Treadmill Motor Speed Controller Circuit

In this post we discuss a simple, accurate, high torque treadmill motor speed controller circuit which may be effectively installed in similar units for acquiring PWM controlled variable speed feature. The idea was requested by Mr. Samuel.

The Circuit Request

I've a treadmill whose power failed had been imported from china and it's like they can't help after negotiating with them..guarantee is only meant in their x-try.

So, am asking, how would you assist me in designing a power supply that will control speed and change of direction of the treadmill movement as well. I'm and forever will be glad for your work.

Looking into the specs of the unit, the switching relays are specified with 10A ratings. I also had a view of the motor and it was written 180Volts on it.

This is the information i got sir. They also had a cautionary notice that the T.Mill shouldn't be run beyond 2hrs continuously. I hope I've given the best for the best.Thanks sir. Stay blessed now and forever! best moments!

The Circuit Design

Here's a simple PWM based motor speed controller circuit which can be used for controlling a treadmill speed right from zero to maximum.

The circuit also provides an instant bidirectional stop and reversal of the motor rotation by a single flick of a given switch.

Another interesting feature of this circuit is its capability of sustaining and balancing optimal torque even at lower speeds ensuring a continuous working of the motor without stalling it during extreme low speeds.

The circuit of the proposed treadmill motor speed controller may be understood with the help of the following points:

Here the two 555 ICs are configured as PWM generator/optimizer for acquiring the required speed control of the connected motor.

Circuit Description

IC1 works as a frequency generator and is rigged at around 80Hz, any other value would also do and is not anyway critical.

The above frequency from pin#3 of IC1 is fed to pin#2 of IC2 which is wired as a standard monostable. IC2 responds and starts oscillating at this frequency, forcing equivalent triangle wave frequency at its pin2/6.

The above triangle waves is instantly compared by the set potential at pin#5 of IC2 creating an equivalent level of chopped PWM at its pin#3

The preset or a pot positioned at pin#5 of IC2 forms a  potential divider network for a selectable fixing of any voltage from zero to maximum supply voltage at pin5 of IC2. This level is directly translated through optimized PWMs at pin#3 of the same IC as explained above.

The PWMs are fed across two sets of NOT gates via an SPDT toggle switch.

The NOT gates which act as inverters provide the feature of instant toggling of the motors rotational direction by a mere flick of the SPDT switch.

The resultant PWMs from the selected NOT gates finally reach the transistorized bridge network that holds the motor between them for implementing all the specified features discussed above.

These transistors should be rated as per the motor specifications, and the voltage across this bridge should also be as per the motor requirements.

Treadmill Motor Speed Controller Circuit


As rightly suggested by one of the dedicated readers of this blog, Mr. Ivan, a 180 V treadmill motor can be simply controlled through mains phase chopping concept, normally incorporated in all commercial dimmer switches for regulating home fan speed.

Using A Dimmer Phase Chopper Circuit

Shown below is a modified dimmer switch circuit design which can be effectively used for regulating a 180 V treadmill motor from zero to max:


182 thoughts on “Treadmill Motor Speed Controller Circuit

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. Hi, Could you explain how a constant torque at low speeds is achieved? My treadmill bogs down slightly with each step when I get below about 1.2mph.

    • Constant torque is achieved by the use of PWMs which prevent the devices from unnecessarily heating up yet allowing them to conduct fully during the ON states of the devices.
      So it's like allowing the devices to conduct fully with full power yet only at the desired slower speeds by breaking their conduction many number of times per second.

  3. Hello
    My treadmill motor is rated for 130VDC and 15a. I plan on using 120vac(line voltage) and a bridge rectifier to power the motor. What type of transistors would I use for T2-T5? I don't recognize the symbol you used. IRF540 mosfet is only 100v, I think. any advice is welcome.

    Also, what is the symbol just left of C1? I apologize for my lack of knowledge.

  4. I'm putting together a shopping list for this project. 1/4 watt metal film resistors would work, right?
    C3 is listed as 1uf, what voltage and style of capacitor should i get? The other caps I was going to buy 50VDC ceramic disc. My motor is rated at 130VDC 15A, i was going to power the motor with 110VAC thru a bridge rectifier, any ideas on what transistors to buy? IRF540 is only 100volts One last thing, what is the symbol just left of C1? I apologize for my lack of knowledge.

  5. Thanks for the great design! Why are the BJTs better here, as I understand BJTs are preferred for low current applications, while MOSFETs are for high power functions.

    Matt M

    • If the requirement is above 30 amps mosfets could be preferred…mosfets require stricter parameters while configuring compared to BJTs therefore sometimes become difficult to handle.
      however in the above design mosfets could be used since the configuration does not demand a high side driver due to the involvement of both n/p mosftes..

  6. Thanks for this fantastic circuit diagram. I'm new to electronics so please excuse me if these are dumb questions. Would there need to be any programming done to make this work or does the hardware do all that automatically? Also, I wouldn't need the reverse feature and a simpler circuit would definitely be easier for a beginner like me. Could you show us what this circuit would look like without the components necessary for the reverse feature and how I could make this work using 110vac i.e. Where would the ac come in and where would it be rectified? Thanks again!

    • Thanks very much Michael, no programing is required for the devices all the ICs come preprogrammed, just have to wire them up in the shown manner.

      If you are not interested in the reversing feature the circuit definitely becomes much simpler as shown in the following image:

      ignore the four diodes shown at the top which was drawn for some other similar application need.

      the mosfet upper lead which is drain needs to be connected with the motor negative, while the positive of the motor will connect with the 110V DC or whatever may be the motor operational voltage spec.

      The circuit would however need to be powered through a 12V AC/DC adapter specified to take the input from a 110V AC, nowadays such adapters are suited for any input right from 85V AC to 285V AC, so it won't be much of a concern

      The shown pot could be used for the required speed control.

  7. Many thanks Sir for this publication.
    I'm sorry for dump questions but I'm newbe to electronics.
    Will this work with my 240VDC/12A motor?
    How many of this CD4049UBE CD4049 4049 IC Hex Buffer/Converters do I need to order?



  8. Dear Swagatam, many thanks for your fast replies.
    I’ve managed to put everything together and pluged in. Unfortunatelly when my treadmill motor (220VDC/3.5hp)
    started to turn a smoke come out from one of the BJTs.
    Now it looks like all four of them (mj11021pnp-mj11022-npn) has gone, cos I can’t see any reading between base-collector, emitter when testing them.
    What I’ve noticed afterwards that it was a bad solder between R6 and bases of T2,T3.Virtually no connection at all. Also I’ve used 1N4744 as a D1.
    What do you think Sir. Any suggestions?

    Regards, Wes.

    • Dear Wes,

      A bad solder won't cause a burning problem according to me, I think the treadmill motor could have exceeded the max amp rating of the BJTs,

      Replace the circuit with new transistors and try operating the treadmill without any load, check the response,

      the other reason could be wrongly configured BJTs

    • Many thanks Swagatam.
      New high voltage transistors just been ordered. You're right. After closer examination it looks like BJTs were wrongly configured. This cause them to burn.
      So do you think that I could use four 6A4 rectifiers in the bridge instead of 1N4001 as it is in your cuircuit?
      Talking about Zenner diodes, I'm using 1N4744 instead of 2v7 as a D1 which is a Zenner diode in your circuit. I don't use them in the bridge.

      Regards Sir,


    • OK Wes, that's good! yes 6A4 is the minimum requirement for the bridge diodes, 1N4001 will not do as these will blow of due to the high motor back emf.

      I mistakenly thought that you had used the zener in the motor bridge circuit,….surely it will do in place of the shown 2.7V zener

  9. Mr. Majumdar, I have a similar problem. I have a treadmill which controller chip has failed and now i would like to build independent control of the motor. It is PMDC (Permanent-magnet DC) motor, 180V, 6.8A. I want to control it's speed from zero to max by powering it from 220V AC power grid. Can you give some circuit similar to the above one, but for 220V AC, please?

    • Hi Ivan, it's showing the peak voltage, once connected to the load the voltage will come down to the specified level, however still it could be not so safe to apply the pulsating peaks to the motor, so I think you will have to get a suitable auto-transformer designed from a transformer maker. Tell him to design a transformer which would be able to supply 150V/6amp from 220V….this output can be then bridge rectified and filtered to acquire the required 180v for your motor.

  10. Sorry for my last post, I knew that this is the peak value of the voltage formed by the capacitor, but the post was already on its way. At all I intend to use this circuit:

    I have also some differences – I need one direction and have 180V DC motor at 2.2HP (that's 1640W of power). It seems that the circuit must be without those NOT gates because of the single way rotation and I'll need only 2 power transistors (in parallel oor in sequence). I don't know only what should be those Darlingtons?

    • Yes, you are right the NOT gates won't be required in the referred diagram.

      For the transistor you can simply use a single high voltage Darligton transistor such as ST901T with pin3 of IC2 for the required implementation.

  11. Just a single ST901T?! I have 1640W of power which makes around 9A of current at 180V and the Icmax of ST901T is just 4A?! The motor will not be loaded at the maximum power rate but still isn't 4A too less? How about 2 or even 3 ST901T's in parallel?

    • sorry it won't work, I seems I missed the amp spec of the device.

      you can either search for a suitable single device or connect many of these in parallel, just make sure all of these are mounted over a single common heatsink.

  12. Hello, mr Majumdar, I have something much simplier in view with respect to 180V DC treadmill motor control powered from 220V AC grid. The parameters are:
    – 220V AC power grid
    – 180V permanent magnet DC motor 7Amps motor
    – main control element a SCR (thyristor) simultaneously acting like rectifier and control element with phase controlling circuit
    – a capacitor in parallel after the thyristor acting simultaneously like smoothing element for the phase-cutted sine and voltage-raising capacitor (just like in the last circuit you offered me).
    – a SCR control circuit that uses phase-cut method – cutting the sine at different angles in order to get different voltage values above the motor.

    I think it will be much simpler than the two 555 timers PWM and Darlington stages.

    Best regards!

    • Hello Ivan, yes that's a smart idea, since the load is 180 V rated using a dimmer switch circuit as the speed controller is definitely possible, the motor output will only require a bridge network and filter capacitor for the AC to DC conversion.

      If possible I'll try to update the design in the above article soon.

    • Thanks Ivan, The diameter of the core could be such that it accommodates the 200 turns comfortably, it could be done over an iron bolt or screw…but the diameter of the wire should be more than the indicated 0.6 mm since the motor is rated to carry high currents…a 1.5 mm could be tried initially.

  13. Hi, Mr.Majumdar, the dimmer circuit simply does not work, I did 3 times, the load works always at the grid's voltage (220V), no matter the potentiometer setting. All the elements are the same as required, the circuit has been checked maybe 30-40 times, everything is correct but it doesn't work. I also did a circuit with PWM and a MOSFET, the same fails everytime at nearly half turned potentiometer and the engine is even at idle.
    I never imagined that controlling the speed of a DC motor can be so difficult!!!

  14. Mr. Majumdar, I didn't say anything about your first circuit, at least my was with MOSFET stage unlike yours. As for the second one, I tried alll the things you said – removing the engine and the bridge and using a 100W lamp as AC load. The result was the same. Anyway . . . . Now I found another circuit in one of our old elctronic magazines (I'm from Bulgaria). Unlike your second circuit it uses thyristor (SCR), not triac.

    It's used for drill machines and can power a engine up to 800W. The list of elements is in bulgarian, that's why I'm not posting it here. As in the circuit above, a bridge rectifier and a smoothing capacitor should give my treadmill DC motor what it needs . . . . . I hope.

    • Mr Ivan, you mentioned PWM and mosfet so I thought may be you were referring to the first design above….

      anyway the second circuit is a very basic fan dimmer switch design that we use in our homes for controlling fan speeds or light intensity….i have tested the circuit thoroughly and have one installed in my house….so if an AC load is not working in your circuit then definitely there's something incorrect in your circuit assembly.

      The image that you ahve provided will controll speeds upti 50% only and will create lot of jerk at lower speeds….i already have a similar design posted in my blog here:

  15. I thought the thyristor will work like half-wave rectifier together with the phase cut-off process. This is because of the voltage differences of the grid and engine (220V and 180V respectively). A lot of these circuits are widely used for motor speed controls. By the way the author of the circuit I uploaded says that the C1 capacitor's value is determined experimentally (between 1 and 10 uF) to choose less jerk and max torque (something like compromise between both). If nothing happens with my circuit, I'll do your first one.

    I have another question – what will happend if the value of the pot increases rapidly when the engine goes at slow speed? By my opinion the voltage above the engine will also increase the same way and the power element (SCR, transistor) will fail immediately. I mentioned that the treadmill has opto-tachometer originally. I think it gives feedback to the controller about the current speed of the engine no matter what is the speed set by the user. The speed of the motor will equalize with the speed set by the user, but slowly which prewents this rapid change of the voltage/current. It would be great to implement the tachometer in your first circuit in order to prevent overload of the transistors when the pot shaft is rotated sharply.

    Best regards, Ivan!

    • It would be interesting to check the second circuit also, first by confirming it with an AC bulb and then reverting with the shown bridge network

      a tachometer can be avoided by simply adding a resistor/capacitor network at pin5 of IC2 which will slow down the change regardless how fast the pot or the voltage is varied

  16. So, what should those R and C be? From pin 5 capacitor and resistor in sequence to the gound? What should their values be? Does the C4 (10nF) stay at it's place in that case?
    Thanks in advance!

  17. I think I got the idea – the RC group together with BC547 works like a time-delay stage so the voltage change from the pot comes to pin 5 delayed depending on the values of R and C. That's smart!

    I need few answers:
    1. How about the power stage? Will a single MJ11022 be enough as a power stage.I am about to use a ST901T as a preamp stage and two MJ11022 as power stage.
    2. The motor voltage is 180V and the grid's voltage is 230V AC. If I use a full-wave rectifier and a smoothing capacitor the rectified voltage will be above the motor's and even transistor's allowable. The other way is to use half-wave rectifier (single diode) and a capacitor behind it in order to get smoothed voltage with the value motor needs. Should I use some bigger capacitor (the original board had a 470uF/400V one). Can I use it again? As long as I know a capacitor's capacity is determined proportional to the load's current.

    Please answer all my questions!

  18. Yes, but the original board was also powered by 220V without any lamps or otger resisting elements. Rather I was meaning that all the circuit can be set to power the motor to 180V only no matter what the grid voltage is – with other words we have 220V, but the power transistor passes only 180 of them at maximum turn of the potentiometer.

    The circuit from the link you posted is with MOSFET, there's no problem to drive it directly from the IC, but in the first circuit above power Darlington BJT's are used. I don't intend to use MOSFETs anymore.

    ""no matter how 220 v is rectified the result will be always dangerous for the lower rated motor….""

    Why?! Do half-wave and full-wave rectification give one and the same effective value of the rectified voltage?! You said in one of your posts above:

    ""The 180V could be achieved through a half wave rectification using a single 6A4 diode and filtered using a 10uF/400V capacitor.""

    Exactly that was my second question. That's why I want to get clear everything before start to build the circuit. Thanks!

    • These are PWM circuits they don't control voltage rather the RMS value… in other words it controls the average voltage by breaking the input into a calculated ON/OFF sequences, but the peak voltage always remains equal to the input, that's why it could be dangerous, initially I suggested using a single diode method considering the small difference between the motor and the mains voltage levels, but it's always good to be on the safer side and therefore the peak voltage issue must also be considered.

      whether it's a full wave or half wave, the input peak again would be equal to the supply mains input.

      a buck converter concept must be incorporated for dropping the voltage or the other short cut method would be to use a series 50 v lamp

  19. A buck converter . . . . Would you post a proper simple circuit of it for my case (which is the case of the theme at all). Embedding it into the main circuit will give it a finished look.

    Thanks in advance!

  20. And how about a buck converter with flywheel circuit, just like in the link below?

    We already have a PWM controlled power transistor, all that remains is just the flywheel circuit (a diode, inductor and a capacitor). As long as I can see it will provide directly 180V from the 230V rectified AC grid voltage in the power line. Would you provide such circuit, mr. Majumdar? Please!

    • The shown design can be used for your application…you can drive the buck transistor through any high frequency oscillator configuration

      an example circuit can be witnessed here

      just make sure that the drain of the mosfet is isolated from the R1—R5 positive line and gets separately connected with the 300 DC rectified source.

      The positive line of R1—-R5 must be connected with the above 300V DC lien through a 100k resistor and a 12V zener attached across the positive R1—R5 positive and the common ground.

      IC1 stage may be ignored and removed….D2 could be replaced with a 200 V zener diode.

  21. Thanks for the example but . . . . the transistor you mentioned in the part list is "Q1 = ANY 100V, 20AMP P-channel MOSFET". Are 100V enough for Q1 in my case?
    How about C3 (the reservoir capacitor) from the link? In the part list it is 100uF/100V one. I think in my case it should be at least 400V. And is 100uF capacity enough?

    Thanks in advance!

    • No, for your application the transistor should be 300 to 400 v rated…the filter capacitor will also need to be rated at 400 V minimum….100uF is sufficient because the filtration level is not critical for the speed control functioning.

  22. Any possibility contact you in skype or phone? or txt msg i had 3 mc2100ls rev controller for treadmill <,< is fried <,< so i gonna make one my own my motor use 130v and 10amp.

  23. I have read all those post and many picture of schematic I have Permanent Magnet DC Motor with specs of Volts 130 , AMP 10.0 . HP 2.5, RPM 4500, Rotation CW, Duty Continuous. Which of your diagram should I use to power this motor and use 10k pot to control from 0 to max and I would like a reverse on motor can DPDT switch will do? any pointer would help. Thanks for all your time.

    • you can try the first diagram for your application but you should have an access to 130V Dc for supplying the motor via the transistor bridge

      an ordinary SPDT switch will be enough for the reversal

    • My kind request to you is not to proceed with this project, you seem to be extremely new to electronics, and this project is not for the newcomers with no prior experience.

      everything is clearly shown in the diagram if you are unable to read the symbols you need to study the basics first and proceed gradually.

    • I clearly Understand the circuit is just that some symbol look different I'm working on proteus 8 and stimulating it in order to build the circuit. here a link of my half work so far. That why i'm asking the property value and which you used for the project that work and from there I cant experiment.

  24. Alright I have become more knowledgeable with symbol. I was though different symbol at my class and realize American standard symbol and Europe symbol look very different. anyway I redraw the diagram from Proteus and wanted to have you look it over and see if i'm missing anything feel free to edit it.

    Question The VCC is 15v but wasn't sure if it's DC or AC on your schematic. I'm almost done getting all parts from ebay to put it together.

    • The diagram looks OK, except the transistors in the bridge…you'll need to swap T4/T5 and T2/T3 positions. meaning T5 will move to T4 and vice versa, same with T2/T3. In other words the upper transistors should be NPN and the lower ones PNP.

      electronic circuits always work with DC, never with AC, so the 15V is DC…preferably use 12V DC.

  25. Hello Mr. Majumdar,

    I want to build this diagram for my bench lathe. Could i use it for this? On the nameplate of the lathe it says 220 Volt 800 Watt and i know that it is a DC motor. If so wat for components should i use for T2…T5 and for D2….D5?

    • Thanks for the quick reply.

      But the other diagram also includes a 12 volts dc motor and on my lathe is a 220 volt dc motor. I want to use a rectifier and a capacitor for the power supply of the motor direct from the wall outlet. If i replace Q1 for another, could i feed it directly the 220 Volt Dc? And do you have a proposal for the Q1 replacement?

    • yes you'll need to replace the 12V fet with a 500V fet….probably an IRF840 would do the job.

      The rectified positive of the 220V will need to be applied at the junction of D3 and the switch making sure that it's been first perfectly disconnected from R2 and the 12V supply line

      the negative from the rectifier will connect with the negative of the circuit.

      P1 will need to be connected with an appropriately dimensioned series resistor so that the max voltage to the motor is restricted at 220V, because the rectified voltage could be well above 300V

  26. Hello, I have build the diagram but when I turned it on the motor started to turn but I could not control it. I think it has something to do with the IRF840 I used. According to the datasheet of this it has a build in diode so it lets the DC power go straight thru in one direction. I've tried to put the power in the other way but then it blow out the other diode D3. Do you have any idea what to do?

    Kind regards

    • Hello Rookie, referring to the following circuit:

      initially don't connect the load or the 220V AC, just power the circuit with 12V and check the gate voltage while varying the pot.

      The voltage must show a corresponding 0 to 12V variation, if this does not happen would indicate either a faulty IC or connections,

      the diode inside the mosfet has nothing to do with its performance, it's there for protecting the device from transients and back EMFs.

    • Hey Swagatam,

      Excuse me for the late reply. I've checked the voltage and its varied while turning at the pot only the voltage varies between the 0.8 and 11 volts. So this part works.

      But when i start the circuit at zero, i can turn it slowly to max but it won't turn down anymore. When i've done this i have to wait a few hours then i can do the same thing again.

      Do you have any other suggestions?

      Kind regards

    • Hi Rookie, to which diagram are you referring to?? I will recommend that you build the first diagram in the above article. You can eliminate the stage that's connected after pin3 of IC2… can directly connect the mosfet gate to pin3 of IC2, then connect the load between the motor +V and the mosfet drain.

      the source of the mosfet will connect with the circuit negative.

      the +Vcc for the circuit should be applied from a 12V DC adapter.

  27. hi Ialso have a treadmill motor@130vdc @15amps Iwill be120vac with a brige for and feeding the ic with 0-18 vdc after wiring and putting in all the parts needed, my question is where dose the 130vdc come from to hook up the motor???

    • The 130v will come from your mains AC outlet after rectifying it through a bridge diode network, although it would become 150V after rectification, can still be used for a 130V motor considering the regulation feature available with the circuit.

    • it's clearly shown in the diagram, the point indicated "motor voltage" should be applied with the 130V positive, and the negative to the lower rail of the bridge….all the negative or the earth symbols must be made into a common line.

  28. ok so just connect the 130dc on the plus where the motor is connected and the – to 0 rail : I don't understand how the motor would get the pluses. thank you swagatam

    • 130 (+) to the point indicated as "motor voltage"
      the pulses are applied to the respective transistor bases.

      I am referring to the first circuit in the above article.

  29. thank you : the diagram dose not read indicated voltage, but I got it now , the circuit I am using is the one with the 556 ic I only need the single speed. thank you I will start to build it.

    • in the above article 555 IC are shown but if you wish you can use a single 556 instead of the shown two 555

      voltage is not indicated because different users may have different voltage requirements as per their motor specs.

  30. ok I will use the one with the 2 ic the motor that I will hook up is a 130dc @15amps so is there anything I need to know for the hook up ???thank you

  31. sounds good : but on ic 2 pin 3 what dose 100 mean ?? and for the mosfet the application notes points out that the drain should be connected to a positive terminal of the supply and you say the neg – ??? thank you

    • which circuit are you referring too…? I can't see anything marked as 100 in the first circuit IC2 (pin3) above……. neither there's any mosfet in this circuit…

  32. Hi Majudar,I want to construct a motor controller based on the open source design here

    I want to use the circuit to power a 180V 15A d.c motor but i don't know how to go about modifying the original circuit for this purpose.

    According to the documentation provided, the circuit can handle currents up to 160A thanks to the IRF1405 mosfet in use.

    Now, i know i have to change to a mosfet with a current rating of about 15A based on my motor specification but i dont know how to make the system operate at up to 180V. Do i also have to find a mosfet (or BJT) with more than 180V rating? The mosfet currently in use is rated 55V, 133A.

    Also, the circuit has an HIP4081A mosfet driver, please can you briefly explain how a mosfet driver works and whether this particular mosfet driver will be appropriate based on the ratings below.

    The mosfet driver is rated, High Side Voltage = 95V, supply voltage = 9.5 V ~ 15 V

    • Hi Folajimi,

      yes the mosfet rating will need to be well over 200V, and 20 amps for safe operations.

      I'll check the datasheet of the driver IC and try to update the info soon for you.

      the 180V can be derived from either a step down transformer or from an smps adapter, which may be specially designed and procured for your application.

    • Hi Majumdar,
      Thanks for the reply. It's been very helpful. I am expecting your response regarding the MOSFET driver. However, I want to add that i intend to run the motor from a 24V battery and not from mains.

      Thank you.

  33. (repeating my posting as I'm not sure it went through…) Hi Swagatam, thanks for this. I'm trying to fix my treadmill using the dimmer + bridge rectifier option you show at the end. I have a 2000W AC dimmer, a 50A 1000V bridge rectifier and a 400V 4.7uF capacitor across the DC output. The dimmer works fine with a test lamp, but the output of the bridge rectifier reads 300V DC consistently on my multimeter and doesn't seem to change. I tried connecting it to the treadmill and it blew the fuse in the dimmer and destroyed it. Not sure if I have broken the treadmill.
    Do you have any idea what I am doing wrong? Is the capacitor too big/small? Should I use a lower power bridge rectifier? Any advice or suggestions? Thanks, Nick

    • Hi Nick, I seem to have lost your previous comment, not sure how and where.

      As for the last circuit, It looks to be technically correct, however a closer inspection shows that the inclusion of the filter capacitor across the bridge rectifier could be causing the issue, please remove it and test it once again.

      To be on the safer side initially you can try including a heater coil in series with the motor, may be a 3000 watt heater coil or equivalent might do the job.

      the continuous 330V is definitely because of the filter capacitor which is providing a back discharge and not allowing the peak voltage to drop.

    • Thanks, Swagatam. I replaced the dimmer and have now removed the capacitor. I don't have a heater coil, but I connected up a 100W bulb (40 ohms) in series with the motor to avoid drawing too much current. The bulb gets brighter and dimmer and the voltage across it varies nicely from 0V to 220V, but the motor is not moving at all.
      Do you think the bulb is providing too much resistance? At 40 ohms, the max current is 4A and the motor is rated to 11A, so perhaps the motor needs more current. Or perhaps my several earlier attempts have blown the motor. Is there an easy way to tell?
      Thanks again for your help.

    • Hi Nick, the series load should be at least 3 times more powerful than the actual load, otherwise it could completely block the actual load's functioning by introducing a much higher resistance in the path….a 100 watt is definitely not the correct match for the proposed testing….it should be at least twice the wattage of the load, although I am not aware of the actual load wattage that you are using, i assume it to be much bigger than 100 watt

  34. Hello, mr.Mjumdar, I haven't been there long time ago. I finished my tests with dimmer driving of PMDC motor 8 months ago and I rate them as danger and unreliable with regard to safety and stability. Once the triac blowed up and the motor raised its RPM's to the space before the fuse interrupted the mains circuit. The idea with putting a powerful light bulb as a voltage divider is groundless because of the power it dissipates in the small area of the treadmills motor bay.

    That's why I will try with the PWM concept, no matter of his complexity, not to mention that the original development used the same technology. I hope it will work much better than the previous one.

    Best regards, Ivan

    • Hello Ivan,

      if the blowing-up of the triac was the issue, in that case you try using a bigger and a higher rated triac, and also employ a fuse in series, that would solve the issue. The important thing is that whether or not the dimmer concept works and is able to regulate the motor? If it does then I think the triac issue can be corrected by simply using a more stronger or high current triac such as BTA41/800 etc.

      The PWM option is also great but compared to the dimmer circuit ity looks much complicated and technically difficult.

      Anyway I wish you all the best!

  35. ". . . .such as BTA41/800 etc"

    It was BTA41/600 already. Besides that, the noise from the motor becomes louder when the RPM's go down. The speed cannot be adjusted from zero (at least not in my case) and is unstable. And finally, if there's a man on the treadmills belt when the problem occurs, he will fall down, with possible injury.

    Thanks for paying attention to me and my problems, will find the solution with the first circuit!
    Best regards, Ivan!

  36. Hi, mr.Majumdar, I did the first circuit. As expected, it doesn't work. I'm absolutely (120%) that it was correctly assembled. I used a light bulb as a load, because the motor is a very risky try. When the pot is at min. there's no voltage on the bulb, but when slightly opened, 207V are suddenly on it and so on until pot gets on max. With other words, there is not any stepless driving of the load – just on or off. With the scope there are pulses on the pin 3 of IC2, but it is impossible to say if their width changes or not – they are very hard to be distinguished each from other.

    • Hi Mr. Ivan, The first circuit has been tested by me not once but many number of times for different applications. This is one of the best PWM controller circuits I have ever seen, so it's beyond doubt that this circuit would surely work.

      However the design is not simple and it's recommended only for the experts in the field who has a thorough knowledge of practical and theoretical electronics.

      For the last circuit also you said the triac burnt, whereas as per the datasheet the triac is rated to handle 40 amp continuously and 200 amps in the form of short pulses, that's again extremely strange….the datasheet cannot be wrong?

  37. And what's so hard in the first circuit so I must be an expert in order to run it? The only adjustable component inside is the pot?! There were much more tricky circuits I created at once. I think it's time to show you my circuit under which I created the board. It's not absolutely the same as yours because of the single way rotation needed. I'm uploading a PCB picture too. Let me know if there's something wrong with the circuit . . . .

    The circuit:

    The board:

    • when you are not able to troubleshoot a circuit then it's complicated for you.

      a circuit is not about just building it exactly as shown, it's about knowing precisely how it's designed to function and troubleshoot the problems if anything goes wrong.

      Can you tell me how the IC1 and IC2 together become responsible to generate the PWMs in response to the pot adjustments?? and what's the function of each of the parts??

      sorry I can't verify the pics because it can be too time consuming…but I can assure you that the circuit in the first diagram is correct and has been tested by me, now it's upto you to discover the faults by checking it stage wise.

      I have explained how 555 geneartes PWMs in the following article elabprately:

  38. Mr.Majumdar as you said at the begining "Here's a SIMPLE PWM based motor speed controller circuit which can be used for controlling a treadmill speed right from zero to maximum." Your blog (which I consider very useful and interesting) is visited as you can see (at least this theme) by newcommers. If the circuit is too complicated and the people who will try to build do not have even the slightest idea of how it works and how to be checked for troubleshooting, then what is this all about? Even Mr.Samuel, the man who gave the request, did he run the circuit?

    Alright, let it be so, let's forget about this . . . . How abot slowing the on threshold of the second circuit, it's the main disadvantage of it? The output starts not from the zero but from few dozens of volts. I think that it's because of the high breakdown voltage of the BD3 diac. Can something else be used instead of diac, for example something from the MOCxxxx zero-cross series? I think it will be much more comfortable for the motor starting at 20-30rpm or even less, for example instead of, let's say, 300rpm.

    • the word "simple" was mentioned in context to the subject….compared the complexity of the PWM concept this circuit looks easy that's was I meant to say in the article..

      But even if we consider it as simple and friendly to a newcomer, so it means you could not make this simple circuit work?

      as far as guidance is concerned, I am always ready and I have always been helpful to everybody in this blog, and all have shown tremendous trust in me and my work.

      yes you can use a MOC3043 IC for driving your motor and I think it would make things much safer, however for driving the MOC you'll need a PWM feed.

  39. ". . .however for driving the MOC you'll need a PWM feed."

    That's exactly what I meaned mentioning using MOC series chip, at least it combines the advantages of both circuits, presented here.

  40. Hello sir thank you for your time and the courtesy of putting these circut designs online. I have lathe which the electronic control went bad on … its got a 250w 110 vdc motor and i want to build a circut like the first one at the top of the page to use as a speed controller. Would it be possible to build the pwm circuit excactly as shown but using a 556 timer for my purposes? secondly would it be possible to use a dpdt switch instead of the transistor h-bridge for directional control of the pwm signal or would that not work? 3rd since i plan on full bridge rectification of 110vac mains and am expecting to end up some where around 156v dc after rectification and my motor only needs 110v would i be able to use a voltage divider to create the 15v vcc input? lastly do the uf ratings of the capcitors change with the higher vaoltage needed in my circuit? Thank you for you time and your response would be greatly appreciated.

  41. do any changes have to be made to the alternative designs for my situation? especially the 2nd alternative. The auto door control design calls for a irf540 mosfet which is rated for 100v source and my motor is 110 with rectified source being around 150v will that be a problem for that mosfet? or should replace it with a m11021 transistor instead? also the design calls for ICMM74C14 can ic4049 be used intead? The circuit looks like it is for a 12v motor. please advise if there is anything else in the auto door control circuit I must change for it to work with my 250w 110v dc motor. Thank you again for your time.

    • yes the existing mosfet will need to be replaced with a different mosfet having 200V/5 amp or nearby specs

      4049 can be used for the design.

      for operating with 110V DC, you will need to isolate the DPDT connection from the R2 point and connect it with your 110V DC source….and the circuit section will need to be powered from an external 12V DC supply.

      rest all can be as is

    • Do the ic4049pins match the pins of the mm74c14? Like is 1 actually 1 and not some other pin? And Im assuming the 100kpot in the open/close door circut will be the knob I turn up and down to speedup/slowdown the motor is that correct. Also how do you suggest I isolate the dpdt switch? For some reason I was under the impression that connecting ground together from both circuits would allow high volts/current surge from the motor circuit to the controller circuit. Is that not the case? Thank you again for your time and responses.

    • Pinout matching of the two ICs is not important, you just have to use the 4049 gates in the appropriate locations as indicated in the diagram, you can refer to the datasheet of the 4049 IC for learning the details.

      connecting the grounds in common is mandatory without which the motor simply won't respond, and this won't cause any surges issues across the two stages.

    • Thanks again for your prompt responses. With the isolation of the dpdt switch to the 110v motor circuit Im assuming the mosfet at Q1 as well as the diode at d3 will also be moved to the 110v line correct? If so is the zener at z1 still needed? Or would it Also be moved to the 110v circuit? Thanks again for all your help. I have ordered everything I need to build the circuit and am waiting for arrival so I will keep you updated with how it goes. Thanks

    • Ok great.. And that reminds me i forgot to mention for the 12v circuit i recall you mentioning an smps power supply however i dont know how to tell if it is a smps powersupply or not… im using a small ac to dc (wall dart) power adapter which belonged to a wireless router enclosure. It is label rated at input: 120ac 60hz. 300ma AC and output: 12v 1a DC.. When plugged in and tested with mutimeter and no load it reads 13.67v dc and it seemed pretty constant but then again it had no load. The ic4049 data sheet says the 4049 can take up to 18v and 10ma max input so i would assume my small 12v power adapter would do the job of powering the ic circuit. But i keep worrying about the smps situation so i just wanted to ask about that. Im not sure how crucial smps was to the operation of the circuit. Thanks again.

    • I suggested an SMPS since most smps have regulated output using zener controlled feedback.

      yes 13/14V will cause no harm to the circuit although a fixed 12V is the recommended value….initially you can go ahead with your available set up, and see how it responds.

  42. Hello Good Day,
    I built this circuit for my treadmill, in AC Load (220VAC 500W) its working properly but when i connect it in 25Amp bridge type diode into the Motor my dimmer not working it continues running only but not slowing.

    I thinking about to assemble your second schematic but i am not pretty sure it will work on my treadmill motor, (220VDC 1.35KW and around 8Amp) the rating of the motor.

    Can you help me with this problem sir?
    Thank you very much.

  43. Hi Mr. Majumdar. In the second circuit, can we just use a high current dimmer + a high current rectifier? Then all I need to purchase is two entities, without going into customizing the circuit.

    Furthermore, in this circuit, will there be any loss in torque and/or excessive inrush current? Thanks.

    • Yes that's right! I am not sure about the torque issue, the dmmer will vary the average voltage level across the motor for the speed control, as per the pot operations.

      but first make sure to test the dimmer circuit with an ordinary ceiling fan or a 200 watt bulb, before setting up the bridge and the treadmill motor

  44. Dear sir, please let me know how can I run a 180v DC treadmill motor with 5400 rpm and 1.5 hp by using 220 v normal ac current in India. It would be great if I can send u pics of my motor.

    • I think it's already discussed in the above article and the comments… can preferably try the second circuit from the above article.

      make sure to use a 100K resistor in series with the pot

  45. Hi Mr. Mazumdar. Please let me know how to run a 180v dc 5400 rpm 1.5 hp motor from a threadmill with 220v ac current here in India. I'll send pictures of motor if you want to have a look. Please help me. Also let me know if this motor can be run both sides. Thank you so much for your time.

    • Hi Peter, if a capacitor is used the whole idea of PWM control would get mitigated, because adding filter capacitor would cause a constant peak voltage for the motor and stop the PWM function from controlling the motor speed.

    • Hi Peter, yes + indicates the +12V line of the circuit itself.

      the BC547 should be actually BC557, please note this.

      you can try a IRF450 for your motor application or any other similar.

  46. Hi Majumdar.
    How are you?
    I'm having a 2.5HP 180v DC Treadmill motor. I just want to make a circuit which can control its speed from zero to maximum. (No need for reverse direction)
    Please guide me through simpler circuit as I'm beginner.
    Please send me the Simulated File i.e Multisim or Proteous File if possible.
    I'll shall be very thankful to you!!
    May God bless you!

  47. Hi sir, I have a DC motor which uses electromanets where Armature Voltage is 70VDC and Field voltage is 90 VDC.
    Just help with a circuit diagram to power & regulate the speed, thanx

  48. Dear Swagatam, when i've planned to produce this unit, i have one question.
    Here in The Netherlands we have 230v, so, i can't use the MJ11021 darlington.
    The DC is going up to 300 volt, so i need to use the suggested ST901T or even the TIP151. The question is: Which PNP version do i need? Since there are only NPN versions to find. Kind Regards, Rob

    • Hi Rob, I tried to search for a 350V/400V 5/7 amp PNP Darlington transistor but strangely I could not find a single appropriate one. I'll do some more search and let you know soon if I happen to find one….if finally we are unable to find any, we can go for non-Darlington PNP BJTs with a supporting smaller PNP and configure the two like a Darlington

      Alternatively you can also try Mosfets in place of BJTs and that would work equally good, according to me.

  49. Thanks for the fast reply, the problem with me is that i'm not a designer. I can build things from a diagram and fix problems when a part is broken. For me it's too risky to experiment with this high voltages. I hope that you know the right solution for me… Your layout is still the best looking option of all diagrams i could find. Thanks a lot!

    • OK, for the PNP you could probably use MJE5852 and 2SAR340P together to form a 400V rated Darlington transistor, the configuration is simple and may e done as follows:

      connect the emitter of the 2SAR with the base of MJE, connect their collectors together,

      that's it, the darlington pair is ready.

      use the collectors as a single collector, the base of 2SAR as the base, and emitter of MJE as the emitter for the final connection in the circuit.

      I hope you got it.

  50. The 2SAR340P is a very rare transistor… Can't find a shop in the world to buy it. Is there a more common version? Thanks again!

  51. Dear Swagatam. I have a problem on the kind of project, i would really appreciate any assistance. I’m controlling a 180Vdc, 0.25kW PMDC motor using bluetooth, thus I can’t use 555 timer. I have been planning to use Arduino UNO, the problem is finding the relevant H-bridge driver since the PWM from the arduino is about 5V. Thanks in advance.

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