Temperature controlled fan regulator

john December 9, 2018 34 Comments

How cool will it be to have an intelligent ceiling fan that will auto-adjust its speed to your comfort!

That’s what we are trying to achieve here.

Fans help to reduce room temperature by circulating air. This circulation mixes hot and cool air in the room, and in effect reduces the temperature to an average value of the hot and cool air temperatures.

As you know, we need some input to control the speed of the fan. Here temperature is considered as a measure of comfort, the less the temperature the more the comfort is.

Here two thermistors are used to measure the room temperature. This change is reflected on the fan speed by regulating the current to the fan’s motor.

This fan regulator circuit will automatically control the speed of your fan according to the temperature. Two thermistors (R1 and R2) are used to sense the temperature. The circuit works almost like the published here previously.

Here the potentiometer is replaced by the thermistors. When the temperature is increasing the resistance of NTC thermistor ( R1) decreases and at the same time the resistance of PTC thermistor (R2) increases. At the same time, the rate of change of the resistance will be different for R1 and R2. This action is similar to a potentiometer used in a conventional Triac based fan regulator. When the resistance is varied the firing angle of the triac changes and so do the speed of the fan.

As a result, the speed of the ceiling fan increases with an increase in temperature and vice versa.

Circuit diagram













  • The circuit can be assembled on a Vero board.
  • L1 can be a 70uH inductor.
  • C1 and C2 must be rated at least 200V.
  • C3 must be rated at least 600V.
  • Triac BT136 can safely handle up to 4A load current.
  • The two thermistors must be mounted as close as possible.
  • sanjeev
    March 16, 2016

    anyone plz tell me whether using 5k PTC is necessary? can i use NTC instead of 5k PTC?

  • siddhu
    March 12, 2015

    i didn’t find 100k ptc,5k ptc where are they available and does the circuit work for 220v or any modification is needed

  • Ali
    March 14, 2014

    I didn’t find diac db2 is it possible to use other part (an alternative) and what is it ??

    • pankaj
      September 9, 2014

      we can use db3 instead of db2 .
      it will work

    March 14, 2014

    I’m looking for diac db2 but I didn’t find itIs it possible to use an alternative and what is it..

    • raag nilim
      June 14, 2014

      db3,db4 etc. Can be used or a mein bulb will work good

  • marco
    March 12, 2014

    May I know what is the use of C2 capacitor and the inductor? Thanks!

    September 30, 2013

    could you please give the circuit of ceiling fan voltage regulator that used in our home appliances.our suppy is 230v,50hz.we will be very benifited and thankful to you if yo do this help.

    September 20, 2013

    Why this type regulator not use in market.

  • thomas george
    February 3, 2013

    what is the use of the l1 and c3?
    and in some websites it says db2 is schottky diode…
    and how much the NTC and PTC cost in india?

  • ABHI
    September 27, 2012

    how to make it for 230v, 50hz, ac supply? also give its circuit digram

    • Namle
      June 13, 2014

      Dear CT,
      I think that your circuit is very usefull, but in my area electric supply is 220V-50Hz, so what part I shoud change in the circuit? Pls inform me more data.

      Thanks in advance.

  • waqar
    May 19, 2012

    What modification required for 220V AC fan motor?

  • December 13, 2011

    can anyone help me,what are the modifications that are needed to run a 230v,1.2A single phase motor.

  • seetharaman
    December 1, 2011

    Hi Akshay the fan should be rated for 110volt 60Hz.
    Hi Zunair and kumar this is a simple speed regulator for the fan. The sensing thermisters should be in the air flow path to sense the air temperature. If the room is already quite hot the fan will be always running at high speed. if the temperature of the room reduces then the speed of the fan will reduce.

  • November 30, 2011

    i have joined the circuit but the fan is working slow why?in the sheet there is no description of the voltages of fan

  • zunair sahhid
    October 14, 2011

    please can some one describe whole of this circuit .em quite new to these things so i cant really get that which bit is doing what…can some one help me out please.
    zunair shahid

  • kumar
    May 30, 2011

    I have tried this circuit,I observed effect of with 10W lamp. It dims when we put cold object over thermistor and brightens when we remove it.But when i connect it to fan the change in speed effect is not much observable.I measured the resistance of thermistor in morning and at high ambient temp. it varies by 26K ohm to 65 K ohm. But it is found that fan kept on for overnight and due to self heating property of thermistor the fan speed remain high throughout.

  • diego
    May 11, 2011

    hola puedo cambiar los valores de los termistores por valores de 1k y colocar un potenciómetro de 150 k en vez de la resistencia de 6.8k. como se comportaria el circuito. no venden los termistores de los valores del plano. gracias

  • diego
    May 11, 2011

    buenas tardes en cali colombia se consiguen termistores máximo de 1000 ohmios ptc o ntc. pregunto si coloco un resistor variable de 150 kiloohmios en vez de la resistencia de 6.8 K puedo obtener un función similar? cual es su consejo. gracias.

  • Seetharaman
    March 10, 2011

    IHi Swapni lt is only a line noise filter it can be left as it is. Increase R3 to 22K or more till you get the min imum required speed.

  • swapnil
    March 9, 2011

    thnx Seetharaman
    should we modify inductor value for 230v ckt

  • Seetharaman
    March 8, 2011

    hi swapnil PTC is a positive temperature coefficient component. NTC is negative temperature coefficient component. PTC The resistance will increase as the temperature increases. NTC is vice versa. You need not carry out any modification to the fan, in the place of existing regulator you can use the above circuit.

  • swapnil
    March 7, 2011

    for what does PTC and NTC stands for?
    and can we connect our fan directly without altering its wndg connection and capacitor

    October 21, 2010

    diuble all the values given for resisters and c3 capasitor u will get the circut for 230v regulator

  • sameer
    September 3, 2010

    what modifications are required for a 230v motor.,??., please reply ASAP.,
    thanks in advance.

  • Aasiya khan
    August 6, 2010

    Is it an embeded system.any software needed?if want 2 b make this project in embeded system what software l b needed???

  • madhavan
    April 10, 2010

    The circuit works well for a 110V fan can you please advice me What modification wii be required for 230V AC fan motor

    • david ochoa
      December 31, 2013

      It’s the same I think, one for each phase.
      210 V to 254 V are actually two wire with two phases an inverse wave and are 105 to 127v (if this is mono-phasic, tri-phasic would be otherwise).
      Maybe you can install two circuits immediately after thermistors, one for each phase.
      There must be another more simple, but that it occurs quickly.

  • sethu madhavan
    March 8, 2010

    What modification required for 230V AC fan motor

  • john
    January 9, 2010


    I did try this circuit, but seems there is some problem in it. I double checked if all the parts are working…I don’t get any voltage variation in the output voltage.

    Can you please halp me with this circuit.

    Thanks in advance

  • amit
    October 25, 2009

    what is the rating of the motor???

  • Iftikhar Ahmad
    July 25, 2009

    What modification required for 230V AC fan motor

      February 4, 2013

      what modification have to be done to reduce 110 v power to a less value to make a mini model of this circuit

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