Voltage Regulator

A linear voltage regulator is used to regulate an input voltage to an output voltage. For an exhibition setup, I wanted to power four 7 V lamps from a 12 V power source. Switching power supplies are normally available for nominal voltages. However, since 7V deviates from these standards and I only had one day for possible troubleshooting, I had to come up with a quick and easy solution. I therefore decided to design a linear voltage regulator.

Testing the circuit

Circuit Design

Unlike conventional power supplies, the linear regulator converts excess energy into heat. So when our light draws 1A of current, the remaining 5V (12-7) – which result in 5W – will be converted to heat. This type of regulator is therefore not suitable for frequently manufactured and used products. However, for quick, one-time solutions, it is very simple and straightforward.

Circuit schematics

Now let’s take a look at the circuit. At the heart of it is an LM317. This is the actual voltage regulator. We connect the Adjust PIN to a trimmer (TRIM) and the trimmer to ground. We will also connect the trimmers wiper to ground. With a trimmer the voltage can be adjusted much more precise than with a rotary potentiometer. We also connect the Out PIN to the trimmer via a 240Ω resistor (R1). To smooth out fluctuations we add two capacitors (C1, C2) to the input and output.

PCB

After testing the circuit on a breadboard, I designed a PCB and sent it to productiown. The resulting circuit board is about 2x4cm. The voltage can be adjusted by turning the adjusting screw on the trimmer. If the LM317 generates a lot of heat, it can be mounted upright and a heat sink can be added.

Manufactured PCB

Ready for use!

Credits

The component was made possible by the help of Peter Knobloch and Elias Mack.