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  • This triac-based 220V AC motor speed controller circuit is designed for controlling the speed of small household motors like drill machines. The speed of the motor can be controlled by changing the setting of P1. The setting of P1 determines the phase of the trigger pulse that fires the triac. The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded.

    220VAC Motor Speed Controller Schematic

    dc motor speed controller schematic

    For example, when the motor of the drill machine is slowed down by the resistance of the drilled object, the counter-EMF of the motor also decreases. This results to a voltage increase in R2-P1 and C3 causing the triac to be triggered earlier and the speed increases accordingly.

    Printed circuit board layout of the motor speed controller
    motor speed controller pcb

    Another version found here.

    motor speed control

    If the main use for this circuit is to control the brightness of a light bulb, RS and CS are not necessary.

    ask a question

    71 Responses to "AC Motor Speed Controller Circuit"

    1. actually, i was looking for 4 1/2 digitanlog multipurpose panel meter & obstacle avoidance robot using vb programming having image capturig facility

    2. wow, really cool! And its quite simple as well!

      I need someone to answer this question though: Will the circuit operate on 110-120 Volts AC? I don’t have 220.

    3. ic tda 785 is the best solution for motor control.

    4. the circuit is great and promising but what type of capacitors and voltage did you use un this circuit? What are the wattage of the resistors too?

    5. ameer ahmed says: on July 8, 2010 at 10:23 am

      it is very use full can we use this to regulate the heat of electric heater or controll heavy watts equiptments .

    6. hii, can u give me about the info on cellphone based motor speed controller….. can u mail me on sekharsushma638@gmail.com… plz

    7. Jacques Fourie says: on March 6, 2011 at 6:33 pm

      Hi, is T1 and T2 the same component? If so where does the third leg go on T2(diag), how should i soulder the transistor?
      If not what is T2?

      • Wibowo N. says: on August 16, 2011 at 7:40 am

        The active devices T1 and T2 are not transistors. T1 is a TRIAC more appr. an alternating current switch and T2 is a diag
        it looks like a diode and has only 2 terminals it is a something like 2 zener diode in parallel in two direction.

    8. Actually the circuit has errors. The layout of the board does not match the circuit (C1 should not be connected to the gate of the triac according to the diagram). Also, the group R1 – C1 – C2 does not seem to have any role, probably the node C1 – C2 has to be connected somewhere else in the circuit.


    9. can u plz tell me which triac is used there? n can we control the speed of the fan with this circuit?

    10. it’s a cool circuit it worked jst very fine for me

    11. ..what kind of triac and diac is used in this particular circuit?…i need help…thank you

    12. ..what kind of triac and diac is used in this particular circuit?…i need help…

    13. …whats the number of triac and diac that is used in this circuit?…I need reply

    14. I saw a lot of motor speed control schematics but i don’t understand why does it needs the diac ???
      and why the Inductance ?
      I don’t want the motor’s speed to jump from 0 RPM to 40 RPM… what is that diac’s role ?? ?
      Can’t be used without the diac ???

    15. you mentioned DC Motor. It supposed to be AC Motor

      • Thanks a lot, changed it!

      • karthikmula says: on December 17, 2014 at 5:23 pm

        samuel,can u send me the pdf document of ur project,as the design parameters and equations are required for our final project. as your circuit is similar to that of our project”speed control of induction motor”please send the soft copy to my mail”karthikmula@gmail.com”.its very much needed

    16. is this working? and what type of motor/ specific motor should i use? xD

      • This is the classic control for a universal AC motor. Not a DC motor. To run a DC motor, the motor must be wired to the DC output of a bridge rectifier.

    17. Has anyone successfully used this circuit for 120 VAC?
      What component values need to change and to what?

      • For universal (brush type) motor that runs on AC or DC, but this is strictly an AC application.

        For 115VAC, change P1 to 100K and R2 to 33K. L1 could be 100uH, but this component is non-critical to operation as it to prevent RFI to receivers etc.

    18. It looks good! The diac could be a STMicroelectronics DB3TG.

      I might use this circuit in my wife’s vacuum cleaner. Its speed control is drastically varying. The regulator uses a uC chip ST62T00C and a BTB16 600v triac. Nothing looks ‘cooked’ nor o/c nor s/c. The motor runs fines too. I’m about to try a BTB24 (24A) replacement. Maybe that’ll work.

    19. Using the circuit for a 1 amp 100 watt 1/8 HP universal motor I had to reduce C4 to .022uF to get any sensible action. Then I dropped R3 to 33K, scrapped R2 and changed P1 to a value of 150K (well, I put a 470K in parallel with the original 220K var).

      Now I get control from pretty slow to almost full speed.

      I’m using the triac and diac suggested by Samuel above.

    20. need to make 6 speed what modification to circuit

    21. PHIL EDWARDS says: on September 9, 2013 at 6:26 pm

      Hi, can you tell me alittle more about the unductor. ie. the max current it may carry. Do you think RS may stock a suitable component?

    22. Circuit does not match board.
      Which is the correct build way for success ?
      Board OR Circuit ?

    23. What kind op capacitors do I have to use?
      It’s a 230V AC circuit, but what voltage rate
      is the minimum for the capacitors? Will 100V be ok?
      Do I need MKT, MKP or AC-catagory?


      All regards.

    24. add:

      AC-catagory is the folder named “Wissel-Spanning”

      • Not PWM, but a phase controlled TRIAC. Nice package.
        However I can say from my experience that there is no way it can handle 25A continuously–probably contains a 25A TRIAC, but to keep it below the rated junction temperature, the case must be kept below 85°C. With an on-state voltage of 1.2V, P = 30W. This requires a heatsink rated at less than 2°C/W. The best PCB heatsinks (much larger than this one) run at over 3°C/W.

      • Hi,I understand, but I only have a AC-230V 100 Watt motor so thi sparticulary pcb can handle the ‘little’ current.

        The actualy question is about the capaciters types.

      • The snubber /filter capacitors (C1 & C2) should be 600 to 660VAC polypropylene type for 220VAC, but this does not mean that other 400VDC film capacitors will not be reliable. C3 & C4 may be low voltage film (100V).

    25. Oh wait, i see what you say.
      Looking at the picture you can see the diac and some other components. It’s defenitly a phase-cutter but they placed the term PWM in the title.

    26. kitopel vargas says: on January 9, 2014 at 3:24 pm

      what are the values for triac and diac?and what voltage rating for the capacitors and wattage rating for the resistors.thanks.gonna try this for a certain project.

    27. Hi i have made this project but i have a problem,at max speed the motor doesnt even move just buzzing what can cause this problem and please reply how to fix it sooner as posible.Here is the parts i have installed:
      Triac BTA 16-600B ,
      Diac DB3 blue colour,
      resistors 68K 47K 180 ohms,
      potentiometer 220K,
      Inductor 330 microHenrys,
      and capacitors 104J100 they are 100 nanoFarads.
      PS.the motor is from drill and it works perfectly and i have wondering about the inductor because in the project says 220 microHenrys and mine is 330 microHenrys it looks like theese
      i have other inductors but they are very small 6.8micro 4.7micro and 12 microHenrys

    28. the pcb does not match the schematic diagram. in the PCB, C1 should be disconnected from the gate instead connected to R2 and connected to the motor, making R2 and C1 parallel. Also R1 should be connected to L1, C2 and the 220V AC line.

    29. 180 0hm resistor got burned when i connect this to a 250 v 5 amp ac motor….what counld have gone wrong plese give ur rplys as comments immedietly as i have a project to submit…please

      • Many possible causes–C1 shorted, C2 open, incorrect capacitor or resistor value.

        The capacitors should be film type of at least 400V (preferably polypropylene).

        The 180Ω resistor should be 1/2W or greater carbon composition or wirewound so it can support the high transient voltage /current (peak power) that occur in the snubber circuit. My guess is that this is the issue–I know from experience that carbon film generally cannot handle the peak power–very short thermal time constant due to the very thin resistance element.

    30. I built and tried the pcb circuit. The motor run like a newly ridden horse. There were also some sparks in the wire inside the motor. After that the pcb circuit is no longer functioning. But the motor is is still ok when I plugged it directly in the 220 AC line.

    31. can anyone list all the parts u’ve used in detail

    32. BATronics says: on April 1, 2014 at 7:35 am

      This circuit does have misinformation included. There a few other components needed. I have done extensive work on this type of control and do have a fully functional circuit for 220 /240 v single phase . The circuit I have will work for any inductive or resistive load simply by changing the triac. The 2 components T1 &T2 are shown as seperate units,a diac and a triac,they can be replaced by a quadrac, which has the same 3 terminals as the triac. Still, there are the other few components needed that aren’t shown in the diagram, those are for tuning and stability control. My control was originally designed and used for controlling a 240v universal series wound brush type motor, but it will work for resistive heating loads , as there is little difference in how either works. Inductive loads and resistive loads share certain common aspects. The main difference is how inductive loads respond to harmonics generated in the circuit, these come from magnetic properties of the running motor and the switching properties of the circuit. There is a lot of complicated math in this stuff.

      • Thanks for the information! Can you send us your functional circuit?

      • kiwibird says: on July 2, 2014 at 9:26 am

        “Still, there are the other few components needed that aren’t shown in the diagram”
        Hi Batronics, can you give updates circuit? Will this work for swimming pool pump?

    33. BATronics says: on April 1, 2014 at 8:05 am

      There are differences between a 120 v circuit and a 240v circuit. If you understand that these 2 power supplies are actually half or series of the 2. This where some confusion comes from between U.S. and foreign lines. This topic is a widely covered one on the net, none of the circuits listed for what is labeled 230v will work for domestic line! In 120 v you need only use 2 wires,a 3rd ground is for safety. In 240 v you can use also 2 wires, a third wire ,for a grnd.also for safety and a 4th, neutral will split the voltage so that there are 2 voltages of 120 each between one hot and the ntrl. 2 hots gives 240v . This is where the math needs to be done. Simple ohms law tells you that if you raise the voltage, at the same resistance ,the current goes up. Your resistor values must be changed if wish to use one V or the other. The value of the caps. should not vary much for most of the circuit because the purpose of the caps is for filtering the AC and allowing the circuit to supply a gate triggering pulse to fire the mains switch, the triac. The diac’s purpose is to balance the firing of the triac at either polarity. The circuit will work without a diac, but it will have some issues. Using the quadrac will reduce the component count by one and will give you a switch that is very well balanced, that means the load will see the same mirrored phase angle for both cycles.

      • Benjamin Martin says: on July 9, 2014 at 4:41 pm


        I need a controller for a 120V 5amp universal brush motor, can I use this circuit? The motor is from the 1950s and says that is for AC and DC current. could you please send me a diagram of your circuit. I need a set speed of about 10,000 rpm that adjusts when there is a load.

    34. Abdulraheem d'yab says: on April 21, 2014 at 1:25 pm

      I want to make this circuit on treadmill in this parameter
      (750w-5A-230V-AC Motor-3000RPM). Can i make this circuit by this parameter ??

      • Bad idea. For a treadmill, you need speed control. This control cannot regulate speed, especially with an induction motor as it appears. Also, you need a control that can handle overhauling loads like a regenerative drive control–very difficult with AC motors, but relatively simple with DC motors.

    35. Liutauras says: on May 18, 2014 at 12:12 am

      would triac can be (BTA08_ 800V 12A Igt/Ih<70/60mA TO220AB) ???? or (BT139_ 800V 16A Igt/Ih<70/60mA TO220AB) or somethink like that…???

    36. hasta que potencia aguanta?

    37. Benjamin Martin says: on July 9, 2014 at 5:20 pm

      can you explain the difference between PWM controller and SCR controller and this that uses a triac.

    38. this circuit can control motor speed high rpm to slow rpm or not ??for example 1440rpm to 120 ?

    39. murugesan says: on October 6, 2014 at 7:17 pm

      how to vary speed of 3 phase induction motor,without vfd.

    40. Arena Lejyon says: on November 16, 2014 at 9:13 pm

      Can someone share the speed control unit of 3-phase 500w ac motor?

    41. I want to make this circuit for household Motor about 200 watt….can anyone tell me…. What should be the components……will I use

    42. ashraf sayed says: on November 27, 2014 at 12:24 am

      really it is very usefull circuit but needs details i use it in washer machines AC motors.

    43. karthikmula says: on December 17, 2014 at 6:01 pm

      sir i want a dc series motor to speed control.by varying motor output voltage we can vary the output speed.main problem is i should know how you designed the values of resistors and capacitors and potentiometer and inductor values in above circuit?. can we use it for speed control for induction motors

    44. HANSUMFEROZ says: on January 22, 2015 at 9:25 am

      sir i want a control circuit for 1HP,14440 RPM , 10 amps, 240 V single phase induction motor. can i use this circuit as it is ? or what changes will i have to do to make it work for my application? please guide me sir

    45. Hi,
      I want to replace potentiometer/P1 220K with single pole 4-5 step/way rotary switch for my old ceiling fan. Which Diac will match with Triac BTA10 or BTB10.
      Please suggest changes.

    46. It is very useful .how can make it the ac motor rpm controlling circuit do you answer me

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