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How to Build a 120 Volt AC Power Supply for 3 Volt DC Output

Author: ZYG Power Module Time: 2023-4-20

If you looking to power a small device that requires 3 volts of DC power, you may be wondering how to build a suitable power supply. One option is to build your own 120 volt AC power supply and use a voltage regulator to step down the voltage to 3 volts. Here how to do it:

Materials:

– Step-down transformer (120V AC to 12V AC)

– Bridge rectifier

– Capacitor

– Voltage regulator (LM317)

– Heat sink

– Resistors

– Potentiometer

– LED

– 3 volt DC load

– Soldering iron and solder

– Multimeter

Step 1: Choose a transformer

The first step is to choose a step-down transformer that converts the 120V AC input to 12V AC output. Make sure the transformer is rated for the amount of power you need (in watts) and that it has the correct output voltage.

Step 2: Rectify the AC voltage

Next, you need to rectify the AC voltage using a bridge rectifier. This will convert the AC voltage to a pulsating DC voltage.

Step 3: Smooth out the DC voltage

To smooth out the pulsating DC voltage, you need to connect a capacitor across the rectified output. This will help to stabilize the voltage and reduce ripple.

Step 4: Regulate the voltage

Now it time to regulate the voltage to a steady 3 volts using an LM317 voltage regulator. This can be achieved by connecting a resistor and a potentiometer to the voltage regulator, which will allow you to adjust the output voltage to 3 volts.

 

 

 

Step 5: Add a heat sink

The LM317 voltage regulator can get quite hot, so it important to add a heat sink to dissipate the heat. You can attach the heat sink to the voltage regulator using thermal paste or adhesive.

Step 6: Test the circuit

Before connecting your load, it important to test the circuit using a multimeter to ensure that the output voltage is stable and accurate. Adjust the potentiometer until the output voltage is exactly 3 volts.

Step 7: Connect the load

Finally, you can connect your 3 volt DC load to the output of the voltage regulator. You may also want to add an LED to indicate when the circuit is powered on.

By following these steps, you can build a 120 volt AC power supply that provides a stable 3 volt DC output for your small devices. Make sure to follow safety guidelines when working with high voltage circuits, and always test your circuit before connecting your load.

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