Simple DC Motor Speed Controller Circuit

When it comes to controlling motor speeds uniformly and efficiently, a PWM based controller becomes the best option, learn more regarding a simple circuit to implement this operation.
The circuit of this PWM controlled DC motor speed controller may be understood as follows:
Initially when the circuit is powered, the trigger pin is in a logic low position since the capacitor C1 is not charged.

The above conditions initiates the oscillation cycle, making the output change to a logic high.
A high output now forces the capacitor to charge via D2.

On reaching a voltage level that’s 2/3 of the supply, pin #6 which is the threshold of the IC triggers.
The moment pin #6 triggers, pin #3 and pin #7 reverts to logic low.

With pin #3 at low, C1 yet again begins discharging via D1, and when the voltage across C1 falls below the level that’s 1/3 of the supply voltage, pin #3 and pin #7 again become high, causing the cycle to follow and go on repeating.

It is interesting to note that, C1 has two discretely set paths for the process of charging and discharging via the diodes D1, D2 and through the resistance arms set by the pot respectively.

It means the sum of the resistances encountered by C1 while charging and discharging remains the same no matter how the pot is set, therefore the wavelength of the out put pulse always remains the same.

However, since the charging or the discharging time periods depends upon the resistance value encountered in their paths, the pot discretely sets the these time periods as per the its adjustments.

Since the charge and discharge time periods is directly connected with the output duty cycle, it varies according to the adjustment of the pot, giving form to the intended varying PWM pulses at the output.

The average result of the mark/space ratio gives rise to the PWM output which in turn controls the DC speed of the motor.

The PWM pulses are fed to the gate of a mosfet which reacts and controls the connected motor current in response to the setting of the pot.

The current level through the motor decides it speed and thus implements the controlling effect via the pot.
The frequency of the output from the IC may be calculated with the formula:

F = 1.44(VR1*C1)

The mosfet can be selected as per the requirement or the load current.

The diagram of the proposed simple DC motor speed controller circuit can be seen below:

217 Replies to “Simple DC Motor Speed Controller Circuit”

  1. hi Swuag ,could you tell me

    what model of mosfet do you use it
    or what model
    beacause is burned it ,,,down ,,,

  2. Hi Mr Swagatam, I would like to clear my doubts about PWM circuit. The output from the above circuit is used to control a single motor right ? and if I want to control two motors do I need two of such PWM circuits for each motor or can a single PWM circuit as above will be able to control both motors ? Thanks.

  3. Hi Mr Swagatam, just would like to add a couple of notes to this circuit. It works like charm, thanks to you. I found adding a 470uF capacitor across the MOSFET's Drain and Source reduces the buzzing sound when the potentiometer is close to being completely off. I am not sure for those that try this circuit with smaller motors but I tried this pwm circuit to control a automotive power window dc geared motor and it produces this buzzing like sound. Another thing to mention to others that try this circuit is, make sure you add a signal diode like 1N4148 if your motor is small and a rectifier diode like 1N4001 to 1N4007 across the motor terminals in reverse order to prevent EMF discharge from entering the MOSFET when the motor halts abruptly. Thanks again to Mr Swagatam.

    1. Hi Mr JR,

      You are correct! Adding a capacitor arrests the noise at low speeds.
      Though modern mosfets have built-in back emf protection diodes, adding an external diode is always good and your suggestion is worth noting.

      Thanks and Regards.

    1. Yes you can do it, just connect a 7812 voltage regulator stage in between the 24V supply and the IC supply terminals.

      The motor should be connected directly to +24V supply.

  4. Mr. Swagatam,
    Thanks for explaining nicely the working of this circuit and I really like your blog. I am a mechanical engineer by profession and I am not an expert like the people in this forum. I am trying to learn some electronics so that it is helpful for my projects. In fact I am planning to build a circuit on my own for the project I am working now. It would be a great help if you can put a circuit for a 36v DC motor drawing about 30A max.

  5. Hi Swagatam,

    Can you give a circuit for a 36v DC motor drawing a current of 30A max? I am a mech engineer trying to learn electronics and I want to build this circuit myself? Thanks

    1. Thanks a lot Mr Swagatam. That sounds very simple. I have a battery bank made of 12v lead acid batteries, in this case I think I can take a separate connection from 1 battery to power the IC. Am I doing the right thing?

    2. Mr. Swagatam, I am amazed at the speed at which you respond. It shows your passion in this. I really thank you for this great service.
      After reading all the comments, one more query pops up, pardon me for my lack of knowledge in electronics. In my design the maximum current can go up to 30A, this is during starting of the motor from rest or when the motor is loaded. Current during normal running is between 10A to 20A. Now what rating of mosfet should I use?

    3. Thank you very much Ravees!

      You are right, the initial peak current can destroy a 15 amp mosfet, so you may have to select a mosfet capable of handling in excess of 50 amps.

      You can get many examples online, just google 50 amp mosfet, and you would be able find many datasheets of such devices, select any suitable one from the lot, all will work.

    4. Dear Mr. Swagatam,

      I have decided to make the bold step of building this circuit on my own. I need some more input from you.

      I have put the parts list below, can I just go to the market and purchase these items as per the list below? will I get what is needed? or should I change the description/specification/trade name here?
      Also let me know the mosfet that I have chosen as per your advise is the right one for my application.

      1 IC /555 Timer/ 1qty
      2 Diode/1N4148/ 2qty
      3 Capacitor/0.1uF/ 2qty
      4 Capacitor/0.01 uF/1qty
      5 Resistor /10K/1qty
      6 Mosfet/ STP55NF06L (55A, 60V)/ 1qty
      7 Pot/100K/1qty 1

      Next, How do I assemble it on a PCB? Should I get a generic board and solder it with a wire? what is the wire type should I use in that case?Please advise.

      How do I decide on the heat sink for the mosfet? after reading the material on the net I understand that it genereates heat and a heat sink has to be fitted, I saw in the data sheet that Tj(operating junction temperature) is -55to175C, what would you advise?

    5. Hi Ravees,

      The parts list is OK, just put "ceramic disc" with the capacitors so that the dealer does not get confused. The resistor is 1/4 watt rated.

      PCB can be a pieceof general purpose board or a veroboard.

      The parts can be joined by bending their leads itself and soldering them with each other as per the diagram.

      Heatsink may be tried through trial and error,any piece of aluminum that is able to manage and control heat dissipation efficiently is what we need. To begin with you may fit a 5×3 inches/3mm aluminum piece as the heatsink.

    6. Dear Mr. Swagatam,

      Thank you for your input and guidance.I have another query. This week I was in Singapore and happen to see a DIY kit for motor speed controller and bought one though it did not meet my specs. I thought I would learn building circuits with that. In the instruction manual the circuit shown is same as what you had shown, however there were some differences. For example there are 2 resistors( 5K & 30K)across the 500K pot along with the diodes 1N4148. Also there is one more resistor (300 ohms) towards the base of the mosfet/transistor. He calls it transistor (c1061) instead of mosfet . There are 2 other diodes one across the motor and one on the positive 12v line. Are these some kind of a safety features? Please throw some light on this. I wish I could show the circuit here.

    7. Dear Ravees,


      Different individual circuits may have there own specific configurations, will be difficult to say anything without seeing it practically.

      As far as the above circuit is concerned, it's a universally tested design and normally will not require any further refinement because it's very safe.

      In the above circuit one 470uF/25V should be added across the mosfet drain/source for reducing RF generated from rapid switching.

    8. Thank You. Sorry, one more query.I am planning to control the speed of the motor with a throttle grip which I think is a 5K Pot, so If I put a 5K pot in this circuit will it have a problem?

    9. Dear Mr. Swagatam,

      Sorry I am bothering you again. I am trying to control the speed using the throttle grip (electric bike throttle)which is available in the market. Its rating is only 5K. How do I use this? What modifications to the circuit I need to do?

    10. Dear Ravees,

      I think a 5K variable resistor will also work, in fact any value will work, because it's the ratio across the pot which matters and not the resistance value.

      C1 should be made 0.01uF though.

    1. Thanks Swagatam I ask one more question
      Mosfet details & Resistor wattage And Another question

      Emergency light or Inverter battery fast charging circuit (full charge with in 30-60 minute charging)
      Circuit diagram send pls

    2. Hi Thameem,

      you can use the mosfet NTD20N03L27 or any 30V 15 amp type. Resistors are all 1/4 watt

      I am sorry you cannot charge a lead acid battery in 60 minutes, you would require Li-ion batteries for that, but these are yet to be manufactured and produced in the market.

    1. Yes the circuit will work for the specified application, use a IRF540 mosfet, may be you can put a couple of them in parallel that will make the circuit even more reliable.

  6. Thanks for the fast reply! Now I just need to find a high power 90V power supply. They seem to be very expensive. Do you think I can use a resistor to drop the 90V to 12V and then regulate that 12v with the 7812? Calculated I'd need a 7.8k ohm 1W resistor using 10ma current draw from the LM555 I have. Let me know if my figuring is correct. Keep up the great work here. Thanks again.

    1. Oh yes that's crucial, your idea looks good and might work.

      If you are using a resistor for dropping the voltage, you wouldn't need a 7812, a 12V zener diode will do the job instead.

      you can make it 6V rather, your mosfets will be happier.


  7. Well I've been doing a lot of searching for power supplies and ready made supplies are expensive and the cheaper ones don't give me enough amps to run my 90v 15a treadmill motor. Saw an idea to make a step down transformer and a bridge rectifier but must admit the design part of that is beyond my skill. Was thinking of taking an old microwave oven transformer and rewind it to get the proper step down AC voltage and then make a beefy rectifier bridge to power the motor controller/treadmill motor. Any reference material you could steer me to would be much appreciated. Or if you have a better idea for a switching power supply to accomplish my task, that would be helpful. Thanks again for your service to everyone here.

    1. The specs are quite odd, It will need to be custom made. Neither smps nor a transformer would be available ready made with such ratings, it looks difficult. I'll try to look for it, will post it if I find one.

    1. Yes you may do it….make the neutral and all the earth points of the circuit common….connect phase wiht the upper terminal of the motor, connect gate of the triac to the output of the IC via a 1K resistor.

      the center pin of the triac would go the motor lower terminal, left pin to ground, while the right pin would be the gate as discussed above…

  8. HI
    Just been looking at your cct and it shows pin 7 as the mofset control, all the other 555 ccts I have seen the output is pin 3, what is the diference?

    1. Hi, Actually I have taken this circuit from another website where a different option was experimented by using pin#7 as the output….technically both types work quite identically, so you may try the conventional type…theer isn't much difference.

  9. Hallo Swagatam,
    I have built the cct on here and it is working the problem I have is the motor speed is about 0 to 100% over 10% of potensiometer rotation any pointers on how I could rectify this? I did look at some other ccts strange how they vary on the out put pin choice!!
    Yours hopefully

  10. Hallo Swag,
    OK yes I have reduced the pot 25K and again to 5K with no effect sadly. Do the diodes have to be matched I have the two IN4158s in and the cap is a .1 cer disc. I cannot think of any thing else that would cause that inbalance!! I have changed the 555 and thoughly checked the circuit.
    sorry to be a pest! Tried

  11. Hello Swagatam,

    I'm doing the standard stick a 90vdc-treadmill-motor-into-a-BSA-frame-with-five 12volt-15amp/h- batteries. I am currently using your design with one 12volt for the motor and one 9V for the controller. Works well, you did a great job. Now, as I add batteries, my voltage will increase as will my amps. (I am assuming the motor has a 15 amp/h draw, most of them do. I will have to change my MOFSET, I know. But to what? Should I use multiple ones? How to I attach them? I majored in ME and English, not EE. (Regret that now)

    Any help would be stellar.


    1. Hello Chopper Rob,

      You may try mosfet SK1058, it is rated well above the required specs, however the 555 IC should be powered with 9V to 12V supply, and must not exceed that.


  12. Hello Swagatam,

    I'm new to the whole PWM idea, but you seem be the person to talk to. I'm using your design with a 12 volt 15amp/hr motorcycle battery attached to a 90VDC 15 amp treadmill motor. It works great. Now, I want to add four additional batteries to take me up to 60 volts. I know I to change MOSFETs, but to what? Is it to my advantage to add multiple MOSFETs, if so how? Any help would be stellar.


    1. Hello Rob,


      It's simple, select a mosfet whose rating matches your supply input rating, in fact the mosfet rating may be chosen a little higher, so in your case a SK1058 would do the job well.


  13. Hello, I am using a Dayton dc motor rated at hp 1/30, 90v, and .35A. What would be my parts list for this motor speed control, thanks ! Really appreciate it

    1. The same circuit can be used for your application too. Just make sure the IC circuit gets around 12V supply derived from the 90V supply.

      The motor can be connected with the 90V supply directly in the manner shown in the diagram.

    2. and in this circuit, where is the positive supply and where is negative connected ? sorry for all the questions

  14. Lets say I am using a 12 v motor with current x, what kind of power supply should I have? And how should I select a MOSFET ? I have a power supply of 12v and 165mA that I could possibly use, it was used for charging a remote control car battery? Could I put that to use for powering up this circuit ? Does the current listed on the motor and of the power supply have to be close in value or could they be completely different ? I would really appreciate if you explained this to me. Thanks.

    1. The power supply rating should have a voltage rating exactly matching to the load……current is immaterial, but should be higher than the load, if it's lower, the voltage will drop.

      The mosfet can be anything…just needs to be rated at least twice to the load rating, if it's higher no issues, but preferably shouldn't be lower.

  15. HI,
    You may misunderstand me… You know my motor have 18k rpm in no load and about 5k rpm when connected to 4v 3 amp battery and about 10k rpm on 6v 4.5ah battery.

    For got about my stupid TDA7274 circuit. its giving me about 700-900 rpm to me which is not any value and its not giving me any airflow that can I feel from 12" far.
    So I want to through the Circuit to the dustbin as its useless and the IC is getting about too many hotter, you can feel that it can cook your rise in 10 minutes. So I am pretty sure the circuit will not last long and it can be make any damage as its hotting up.

    Now I want your help, I hope you seen my motor and which fan I connected (

    Please give me any circuit that can drive my motor with this fan (load) at 2-4 k rpm. I found that my motor is stable on this RPM but it getting hot if I it go to more that 5k rpm.

    Please don't leave me alone here. want your help,

    Awaiting to hear from you.


  16. Hi guys could I run a 50k varible pot without modding the caps? Also running a 24v motor 500w can I use 3x irf3205 in pallarell? Thanks

  17. SIR, I made this and it works amazingly, thank you very much i will make a youtube video of my use of it in a ebike if i get it going.. richharrisonline is my username 😀 Cheers and thanks again!

  18. Hello sir, if i wanted to hook up a heat sink to this circuit… could i just add the positive of the fan to pin 7 so the fan motor would only go when the motor is engaged… would this work, thanks 🙂

  19. Dear sir, what value of resistor do i need to substitute in order to make my adjustable pot work from 0 – 100 % power with only a 1/4 turn of the pot? or what pot should i substitute? it is for a ebike throttle. thanks a lot 😀

  20. Wow, this is the best answering I've ever seen for a tech blog – good job Swagatam! I've seen both your 100% motor control circuit and this one – which do you think would be better to control a 10 hp DC motor (10kw – 97 volt, 90 amp) on a dune buggy? To use this circuit I would supply the 97v to the motor and 12v to the IC, correct? I would need to get a 100v 100a mosfet though, right? Thanks man – you're awesome.

  21. So much SWAG! 🙂

    Im trying to build a PWM controller for a dc motor that runs a fluid pump. I know it would need 0-100% control, but I also think that your constant torque circuit would be better. (since i need to deliver exact amounts of fluid) However the constant torque circuit you provided shows a bi-directional motor and I could not follow your text instructions for making it single direction. I would like to be able to adjust frequency, and pulse width. Circuit will a regulated 8v from the batterypack/power supply. Can you maybe point me to a good instructions page to build for this? (motor "on time" will be determined by a lookup table using a micro processor, but thats a whole nother issue)

    1. Thanks JC,

      Please refer to the following diagram, you can try this design:

      Connect your motor across the drain and positive of the circuit…please ignore the bridge rectifier it's not meant for us.

      The shown PNP transistor is BC557 and not BC547 as wrongly given in the diagram.

      The pot at pin5 of IC2 can be used for controlling the speed,

      The mosfet can be replaced by a power transistor, if desired. In this case use ordinary 555 IC, and not 7555.

  22. Thank you for you speedy response. I would have commented earlier but i was waiting for an email telling me you responded. (never came) could you please verify for me the value of R4. i believe that should be 2k ohms.

    also one other thing, From what i gather, adjusting pot at pin 5 will control the duty cycle, but could you please explain how i would go about adjusting the frequency should i need to. I have built your other PWM circuit and it worked great. (using one 555ic)

    I remember a time back when i was in air force tech school when i could of done all this with my eyes closed. they were very thourough. its amazing to me how only in a few years i could forget so much!

    1. My replies here are supposed to reach the commentor in their email IDs, you should find these discussions in your email inbox, according to me.

      Although the frequency has no relevance to the motor speeds, it can be controlled by varying R1 or the 180k resistor value.

      I am sure the discussions here will help you to restore all you had learned back:)

  23. hi sir
    we make 12V PWM based dc motor controller circuit. it work properly but it give short circuit current 4A. we want to get 15A short circuit current at output. please guide us.

    1. hello sir…
      Thank you for your guidance.I have another query. we want to modify this circuit through 3 mosfets,one 555 timer using 12v supply of car battery and get 15A short circuit current.what we do for this?

    2. hello sir
      sorry sir,i have another query. which value of resistors connected across the gate and we want to get max 15A current on the output. our input supply is 12V, 4A. Is this power supply suitable for our circuit?

  24. good afternoon sir
    we design 12V PWM based dc motor controller circuit.It work properly. but we want to get fix 2A current at output so we want to remove the pot and connect the resistor.sir, what value resistor we connect ?

  25. Is this circuit 0 to 100% duty cycle? I want the frequency to be constant 60 Hz. How would I do that?
    Using this formula? F = 1.44(VR1*C1)
    Based on your circuit you put 100k for vr1 and 0.1u for c1. Frequency will be 0.0144 hz?

  26. Hai, I bought one 12v dc motor. I connected it directly to the 12v adapter. Then the motor is running in a pulse mode. Means like clocks seconds needle moving. running, stopped, running, stoped. like that. When i asked abt this to the shop man, he told that the motor got damaged due to directly connected to the 12v power supply, a 12v motor should not directly connected to a 12v power supply, It should connected through shunt (resistor). But he dont know what resistor have to put.
    Could u tell me, is that correct which he told?? and wat resistor i have to connect between the motor and the power supply if I want to connect the motor directly to the 12v power supply?
    Now I bought another motor which is rated 12v ,0.28A. I like to connect this motor to ur above circuit. so still do I need a Shunt (resistor)?? and wat value, rated mosfet I can use for ur above circuit?

  27. Hi, that's completely rubbish…if the motor is specified to run at 12V it can be safely connected with any 12V supply (regardless of the amp rating of the supply).

    shunt resistor may be required for protecting the power supply (SMPS) from the back emf that may be generated by the motor…. so its the power supply that may need protection with a shunt, not the motor.

    The above may be true only with big heavy duty motors only….not in your case.

    1. Thanks for the clarification… so the shop man cheated me by giving a damaged motor itseems :-(… Now am having a 12v, 0.28A DC motor. I like to use this motor in ur above circuit. so Could u tell me that wat mosfet i can use for this??

    1. An IRF840 mosfet could be tried, power supply should be DC and as per the maximum rating of the motor….for RPM you'll have to procure a ready made RPM meter and integrate it with the motor.

  28. Dear Sir,

    I am a beginner.

    Can I use the above circuit for my treadmill with 180V 6A 4200 RPM DC Motor. I would like to use the mill only for normal walking of about 30 to 45 minutes in normal speed.

    Can I reduce the RPM to my desired speed (only for walking with speed of 4 to 6 KM/hour) using the above circuit. If I use the POT, what would be the changes in the RPM when the POT gets in to its maximum and minimum positions. If I can use the above circuit, pl suggest me the appropriate MOFSET for the above load.

    I went through all your reply and it is interesting and valuable. I really appreciate your patience and commitment.

    Sir, my thanks to you in advance

    Shine K P

    1. Thank you dear Shine!

      yes, according to me you can use the above circuit for your said application.
      The maximum achievable speed is near 95% and the minimum is near 5% so it's pretty efficient with its control spces.

      You can use IRF840 as the mosfet.

    2. Dear Sir,

      Sorry for bothering you…..

      I tried this circuit but in between got stuck because, I am not finding any way to bring 12V dc to IC 555 as my rectified DC is 180V, which I am using for motor, in the board. I believe, I cannot connect LM7812 directly to this volt. Can you please help me on this?

      Thanks & regards,
      Shine K P

    3. Dear Shine you can use any standard 220V to 12V AC/DC SMPS power supply for this….you can get it in the local market,

      even your phone charger will work for the time being.

    4. Dear shine,

      the drain will connect with the (-) of the motor, please see the diagram above.
      The (-) of the 180V will become common with the (-) of the 12V supply…..the motor (+) will connect with the (+) of the 180V supply

    5. Dear Sir,

      I tried this

      1)Motor didn't run when the power on
      2)When I turned the POT, it started running but immediately 555 got burned and MOFSET as well LM7812 also got hot.
      3)Even though the smoke was comming from 555 motor was running.
      4)I checked the circuit and found no short circuit.

      Sir, what could be cause for this? Can you pl advise me…..

      Thanks & Regards,
      Shine K P

    6. Dear Shine,

      I recommended using a separate 12V AC/DC adapter for powering the IC stage…not a 7812 IC so please build it again and power it as suggested.

      also connect a 6amp rectifier diode right across the motor coil in order to safeguard the fet from motor back emfs.,

    7. Dear Sir,

      I didn't get 12V AC/DC Adapter but got 15V AC/DC from my nearest shop. That is the reason, I used 7812 to get the regulated 12V DC to IC.

      1)Should I use 12 AC/Dc adapter and remove 7812?

      2)Sir, I joined both -ves (180 and 12) and grounded wherever it is mentioned in the circuit, even to source of MOFSET. Hope it is correct.

      3)Offcourse, I can connect protector diode and will try again.

      Thanks & Regards,
      Shine K P

    8. Dear shine,

      yes, 7812 with 15V input is perfectly fine, and making the negatives common along with the fet source is also perfect….I think attaching the diodes across the motor should solve the problem.

    9. Dear Sir,

      I connected the 6A4 diode across the motor, now IC and 7812 are okay but MOFSET is getting hot. I think, the MOFSET got damaged while it got heated last time.Now motor is running in its full speed. No control on POT and MOFSET is getting hot also.I put heat sink for MOFSET and 7812. I noticed, even without inserting 555, motor is running in its full speed.I checked the POT and it is working fine. Let me change the MOFSET. I would require your hep sir….sorry for bothering you.

      Shine K P

    10. Dear Shine, if without IC the motor is running that surely indicates a faulty mosfet…try using two mosfets in parallel for ensuring better safety to the mosfet and reducing heat dissipation

    11. Dear Sir,

      Thank you….noted your suggestion. Let me try this also. Can you please advise me on below

      1)PIN 7 of 555 will be connected to GATES of two MOSFETs seperatly. Do I need to need to add 10k again? ie Do i need to add 10k before each GATE?

      2)DRAIN of two MOSFETs will be joined together and connected to -ve of motor

      3)SOURCE of two MOSFETs will be grounded.

      Am I right sir?

      Shine K P

    12. Dear Shine, the 10k need not be repeated, pin7 needs to be connected with each mosfet gates via separate 22 ohm resistors.

      next, drains will join together and connect with the motor negative, sources will join together and connect with the ground

    13. Dear Sir,
      I tried with two MOSFET and connected 22 ohms resistor also. It was working fine.When I applied the load (I started walking), the motor was about to stop but when I increased the POT , motor started running for my desirable speed for walking but suddenly MOSFET got burned. There was some noise from motor while in low RPM. 6A4 diode is already connected across motor coil.

      Can you please advise?

      Shine K P

    14. Dear Shine, that's perfect, the IRf840 are rated to handle 500V at 8amps so it shouldn't be a problem…there could be two possibilities either your motor is drawing over 16 amps when loaded or the mosfets are not original.

      you can try connecting two more (4 total) mosfets in parallel in an identical fashion as explained previously and check the response

  29. Dear sir,
    I am a mechanical guy,currently working on an electric vehicle and i want to control the speed of my motor using pedal . i am not getting a controller for my motor please help me to build my own i''ll be highly thankful
    Motor Specifications are 36volt,43ampsand 1.5hp brushed dc motor

  30. Hey Swagatam, I am an engineering student trying to build a pwm to control a 24v 750w motor. This will be used to power a 250lb vehicle with a driver weight of 150lb. I am a mechanical person and am new to circuitry. I can't seem to view your schematic that is supposed to be with this article. But do you think it will work with my application? I plan on using a potentiometer in order to control the speed of the vehicle. Thanks in advance

    1. Hi James, yes definitely the above shown design can be used for your application.

      Just make sure the FET is rated to handle 50V 1000 watt, and the 555 IC is supplied with a stepped down 12V through a 7812 IC regulator.

  31. Dear Swagatam, I want to use this pwm motor controller circuit to controll hydrogen on demand production of a hho cell on a test generator. Hho gas boosting on cars engines might also be tested so I want to use a standard pwm circuit that will be able to test hho production for both small & bigger engines. Would it be advisable to go from start & use for instance a higher current 12V 55Amp Mosfet Transistor plus more protection on the load side? What do you suggest? Then last but not least, are you aware or knowledgable about producing hho gas by making use of a resonant frequency circuit to create harmonic resonance or oscillation by making use of a 555 timer chip & a variable pot in the circuit to set the frequency of the circuit on the water's natural frequency in the hho cell that acts as a water cap & disassosiate the water molecules into a hydrogen & oxygen gas mixture without making use of any electrolyte in the hho cell for conduction. Or if you know a circuit that works well in this respect could you please let me know were I can find it.
    Thank you for your valued electronic knowledge & unselfish input we all really honour you for it.
    Best Regards

    1. Thanks so much Daan,

      I think the above 555 circuit can be used without any issues for your application and it's a good and a reliable option to begin with.

      The mosfet parameter is not relevant to the circuit, that means any mosfet with any voltage/current specs can be used with the shown circuit.

      I have not yet researched on the concept of a resonant HHO generator but I think it's an interesting topic to investigate on, and I will surely look into it and try to post an pertinent article. Thanks and do keep in touch!

  32. Hi swagatham,
    I tryed this circuit in bread board,I'm using 12v, 7 amp motor 2nos connected parallel so the load is 14 amps. It is not working when I tune the pot in one place motor start running in full speed and after that not working. I do no where I made mistake please guide me.
    IRF540N is the MOSFET
    Waiting for your reply…

    Swarajit Alakananda

    1. Hi Swarajit, first confirm whether your 555 is working correctly or not.

      remove the mosfet and the motor from the circuit and connect an LED with a 1K resistor across pin#7 and ground of the IC….now adjust the pot around and see if the LED alters its intensity from zero to max and back….if this is not happening then you could assume something to be not correct in your circuit.

    2. Now my circuit is OK swagatham, the problem is I can't feel much difference in the motor speed

      If i use a high amps MOSFET for low amps motor will that be an issue …..
      I'm using IRF 540N, For a 7 amps motor..

  33. Hi swagatham,
    Thank u so much, now the circuit is working perfect, I have two more doubt.
    1.) Can I use a common (parallely connected )potentiometer for two circuit ( as I'm using this for a robot car, there will be two motor left and right both working by different but speed should be maintained same)
    2.)I want to switch frequently so If I use the switch on after the MOSFET while the circuit is on continuously I'll control the motor through the output, is that cause any damage to circuit?

    1. Thanks Swarajit, I am glad to know it's serving the purpose.

      1) you can use a dual pot for implementing a simultaneous operation of the two circuit's PWMs, in sync

      2) you can use a DPDT switch in series with the motors, it won't do any harm to the circuit functioning.

  34. Hi swagatam.
    I'm trying to use this circuit to control speed on my radiator fans in my truck
    (dual fans, 15 amps each, wired in parallel) based on temperature.
    the temp sensor is fastened to ground with one wire out

    what I came up with was to put the sensor between the 555 GND so as to vary the gnd supply to the 555 based on temp. I know this is not the ideal way but is all I could come up with.

    Also wondering about mosfets, I have a couple that are rated at 30vdc and 70 amps
    so by all means one of these should do the job right?
    …just find it hard to believe that one of these could power such large fans..
    any help will b greatly appreciated, thank you.

    1. Hi Henry,

      your idea regarding using the sensor with pin1 of the IC is technically incorrect and inapplicable, so that won't be feasible.

      However pin#5 can be targeted for delivering the purpose by using BJTs, mosfets won't be effective, if possible I'll try to figure out the design….

      I would be interested to know about the output from the sensor at the peak temperature (at the desired cut of threshold)

  35. R/Sir,
    I am willing to control 2hp dc motor.having field 220volt @ armature is 200volt.which cct. is suitable to control the motor by armature supply variation.These motors are used in printing industry. I hope that you will give me a proper guidance.

  36. R/Sir,
    In my design I used 220v dc by using 35 A bridge to power Field supply of the motor.@ I used 6A4 bridge to power Armature supply.But when I am connecting the said cct. one 6A4 get shorted.Then I changed the supply bridge to armature and vice versa.till one diode is shorted.The motor is 1.5 hp @ rating 8amp. named dc shunt. So sir please give suggestion to work this motor. Anothr thing is I was used another cct. having 2n5269 in its output.I used bridge for field. and 40 volt dc for armature. the ccct. works nomally.but actually operation is on 220v.this is the total information about this project.since last month I am following your site. which is very nice @ halpful to all. Mostelywhen I am reading the reply from your site it looks like we are siting in front of you @ you are giving explanation of the project.
    lot of thanks.@ wating for the reply.

    1. Mukund, I do not have much experience with motors that are designed with two winding, I'll have to study more and only then I would able to suggest you correctly whether your implementation is correct or not.

      I'll try to do it soon, once I finish other pending assignments.

      keep in touch until then….

    2. R/Sir,
      After long time I am making contact.Sir If there is any Idea about controlling the pwm motor with field and Armature with 220volt supply? hopping to be excused. Waitin for your plesant reply.

  37. hi, swagatam bro my teacher gave me your circuit as my semester project, but he add some more thing like mathematical modeling and transfer function of this pwm circuit. will you help me to find out these…please

  38. Dear sir I use this circuit and found wonderful working …nut now today I have a treadmill 220v dc motor so please guide me that this circuit will work properly or not if yes then changing will be required ? Wating your good response with thanks

  39. Thanks swagatam for your good response , I changed mosfet but found not working . Accrording to me that I apply only 220 v dc to only mosfet not connect ground and positive through resistor same as traic to 555 power supply . Sir is I am correct or not ? Dc motor is 1.5 hp. 5ampere . Sir plz send me circuit or guide me with special thanks

    1. which mosfet did you use? the ground connections (symbols) shown in the diagram all needs to be connected together (made common)….in other words the 220V (-) needs to be connected with your 555 IC's 12V (-)…..I hope you have use a 12V DC supply separately for powering the 555 circuit,

  40. Dear sir thanks for your good response , because I use other mosfet for 220 v 5,ampere dc motor but the out put voltage controled from 145 v to 220 v . But my requirement is 0v to 220 v variable… So plz guide me I m waiting plz sir

  41. Hi Swagatham
    I assembled this circuit to control the speed of a 24vdc, 1ampere, 15000rpm motor(mixer motor from an automatic coffee vending machine). It is working perfectly. But at very low speed, the motor does not rotate. It makes only a humming sound.
    When I control the 100k pot, the LED parallel to motor also works from 0 to full brightnes.
    Then I connected 470md capacitor to drain and source. Now I noticed the LED always stay at full intensity. Stil I can control the speed. But now POT at lower side the motor rotates at slow speed, say 10% or 20% duty cycle.
    I need to modify the circuit with that 470mfd and 0 to 100% duty cycle. What changes should I make..?

    1. Hi Anil,

      the circuit is actually providing 0 to 100% PWM output but your motor is not responding at lower PWMs due to lack of torque, you can try connecting the capacitor right across the motor leads and see if that helps, because I cannot see any other possible modification for rectifying this issue in the circuit.

  42. Thanks
    Your circuit diagram is ok. I added 7812 for 12v for circuit section. 24v for motor. The mosfet I used is 50n06.

    At present I don't have a 470mfd or more value with voltage rating greater than 25vdc to try parallel with motor.I will try once I get it.

    My problems started after I connecting the 470mfd to drain and source. But I need it to avoid buzzing sound at low speed.

    Anyway once again I connected 470mfd to drain and source. I removed led parallel with motor and connected to mosfet gate and ground. Now the led brightnes varies with motor speed. So visual indication issue solved…..! ( Without the 470mfd, led brightness–parallel with motor –varies with motor speed…….! ).

    But motor still rotates at speed more than I want even if 100k pot at its minimum setting. I hope I can solve this by adding a fixed resistor at the middile pin of 100k pot. Not yet tried, will try later..

    I am sharing this post here for helping other readers.

    1. Hi Swagatham
      At last I found an answer for my 470md related problem from your one another circuit.

      Please read the 2nd paragraph above the circuit diagram starting " However only the average DC voltage is finally fed to the cell phone due to the presence of the 10uF……."

      I suspect, my 470mfd did the same roll of the 10mfd in this circuit. So I cannot attain very slow speed after I connected the 470mfd accross the drain and source.

      Without the 470mfd, I can control speed of motor + and brightness of an LED with 2.2K series resistor across the motor from 0% to 100%……!

    2. Thanks Anil, yes that could be the issue, the 470uF might not be allowing the motor to switch OFF completely during the OFF periods of the mosfet. You can try decreasing the 470uF to 22uF which might help to control the noise level of the motor as well as allow complete control of the motor speed.

  43. Hai, I bought one motor and one 12v 2amp dc adapter. when I connected the new motor directly to the adapter, the motor is 2 seconds spinning, 2 seconds stopped, spinning, stopped,contiues.. Then I tried with another similar motor (Removed the motor from pcb drill machine,Rating:12-18V, 30watts) with the same adapter, the motor is spinning good. Then I connected both the motors in parallel with the same adapter. Then both motors are spinning good. so can u able to find the reason why the new motor is not spinning continuesly when I connected it separately with the adapter?
    And is there any way to find the rating of a motor? Bcoz nothing is mentioned or labled on the new motor. Its plain.

    1. Hai, may be it's due to some improper connection inside the motor or the adapter…because if both the motors are running together then they would do the same individually too.

      Connect an ammeter in series with the motor wire and you can get the amp consumption on the meter while its running.

  44. Using same the circuit with triac it can run AC motor….but how???
    How many triac are required?
    What changes are required in the circuit?
    Which triac I can use any specific for high voltages?

    1. connect the gate (left lead) of the triac with the 555 output pin through a 1K resistor

      connect the right side lead with the negative of the circuit.

      connect the the center lead with one of the wires of the load….connect mains with the other wire of the load and the negative of the circuit.

  45. hi sir,

    i want to make a wireless system to control 2dc motors.

    2 dc motors180v,1.9amp. this ,motor is connected to a AC source.1 bluetooth is connected to a computer as signal sender & 1 as receiver at motor side,i need a motor driver circuit and ac to dc converter circuit also

    1. Hi Lidya, you will require a PWM transmission for this, I have not investigated how to send PWM through bluetooth, so I will have to do some research first before commenting….I'll try to upadte it soon

    2. Hi Sir ,
      Thank you for the information & the immediate response.

      I think,this was the mistake i made in explanation.

      The transmitter bluetooth just send the data from the computer (how much the user want to controll) to the receiving side.
      At the receiving side we receives the data from receiver bluetooth & send to ANy microcontroller(i would like to use PIC). This Microcontroller makes the PWM signal for the motor.

      My doubt is, can i connect this specified motor (180V,1.9A,1/3 Hp DC Motor)with the controlling signal?(in microcontroller side we using 5V,) to convert AC for 180v,19A DC Motor.

    3. Thanks Lidiya, got it now.

      you can use the mosfet/motor driver configuration that's shown in the article above and integrate it with your available 5V PWM.

      But mofet might not trigger correctly with a 5V source so you can try replacing the mosfet with a BJT MJE13005.

      converting the 220V AC to 180V DC could be difficult. A possible solution could be through an appropriately wound coil over a laminated iron core which would drop the 220V AC to 180V AC, which could be further rectified with a bridge diode for the final DC

  46. sir——–i have 35 v load needs 3.3 A current—-around 120 w—–i am providing 12 v dc separately to 555——-

    ——my doubts are

    1——- should i connect 35-0 v dc directly to motor +ve terminal and neutral wire to other side as shown——figure

    2—–approx weight size of heatsink for 200 watts for mosfet

    3—–i have 10 k pot will that be ok

    4———-1 kohm of ??? watts resistor should be connected wiper of pot and 3 pin —prevent pot from burning———–i have a doubt

    5—-1 peice mosfet like irf 540——sufficient for how max watts

    ————-thank you——————

    1. Rahul

      1) yes you can do that, but first test with a lamp of the same specs for confirming the actions.

      2) heatsink will need to be optimized with practical experimentation.

      3) yes will do!

      4) pin#2 has high resistance so that may not be required but you can add it, there's no harm

      5) more than 200 watts if heatsink is adequate

    2. sir————-thank you a lot————-irf 540—datasheet shows 150 w at 25 celcius temperature———–but in real life almost it is impossible—-to maintain 25c so—-i have to keep 2 irf 540 in parallel——–now there i have some problem—–i tried earlier also with other voltage regulators could not make them parallel—-hogging issue 1 regulator taking more load than other—–

    3. Rahul, Just attach the mosfets over a single common heatsink without mica isolator…..this will ensure there's no hogging issue, and by the way mosfets behave oppositely to BJTs as far current hogging is concerned so anyway this cannot be a problem.

    4. dear bos,
      why this mosfets damage again and again in motor control circuits. what is the happaning. if the once damage fet it canot re use longer reaplace new fet. but if we reaplace new circuit it works more longer. so if we reaplace fet we need to change any other parts in the circuit ? wich parts may be damage with fet ?

  47. Hi sir, is putting a freewheel diode across mosfet necessary as flyback from motor can damage mosfet, and what can I do if I don't have a freewheel diode, can I use make freewheel using 1N4007 and 1n4148 in combination if yes then how?

    1. Hi Abhishek, the value of the diode will depend on the motor current, if it is a low current type motor not above 3 amps, then a 1N4007 can be used…..combination of parallel diodes may not work correctly.

      however today all mosfets have built in freewheeling diodes.

    2. Hi Abhishek, it will be difficult for me to troubleshoot a fault in your circuit without practically checking it…the above design is a fully tested and confirmed design, and it is a standard PWM circuit so it cannot be wrong.

      you can do one thing, connect an LED across pin#7 and ground, and check its brightness in response to the pot adjustment, if it varies then your IC 555 section is good

    3. Hi sir swagatam, bravo, I modified circuit as same shown above and it's perfectly working, now speed is also controllable, thanks for your guidance. New question, I had not added 1N4007 to irf540, so now should I add it and it's not operating 12vdc 775 motor general purpose pcb drill motor, it's 15w. I'm using two 9v battery.

    4. That's great Aabhishek, however your previous circuit is also correct and should have worked…investigate why it did not work.

      it is better to add the 1N4007 diode for ensuring 100% safety to the mosfet.

      9V PP3 can be used only for very low current applications, motors will never work with these batts, you should use a bigger battery or many AAA 1.5V cells together

    5. Hi sir, through 9v small motors are perfectly working but the 12v 775 motor (15w)not even move. All other motors are perfectly working. Should I use 12v 7.6ah lead acid battery, are you sure 7.6ah lead acid battery will not burn the circuit or ic

    6. Hi Abhishek, even a small motor will quickly drain your 9V battery, so it is not recommended for motors.

      you can use 7.5AH batt, it will not harm the motor as long the voltage is correctly matched.

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