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Variable Voltage Regulator – Indermediate


Overview / how it works:

There is a video explaining how this circuit works at this link:


Building the circuit:

The parts list is as follows:

Ω      One LM317 Voltage Regulator

Ω      One LED (any colour!)

Ω      One 270Ω resistor

Ω      One 1KΩ resistor

Ω      One 4.7KΩ potentiometer

Ω      One DC Power Jack

Ω      One 1n4001 diode

Ω      Some strip board

Ω      Solder

The circuit:

LM317 Voltage Regulator Circuit Diagram

Above is the schematic for the circuit, you can see the LM317 Voltage regulator in the middle with the protection diode above it (in reverse polarity, otherwise the output would get a constant voltage from the input). Below it is the voltage divider made up of a 240R resistor to the output, and a 4.7K variable resistor to ground. Varying this resistance varies the voltage the adjust pin (pin 1) on the regulator and so the output voltage. The LED is hooked up with a 1k current limiting resistor across the output, to give a rough indication of the voltage. If you wish to add filtering to it, add some capacitors across the two output pins (10uF should do).

As the layout of this project is very easy on strip board, we will let you do it however you like, however, for reference, here are a few photos of ours:

LM317 Voltage Regulator image

LM317 Voltage Regulator image

LM317 Voltage Regulator image

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