A simple adjustable power supply is an electronic device capable of converting a source(either AC/DC) from one voltage level to another. They fulfill a wide array of requirements in industrial as well as academic settings such as test bench supplies and load matching applications for variable DC drives. By Definition, an AC/DC power supply takes in an AC/DC Signal (depending upon the configuration) & shifts it to the desired voltage level. So, in today’s tutorial, we are going to design a simple Adjustable Power Supply Using LM317 Voltage Regulator IC.
The heart of this power supply is an LM317 voltage regulator IC. LM317T is a three-terminal voltage regulator IC, with a high output current value of 1.5A. The LM317 IC has many features such as current limiting, thermal protection, and safe operating area protection. It can also provide a float function for high voltage uses. If we disconnect the adjustable terminal still, LM317T will be helpful in overload protection.
Hardware Required
You will need the following parts to build this project:
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Voltage Regulator IC | LM317T | 1 |
| 2. | AC Adapter | 220V AC/12V DC | 1 |
| 3. | Digital LED Voltmeter | – | 1 |
| 4. | Resistor | 1K | 1 |
| 5. | ON/OFF switch | – | 1 |
| 6. | Heatsink | – | 1 |
| 7. | DC Power Jack | Female/3.5mm | 1 |
| 8. | Potentiometer | 10KOhm | 1 |
| 9. | Soldering Iron | 45W – 65W | 1 |
| 10. | Soldering Wire with Flux | – | 1 |
| 11. | Jumper Wires | – | As per need |
| 12. | AC Wall Outlet | 220V | 1 |
| 13. | Alligator Clips | – | 2 |
LM317 Pinout
Useful Steps
1) Screw on the voltage regulator IC on the heat sink (optional).
2) Solder a 10K resistor between the Vout & ADJ terminal of the LM317 regulator IC.
3) Solder the +ve terminal of the DC power jack to the Vin terminal of the LM317 IC. After that, Sodler the -ve terminal of the DC power to the fied end/GND of the 10K pot.
4) After that, solder the wiper terminal of the 10K pot with ADJ pin of the LM317 IC.
5) Solder the signal/shunt of the digital voltmeter with the Vout pin of the LM317 IC. After that, Solder the Vcc & GND terminals of the voltmeter with the circuits’ Vcc & the GND/fixed end of the 10K pot respectively.
6) Power up & Test the circuit.
Working Explanation
The working of this circuit is very simple. A 220V AC wall adapter is used to translate the 220V input AC to a Rectified 24V – 12V DC signal, which is then fed to the Vin terminal of the LM317 using a DC power jack. This three-terminal voltage regulator has an output voltage operating range from 1.2V to 37V DC with a maximum load current of up to 1.5A. You can tune the output of the regulator IC by connecting a 10K pot between the Vout & ADJ terminal of the IC.
The LM317 IC output is then connected to the signal probe of a voltmeter to display the immediate voltage across any load such as an LED or a DC fan etc.
Applications
- Adjustable Power supplies serve in applications such as powering home appliances, power tools, test bench supplies & trainer board supplies.
- Commonly used in testing small electronic projects.
