reaction time to be around 100ms, and 1n will make it 1us.

Within the designed limits, the P1 will limit the current output in the range of 15mA to 20A.

You can use both output simultaneously, but the total output current will be limited by the value of the RL. This PSU can be built also for higher outputs, as long as the transformer will handle the current requirements, and you provide sufficient cooling for the Q3.

AM Transmitter

2009-03-11T15:15:00.005+07:00

Download this schematic diagram.

Datasheet semiconductor component. (PDF Format)

1. BC109C

This ircuit is deliberately limited in power output but will provide amplitude modulation (AM) of voice over the medium wave band.
The circuit is in two halfs, an audio amplifier and an RF oscillator. The oscillator is built around Q1 and associated components. The tank circuit L1 and VC1 is tunable from about 500kHz to 1600KHz. These components can be used from an old MW radio, if available. Q1 needs regenerative feedback to oscillate and this is achieved by connecting the base and collector of Q1 to opposite ends of the tank circuit. The 1nF capacitor C7, couples signals from the base to the top of L1, and C2, 100pF ensures that the oscillation is passed from collector, to the emitter, and via the internal base emitter resistance of the transistor, back to the base again. Resistor R2 has an important role in this circuit. It ensures that the oscillation will not be shunted to ground via the very low internal emitter resistance, r_e of Q1, and also increases the input impedance so that the modulation signal will not be shunted. Oscillation frequency is adjusted with VC1.

Q2 is wired as a common emitter amplifier, C5 decoupling the emitter resistor and realising full gain of this stage. The microphone is an electret condenser mic and the amount of AM modulation is adjusted with the 4.7k preset resistor P1. An antenna is not needed, but 30cm of wire may be used at the collector to increase transmitter range.

35W RMS x 3-Channel Power Amplifier System.

2009-03-10T11:12:00.003+07:00

Design Objectives This design is intended to drive the rear (stereo) and center channel speakers for surround-sound applications. This project combined with the 60W+60W power amplifier, which will drive the main stereo (front) speakers, gives a full 5 channel surround sound systems (Total power = 225W RMS). The power supply circuitry, PCB size and dimension should be designed to match nicely with the 60W+60W power amplifier so that later they may be nicely cased togather.

System Operation & Description The LM4781 3-channel audio power amplifier are configured as non-inverting amplifier which has a gain of 20V/V per channel, which is high enough to maintain stability and not too high until increasing the noise and THD+N performance. The inputs are taken from the RCA jacks which then feed to three high quality 1uF metallized polyester capacifor with 63V rating. The outputs are wired to the speaker terminals directly.

The schematic diagram is taken straight out from the National Semiconductor's referance PCB design schematic. However I have omitted the muting switch and replaced it with the soft start circuit, as explaned in the LM4781 datasheet. I have also added the L//R network (L=0.7uH, R=10 ohms 2W) at all the outputs.

For detail all discription, click here.

Radio waves.

2009-03-05T15:47:00.002+07:00

Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed, making practical the use of radio waves to transfer information through space.

Nikola Tesla and Guglielmo Marconi are credited with inventing systems to allow radio waves to be used for communication. for details, click here or visit on wikipedia website

source: wikipedia

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2009-03-05T15:37:00.000+07:00

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300W Subwoofer Power Amplifier

2009-03-05T15:20:00.002+07:00

There are some important updates to this project, as shown below. Recent testing has shown that with the new ON Semi transistors it is possible to obtain a lot more power than previously. The original design was very conservative, and was initially intended to use 2SA1492 and 2SC3856 transistors (rated at 130W) - with 200W (or 230W) devices, some of the original comments and warnings have been amended to suit.

Download this schematic diagram.

Datasheet semiconductor component. (PDF Format)

1. MPSA42
2. MJE15032
3. MJE15033
4. MJL4302A
5. MJL4281A
6. IN4004

170W Audio Power Amplifier

2009-03-05T15:13:00.002+07:00

The combination of the LM4651 driver IC and the LM4652 power MOSFET Class D power amplifier IC provides a high efficiency amplifier solution, suitable for self-powered speakers, subwoofers and quality car boosters.

Download this schematic diagram.

Download datasheet semiconductor component. (PDF Format)

1. LM4651
2. LM4652