Simple Lamp Dimmer/ Fan Regulator Circuit

admin November 3, 2018 34 Comments

Lamp Dimmer/Fan Regulator Circuit

We have modified this circuit: - Take a look - Modified Lamp Dimmer 


The light dimmer circuit or fan regulator circuit (either case, the circuit and design are the same, only difference is the output load to be varied, that is, fan or light) is used to control the brightness of the light or the speed of the fan according to our desire. The objective of the circuit is to vary in intensity the brightness of the light bulb or fan speed by using a fixed source. There is no need to replace the bulb with a higher wattage one to do so. A simple Triac can do the work for you. Triacs are used in this circuit as a dimmer as they are easy to design and control, and are very much economic due to their high efficiency and low buying costs.

This is the circuit diagram of the simplest lamp dimmer or fan regulator. The circuit is based on the principle of power control using a Triac. The circuit works by varying the firing angle of the Triac . Resistors R1, R2 and capacitor C2 are associated with this. The firing angle can be varied by varying the value of any of these components. Here R1 is selected as the variable element. By varying the value of R1 the firing angle of Triac changes (in simple words, how much time should Triac conduct) changes. This directly varies the load power, since load is driven by Triac. The firing pulses are given to the gate of Triac T1 using Diac D1.


You will get a better understanding  of the light dimmer circuit by learning more about Triac. Check the links below to know more:-

Triac - Operation & Construction

Triac - Characteristics


Assemble the circuit on a good quality PCB or common board. The load whether lamp, fan or any thing should be less than 200 Watts. To connect higher loads replace the Triac BT 136 with a higher Watt capacity Triac. All parts of the circuit are active with potential shock hazard.So be careful.

I advice to test the circuit with a low voltage supply (say 12V or 24V AC) and a small load (a same volt bulb), before connecting the circuit to mains.

Parts List

R1 1o K 1 Watt Resistor

R2 1o0 K Potentiometer (Variable Resistance)

C1 0.1 uF (500V or above ) Polyester Capacitor

T1 BT 136 Triac

D1 DB2 Diac

Fan Regulator Circuit Diagram

Fan speed regulator circuit and lamp or light dimmer circuit

BT 136Triac Necessary Data.

BT 136 Data sheet,Pin out diagram and specifications

BT 136 Specifications


The light dimmer circuit explained above has been modified with the addition of a snubber circuit to improve the performance of the Triac. A fuse is also added to the circuit.

Check it out here : Modified Lamp Dimmer

We have more Power Control circuits in our website that may interest you:

1. Temperature Controlled Fan Regulator

2. Simple DC Power Delay Circuit

3. Temperature Controlled DC Fan

4. PWM Motor Speed Control

5. Fuse With Status Indicator

  • August 16, 2018

    I have the simple circuit for electrical fan regulator by resistance

  • purnachandrasekhar
    July 30, 2015

    what is the estimated cost of single phase ac voltage regulator using diac and triac?

  • pathik
    April 21, 2015

    how to connect variable resistance (potentiometer)?????

  • nalaka
    March 15, 2015

    dera sir ,
    i have use BT 136 for operate 10uf 400v capacitor but after five time tric if burned , pl give solution

  • Atish Palan
    May 8, 2014

    May i get the relevant waveforms for the firing angle of 60 degrees? please….

  • stebza
    February 24, 2014

    Is it possible to turn this to be automatic light dimmer, for example,substituting that potentiometer with LDR?

  • soham
    December 22, 2013

    and why we use particular component like resister,capacitor value is there are formula for that

  • soham
    December 22, 2013

    sir please can u send me the total documentation of the temperature controlled fan using triac thermistor. Please send me totally as early as posiible

  • PUJA
    September 14, 2013

    How this circuit will be interfaced with PIC16F877?

  • Puja
    September 14, 2013

    Can you please give me the information about how this circuit will be interfaced with PIC16F877?

  • kamlesh
    February 4, 2013

    please give me a circuit that can very 0 volt to 230 volt with 7amp

  • kamlesh
    February 4, 2013

    circuit is good

  • Rishabh V Pandey
    December 27, 2012

    It helped me alot in my project.

  • Rakesh
    May 29, 2012

    It really works so good!! Thanks!!

  • ghadir
    December 10, 2011

    please give me a common circuite control fire thyristors 3phase
    in put 3phase 50HZ 380VAC
    out put 0 – 550VDC

  • Naren
    October 8, 2011

    I want to adapt this design for a 3 phase motor blower. Let me know how I can do this…

  • eng. mohamed
    August 10, 2011

    please help me to control the speed of AC 220v motor 1HP, can i use this circuit with just changing the triac with higher one?

  • July 28, 2011

    Hello sir please can u send me the total documentation of the temperature controlled fan using triac, diac, thermistor. Please send me totally as early as posiible. I will be waiting for your reply.

  • anindya
    May 4, 2011

    we are yet to try it.. hope it works !

  • Seetharaman
    December 8, 2010

    Hi Nohammed Saad The same circuit can be used if it is mains operated LED appeared on Circuits today. If it is DC operated then you can use a variable current source using LM317 or MOSFET.

  • nohammed saad
    December 8, 2010

    i would like to control a dc load like LED s what do you recommend for me??

  • Seetharaman
    December 4, 2010

    Hi Tomin Thank you very much good useful circuit

  • December 2, 2010

    This circuit diagram is very popular and useful. But I have another one with An optional 7-segment display with its associated circuitry has been provided to display your choice of fan speed.

  • ppadhma
    January 22, 2010

    i want to design light dimmer circuit.lamp brightness will be controlled based on already existing brightness in room.give information about sensor i have to use.

  • […] a laser printer-Printed Circuit Boards (8)Simple Water Level Indicator. (7)Digital Stop Watch (7)Simple Lamp Dimmer/ Fan Regulator (7)Simple 40W inverter (7)100 Watt sub woofer amplifier. (7)Dew sensitive switch (7)PWM motor […]

  • Awadhesh Kumar
    August 20, 2009

    I m a 4th year student of EEE department and i m looking 4 project based on automatic temperature controlled circuit. So i choose automatic temperature controlled fan regulator. I need of details about this circuit………..

  • faruk
    July 5, 2009

    how to modify this “simple lamp dimmer/ fan regulator” circuit to dark controlled on off switch by using LDR

  • June 9, 2009

    can any one provide efficient circuit diagram for dc fan regulator at 12v,5A .if so give me some website address

  • RAJ
    April 22, 2009

    May i use any other number in the place of BT136?

  • Arie
    March 5, 2009

    This is sure way to have noise on your power lines in your home it will work but coils filtering make a real world circuit


  • January 14, 2009

    i would like to make a scr controled dc regulated power supply,can u help me

  • pabitra mukherjee
    July 9, 2008

    I would like to connect higher load like 3000watt filament lamp,pls. recommend me the appropriate triac with proper circuit to avoid potential shock hazards.

    • Maneesh
      July 18, 2015

      tell me how many watts of bulb are used in this circuit and were should we have to connect the bulb

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