Monday, 14 January 2019

LED Dimmer Circuit with LM317

Today in this article we will discuss LED Dimmer Circuit or simple adjustable Voltage regular Circuit with LM317. LM317 was first introduced in 1970 from then until now the I.C is used for small Transformer Based Variable Power supply.

Things needed for the Circuit:

  1. 330 Ohm resistor
  2. LM317
  3. One 12v LED as a Load
    (We will use this LED for LED Dimming Observation.)
  4. A 12V Power Supply.

Circuit Diagram:

Watch The Youtube Video:


How Does it work?

This is a simple circuit with LM317. We use a Potentiometer/ Trimmer for varying the voltage of adjusting pin. It is connected in such a way that if the residence of the potentiometer is increased then the LM317 output voltage decreases. And in a similar way if the resistance decreases then the output voltage from LM317 increases.

Note: I have used a 10k linear potentiometer. If you want to get more accurate output then I will suggest you go for multiturn trimmer or potentiometer. It will give you a great experience.

You May Also like our another Article about LED Dimmer with 555 Timer


  1. Is there not a voltage drop across the LM317 ?

  2. should there not be a bpass cap 'before' the LM317 ?

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