Hi friends, today we will see how to make a constant current source using a LM317 regulator and a single DC supply. You can vary the magnitude of current using the formula given below.
Circuit diagram
Following figure shows the circuit diagram of constant current generator mini project.
Components required
- LM317 voltage regulator
- 12V DC power supply (9V can also be used)
- Resistor (depends on your requirement)
Working principle of constant current source circuit
As shown in the figure, constant current source producess a 20mA current across its output. The voltage across output is lower than DC supply voltage by 3V. In this case we have used 12V DC supply therefore we will get 20mA current with 9V across its output. If you use 9V DC supply you will get 6V across its output terminals.
LM317 is a linear voltage regulator IC having following specifications:
| Attribute | Value |
| Vout range | 1.25 V – 37 V |
| Operation ambient temperature | 0 °C – 125 °C |
| Vin – Vout difference | 3 V – 40 V |
| Minimum Load Current | 3.5 mA typical, 12 mA maximum |
| Output Imax | 1.5 A (with proper heat sinking) |
LM317 can be used as a current regulator by replacing its low side resistor of the divider with the load itself. In our case, suppose we are using DC motor as load. We will get 20mA current flowing through DC motor. The formula for output current is given by,
I = Vref / R = 1.25 /62 = 20mA
1.25V is the reference voltage of LM317 regulator.
You can download LM317 datasheets from the following links:
- LM317 Texas Instruments
- LM317 ON Semiconductor
- LM317 STMicroelectronics
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The post How to Make a Constant Current Source using LM317 appeared first on MyClassBook.