Sunday, May 6, 2012

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.


141 comments:

  1. hi Swuag ,could you tell me

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

    ReplyDelete
    Replies
    1. Hi,

      Use an N-channel mosfet, having matching current with the load.

      Delete
  2. hi..can you give what type of motor specifications used here(ratings)??

    ReplyDelete
    Replies
    1. Any type of DC motor rated at 12VDC will do, the mosfet may be selected as per the current of the motor.

      Delete
  3. 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.

    ReplyDelete
    Replies
    1. Hi JR,

      You may connect the second motor parallel to the existing motor, however the speed control will be identical for the both the motors.

      Delete
    2. Hi Mr Swagatam, thanks for the explanation, that cleared my doubt.

      Delete
  4. 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.

    ReplyDelete
    Replies
    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.

      Delete
  5. hi,can I use it on a 24V DC motor?

    ReplyDelete
    Replies
    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.

      Delete
  6. hay Swagatam can i use the IRF1405PBF mosfet with this circuit?

    ReplyDelete
    Replies
    1. Hey Louis,

      All types of mosfets will work provided it's connected correctly.

      Delete
  7. 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.
    Thanks
    RVJ

    ReplyDelete
  8. 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
    RVJ

    ReplyDelete
    Replies
    1. Hi RVJ,

      What kind of circuit are you looking for, is it for controlling the speed of the motor or just for driving it directly at 36V??

      Regards.

      Delete
    2. It is for controlling the speed of the motor.

      Delete
    3. You can use the circuit presented in this article. Connect 36 volt to the motor wire, while provide a regulated 12V to the IC separately.

      Delete
    4. 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?
      RVJ

      Delete
    5. Hi Ravees,
      That's great, yes you can do it very simply....

      Delete
    6. 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?

      Delete
    7. 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.

      Delete
    8. 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?

      Delete
    9. 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 5x3 inches/3mm aluminum piece as the heatsink.

      Delete
    10. 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.

      Delete
    11. Dear Ravees,

      Thanks!

      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.

      Delete
    12. Is this a ceramic capacitor?

      Delete
    13. 470uF/25V is based on the motor/mosfet rating? In my case it is a 36V motor, so is this fine?

      Delete
    14. Oh... then it should be a 470uF/50V

      Delete
    15. 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?

      Delete
    16. No I am afraid 5K will not work, it has to be a 100K cariable resistor

      Delete
    17. 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?

      Delete
    18. 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.

      Delete
  9. Hi Swagatam i need pwm circuit with 15amps 12volt
    pls help me

    ReplyDelete
    Replies
    1. Hi Thameem,

      You may use the circuit provided in the above article, it will handle 15 Amps.

      Delete
    2. 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

      Delete
    3. 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.

      Delete
  10. Would this work for my 90v 15a treadmill motor? Doubt I'd use the entire 2HP with it installed on my wood lathe. Likely 1000W or under. Thanks for all your great info!

    ReplyDelete
    Replies
    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.

      Delete
  11. 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.

    ReplyDelete
    Replies
    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.

      Regards.

      Delete
  12. 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.

    ReplyDelete
    Replies
    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.

      Delete
  13. hi sir ... sir can i replace mosfet with traic because i want to control ac motor

    ReplyDelete
    Replies
    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...

      Delete
  14. hi can i replace 2n3904 switching transistor, will it increase the speed of 3v motor?

    ReplyDelete
  15. hi bro,can i use this circuit for conveyor belt....

    ReplyDelete
    Replies
    1. if it's a DC motor then you may use it...

      Delete
  16. Hi Mr. Swagatam,

    if let say this circuit can only give out constant speed instead of controlled speed, what is the possible causes to this problem? Mind to share your opinion?

    ReplyDelete
    Replies
    1. Hi Kingkiller,

      you will need to operate the shown pot for getting the required speed control over the motor.

      Delete
  17. 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?

    ReplyDelete
    Replies
    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.

      Delete
  18. 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
    Tried

    ReplyDelete
    Replies
    1. try reducing the value of the pot to 10K and check.

      Delete
  19. 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

    ReplyDelete
    Replies
    1. OK, try replacing the above configuration with the one shown in the following link:

      http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-build-simple-pwm-controlled-dc.html

      I think this will work as expected.

      Delete
  20. Hallo Swag
    That link seems to get me back to this page?
    Regards TRID

    ReplyDelete
    Replies
    1. Hi Trid,

      The above link is working correctly, it will take you to a PWM controlled DC cell phone charger design, please check it out again.

      Delete
  21. 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.

    Cheers,
    DocRoberts

    ReplyDelete
    Replies
    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.

      Regards.

      Delete
  22. 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.

    Cheers
    Rob

    ReplyDelete
    Replies
    1. Hello Rob,

      Thanks!

      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.

      Regards.

      Delete
    2. Thanks Swagatam for the help and the quick response.

      Rob

      Delete
  23. hi, low rpm also high torque?

    ReplyDelete
  24. Swagatam, i love this circuit, but is there a way i can control the motor's speed with a 0-5volt input signal?

    ReplyDelete
    Replies
    1. Hi Damon, the circuit is not designed to receive external signals, however it would work with 5V supply voltage for sure.

      Delete
  25. 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

    ReplyDelete
    Replies
    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.

      Delete
    2. what kind of mosfet should I purchase ? thanks

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

      Delete
    4. n-channel, rated higher than your motor Voltage and Current specs

      Delete
  26. 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.

    ReplyDelete
    Replies
    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.

      Delete
  27. 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 (http://s10.postimg.org/7da0t1c6h/2013_07_16_02_25_04.jpg)

    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.

    Regards,
    MD

    ReplyDelete
    Replies
    1. The motor maximum RPM will be as per it's rated specification, it cannot be increased beyond that.

      A speed controller will only reduce the RPM from the specified high value to the lower levels.

      Anyway, you may try the circuit given at the bottom of this page:

      http://homemadecircuitsandschematics.blogspot.in/2011/12/constant-torque-dc-motor-speed.html

      Delete
  28. 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

    ReplyDelete
  29. Could you use a 50k pot instead with out changing any other components? Thanks

    ReplyDelete
  30. Replies
    1. For confirmed results the cap C1 may be replaced with a 0.01uF if a 50k pot is used. rest will remain as is.

      Delete
    2. correction: 50k pot will not need any mods in the circuit....

      Delete
  31. you sir are very cool, it gives me joy seeing when peeople share their talents! YOU ROCK SIR!

    ReplyDelete
  32. 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 :D Cheers and thanks again!

    ReplyDelete
  33. 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 :)

    ReplyDelete
    Replies
    1. I couldn't understand the relation between heatsink mounting and motor positive connection.

      Delete
  34. 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 :D

    ReplyDelete
    Replies
    1. for zero to 100% speed control you will have to make the following circuit, the above circuit will not provide 100% control:

      http://4.bp.blogspot.com/-G-E1CvLaU4U/UOfhAH6C0ZI/AAAAAAAACas/nsaEsevlY6k/s1600/reverse%20forward%20dc%20motor%20speed%20controller%20circuit.jpg

      Delete
  35. 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.

    ReplyDelete
    Replies
    1. Thanks Buddy:) appreciate your enthusiasm!

      The 100% constant torque would be a better option as it presents more efficient PWM control over the motor, here's the article which are to referring:

      http://homemadecircuitsandschematics.blogspot.in/2011/12/constant-torque-dc-motor-speed.html

      Regards!

      Delete
  36. 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)

    ReplyDelete
    Replies
    1. Thanks JC,

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

      http://1.bp.blogspot.com/-jONLYQ8Ehro/UkD_gzAjA-I/AAAAAAAAFSk/nt6vxMDF9RU/s1600/ELC%20circuit.png

      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.

      Delete
  37. 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!

    ReplyDelete
    Replies
    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:)

      Delete
  38. 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.

    ReplyDelete
    Replies
    1. use IRF540 mosfet and 15amp power supply, this will drive the motor with the specified power.

      Delete
    2. 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?

      Delete
    3. Connect the mosfet leads in parallel, use separate resistors for the gates.

      And do not short circuit the positive with drain, this will instantly blow off the mosfets.

      Delete
    4. 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?

      Delete
    5. In the diagram no resistor is indicated, but you can use 100ohms with the gates, will be OK.
      4amp will not give you 15amp....you will need a 15amp supply for that.

      Delete
  39. 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 ?

    ReplyDelete
    Replies
    1. the pot control is for speed control, it has no relation with current....use a 2amp fixed current power-supply for getting the required current restriction.

      Delete
  40. Hello sir,
    Can this pwm circuit provide exactly 2A current ? and how?

    ReplyDelete
  41. 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?

    ReplyDelete
    Replies
    1. No it's only from 50% to 100%, and frequency will not be constant if duty cycle is changed for this circuit.

      Delete
  42. 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?

    ReplyDelete
  43. 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.

    ReplyDelete
    Replies
    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??

      Delete
    2. mosfet may not be necessary, you can use a TIP122 in its place and connect the motor as indicated (across collector and positive)

      Delete
  44. hi,
    what power supply and mosfet should i use for a 180 to 220vdc motor, as well as adisplay in the circuit to show the motor rpm

    ReplyDelete
    Replies
    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.

      Delete
  45. Sir can i use two Motor in parallel

    ReplyDelete
    Replies
    1. yes you can do it if the total amp is within the max rating of the mosfet

      Delete
  46. 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

    ReplyDelete
    Replies
    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.

      Delete
    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

      Delete
    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.

      Delete
    4. Dear Sir,

      Thank you for your mail...

      Sir, then I have to connect Ground of 180V DC supply to Drain pin of MOFSET. Am I right sir?

      Regards,
      Shine K P

      Delete
    5. 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

      Delete
    6. Dear sir,

      Sorry.....

      Now I understood....

      Thank you very much...

      Regards,
      Shine K P

      Delete
    7. Sorry sir...it was my mistake......

      Delete
    8. 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

      Delete
    9. 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.,

      Delete
    10. 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

      Delete
    11. 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.

      Delete
    12. 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.

      Regards,
      Shine K P

      Delete
    13. 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

      Delete
    14. 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?

      Regards,
      Shine K P

      Delete
    15. 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

      Delete
    16. Dear Sir,

      Thanks....Let me try...

      Regards,
      Shine K P

      Delete
    17. 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?

      Regards,
      Shine K P

      Delete
    18. Dear Shine, which mosfet have you used? Please confirm if those are adequately rated as per the load.

      Delete
    19. Dear Sir,

      As you suggested, I used IRF 840. My DC motor is 180V 6Amps.

      Regards,
      Shine K P

      Delete
    20. 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

      Delete
  47. 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

    ReplyDelete
    Replies
    1. Dear Lokesh,
      If possible I'll try to design the required circuit and post it soon in this blog.

      Delete

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.


Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.