Useful for electronics hobbyists, this linear workbench desktop power supply circuit converts a high input voltage (12V) from the SMPS of a PC into low output voltage (1.25 to 9 volts). An adjustable three-pin voltage regulator chip LM317T (IC1) is used here to provide the required voltages. The LM317T regulator, in TO-220 pack, can handle current of up to 1 amp in practice.

The diagram shows the circuit of the desktop power supply. Regulator IC LM317T is arranged in its standard application. Diode D1 guards against polarity reversal and capacitor C1 is an additional buffer. The green LED (LED1) indicates the status of the power input. Diode D2 prevents the output voltage from rising above the input voltage when a capacitive or inductive load is connected at the output. Similarly, capacitor C3 suppresses any residual ripple.

Connect a standard digital voltmeter in parallel with the output leads to accurately set the desired voltage with the help of variable resistor VR1. You can also use your digital multimeter if the digital voltmeter is not available. Switch on S1 and set the required voltage through preset VR1 and read it on the digital voltmeter. Now the power supply is ready for use.

Read more Source:
http://apowersupply.com/desktop-power-supply-circuit-34.html

This be power motor controller 12V circuit. with a signal MCU Control be high class voltage , about 3V. It can motor control turn advance or walk go backwards all right. By use power mosfet number IRF150 use apply to 100W small stump size hills. The relay 12V 2 contract , for change electronic pole gives motor. By feed a signal Reverse Rotation change a B pins of 2N3904 give it works to give the electric current to the coil relay. This circuit uses voltage 12V at current about 10A. The C1-4700uF help increase efficiency of the circuit while , feed the fire gives motor during first. The D2 use protect the electric current pulls sharply from motor harm with mosfet Q1-IRF150 get. Other detail in the circuit.

This AC to DC converter circuit is capable to convert an alternative voltage from 70 – 260 Vac into a DC voltage from 180 to 250 Vdc.
To achieve this convertion we use a rectifier MC34161 as a voltage doubler at low input voltages and as a classic rectifier at high input voltages.
MC34161 includes a reference power supply which delivers 2.54V at pin 1. The signal level applied at pin 2 is internally compared with a 1.27V voltage.
D5 zener diode, togheter with R1 and C4 provide IC’s required 12V voltage. Capacitor’s voltage of C2 and C3 must be > 250V. [...]
Read more Source:
http://apowersupply.com/ac-dc-converter-circuit-263.html

Here is a simple and effective circuit for driving florescent lamps from a 12 V supply.The circuit is nothing but consists of an oscillator, a MOSFET switch and a step-up transformer for driving the florescent lamp.

The IC1 TLC 555 is wired as an astable multivibrator for producing the necessary oscillations.The MOSFET Q1 is used to amplify the oscillations produced by the IC1.The out put of MOSFET is connected to the primary of the step up transformer to produce a ~400 V AC for driving the florescent lamp.

Read more :http://www.circuitstoday.com/12-v-florescent-lamp-driver-circuit
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This is circuit Automatic Charger and Full charged indicator. For 24V batteries it can charger with current be stable about 1.5A and have voltage output 27Volt with integrated number circuit LM317K. When the battery has had full already , as a result will cut the work. There is a tube LED show the work with use integrated number circuit LT431 perform check the level , voltage battery and systematically protect short circuit with IC LM317. Unless D2 perform protect wasp a pole battery wrong as well. The IC1 should hold heat sink with. The detail is other , see in the circuit.

This is a simple, but very useful circuit that can be used to transmit telephone conversations. When the telephone receiver is on hook the voltage across the lines will be about 48 volts. The preset R7 is so adjusted to obtain a 24.7 V across between the cathode of D2 and ground. At this voltage the Zener diode D2 will be in breakdown and the transistor T1 will conduct. This makes the transistor T2 OFF. When the receiver is off hook, the line voltage drops to about 11 volts. This makes the transistor T1 OFF and subsequently the T2 ON. The T2 in switched ON condition will provide a DC path for the transistor T3 used in the FM transmitter section. [...]

Read more: http://www.circuitstoday.com/telephone-transmitter
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This circuit is DC converter low voltage , 12V from be 1.25V to 10Vdc by can give current topmost get about 1.5A. You should use IC number LM317K because have electric many power more the number LM317T. By should hold heat sink. That have large-sized with. The R4 use for fine decorate voltage output. The C1,C3 , and , C2 , for decrease all noise well. The detail is other , see in the circuit.
circuit source by joe (aircraftdesigner)

Here is the schematic of a simple flouroscent lamp driver circuit based on two transistors.The circuit uses capacitive ballasting for driving the tube.An 8 W standard flouroscent tube can be efficiently driven using the circuit.

The two transistors (2Sc 1983) with associated components forms a oscillator around 1KHz.The oscillator is wired so that saturation condition of the transistors are prohibited.This adds on to the efficiency of the circuit.The circuit produces a clean sine wave with very less noise.

Read more: http://www.circuitstoday.com/8w-flouroscent-lamp-driver
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This be subwoofer filter low pass frequency circuit, for filter especial low frequency has passed by still the amplifier microphone. By this circuit uses op-amp IC number LF347 , perform the circuit filters low frequency change well, It make the sound that go out to have only low frequency ,about 100HZ not exceed. By have Switch choose frequency level that can want as well. This circuit should choose high-quality equipment, because decrease the noise. The detail is other , see in the circuit.

This be mini size power amplifier 2 watt OTL that use IC LM380. Be base readymade circuit for side sound work and the communication. Which use outside equipment adds least. The C6 can choose get many the value since 47uF to at 470uF which , have a voice good bass. The C3 use for decrease tall frequency or noise. It be valuable stay between 0.0047uF sections arrive at 0.047uF. The power supply use 12V sizes from , car battery or the other. The detail is other , see in the circuit.