Intro: Wiring an Adjustable Voltage Regulator
In this simple tutorial I'm going to show how to wire a voltage regulator with a potentiometer to adjust the output voltage. I'm using an LM317T which is readily available and versatile. This Instructable is mostly for the novice, I've tried to cover every detail but is probably overkill for anyone with prior electrical wiring experience.
Step 1: Parts List
- voltage regulator (LM317T shown)
- schottky diode
- 240 Ω resistor (more about the value of this later)
- 0.1 µF capacitor
- 10 µF electrolytic capacitor
- 1 kΩ potentiometer
Step 2: Step by Step Wiring
- This is literally step by step, so there is probably a lot of redundancy, I wanted to make instructions that even a complete novice could follow. Each frame is numbered in the left hand corner and will coincide with each numbered step.
- Step 1. This circuit doesn't take up a lot of space, maybe a square inch or less. placement on your perfboard is something to consider if you plan on wiring anything else to your circuit, and with a voltage regulator you probably will. Also if your voltage demands are high be sure to leave enough room to add a heat sink, these get hot depending on their use. I started in the corner but place it anywhere you'd like.Cut a piece of red wire and strip the ends and insert it into a hole on the perfboard and solder in place.
- Step 2. Bend the wires of the schottky diode down to resemble a "staple" shape. Diodes are directional, meaning electricity will only flow in one direction through them. This is indicated by the silver band, I think of it a barrel with the band being the open end. Like, you can only fill the barrel from the open end. The band should be placed so the electric supply feed to that end first. Place your diode on the perfboard and solder to the wire already in place.
- Step 3. insert the voltage regulator next to the other end of the diode. Voltage regulators are also directional with three pins labeled adjust, out, and in, in that order if your looking at the front of it. The "in" pin should be wired to the diode.
- Step 4. Next the 0.1 µF capacitor is inserted. This can be inserted in any direction. This is soldered to the "in" pin as well.
- Step 5. Bend the resistor like what was done with the diode, in the photo I bent mine into a "v" shape to conserve space. Attach one of each end to the two open pins on the regulator, one end to out the other end to the adjust pin.
- Step 6. insert the electrolytic capacitor. One end will go to the out pin the other will go to ground. This type of capacitor is directional. The side with the white strip on it is negative, this end will go to ground. Solder the other wire to the out or middle pin.
- Step 8. Cut and strip the end of another piece of red wire, this will connect to the positive wire of the electrolytic capacitor. This wire will be the connection to the positive or supply wire to your device.
- Step 9. Insert the potentiometer into the perfboard, orient it so that the middle connection is the closest connection to the adjust pin on the regulator. Bend the regulator toward this connection and solder them together.
Step 6: Combining Ground Connections
- Step 10. Cut a length of solid core wire long enough to join one of the unconnected potentiometer wires to the remaining wires of both the capacitors. connect the remaining potentiometer wire to the one you just soldered the solid wire to.
- Step 11.Solder the other end of the solid core wire to the ground wires of the two capacitors.
- Step 12. Cut two more black wires, strip them, and insert them next to the ground wires. Solder these wires to the ground wires as well. One of these will go to supply ground the other will attach to whatever device your trying to regulate voltage for.
- The red wire in the corner will be from your power supply
- the other red wire will be to supply power to whatever your supplying voltage to
- either of the two black wires can go to your device ground
- the other black wire will go to supply ground
- the value of the resistor can be changed to suit your purpose as can the value of the potentiometer giving you more higher voltage or to get more precise control of the voltage, or the potentiometer can be changed to a resistor that has a value that will give you the voltage you need, it just wont be adjustable.