Need Help in Noise Reduction in Brushed 775 Motor.

Discussion in 'General Electronics Chat' started by evansourav, Jul 18, 2018.

  1. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Hello Everyone, I am new to the forum so please bear with me if I am writing this in the wrong section, Dear Admin Please move it to the right section if necessary.

    So I am using a 35Watt (12v SMPS) 775 DC Brushed Motor with PWM Motor control board, i am using 4700Mfd capacitor in parallel and 3 0.1 uf ceramic caps but there is so much electrical noise that I can't hear anything on my radio :mad:, I am a radio lover and I am not able to find a solution, can someone help me with any idea, what can I do to reduce the noise completely, or anything that I can add to my radio to remove the noise.
    Thanks in advance
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Is this a mains fed radio, or portable?
    Is the PWM controller an off the shelf unit?
    Max.
     
  3. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Hi Max Thanks for Replying
    Radio is Battery Operated not Connected with Mains or AC anyway.
    Yes it's off the shelf unit (Commercial) when I move the speed down to zero the noise becomes very low, I believe the sparks in the motor coil is the problem (Need ur expert advice though)
    One More thing use LED Tube Light this also makes a lot of noise so much so that I can't hear anything except hisssss....
    the Problem mostly Affects FM, not MW and SW.
     
  4. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    That's quite a statement about the FM and MW and SW bands. Do you have a SDR dongle? Can you see the noise on SDR dongle display?

    If you aren't familiar with the SDR dongle and decide to buy one.....get one that can receive the MW and SW bands.....they are only a few dollars more.
     
  5. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Thanks for the reply But I can hear SW and MW both almost clearly even when the motor is on, The problem is with the FM Which I can't listen to
     
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    How long are the wires from control board to motor? Are the wires shielded or twisted?

    Do you have any experience or knowledge of electronics?

    What kind of work/function is the motor doing?
     
  7. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Controll Board to Motor is 1.2 meters, twisted but not shilded (used shielded in past didn't helped)
    Motor a a simple fan.
     
  8. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    There are a couple of things you can do to narrow this problem.

    try different lengths of motor cables.

    replace twisted pair with shielded cable. Connect shield on control board only.....leave motor end of shield open.

    Then try motor shield connected only....control board open. perhaps alternate shield terminations.

    check for function of low pass filter on control board. check output with scope and fft.

    an FM trap or snubber on motor cables.

    an all band SDR dongle is great for seeing the interference. 20 bucks. AND a great all band radio receiver with fft.

    GREAT TEST INSTRUMENT.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Try running the motor direct with no PWM and see if there is any interference.
    This will confirm if brush noise is the problem.
    Max.
     
    BR-549 likes this.
  10. oz93666

    Senior Member

    Sep 7, 2010
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    off subject a little.... it's a great mystery to me why we are still using brushed motors .. they are from the stone age , yet are still widely used in DIY electric screwdrivers , drills and a thousand other items ... brushless motors are better from every possible angle.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Such as Vacuum cleaners etc still use brushed (series) motor because it is a cheap way to achieve the high (20k) rpm required.
    Brushless ECM motors are now seen in HVAC blowers etc that replace the traditional Induction motor.
    There are pro's and con's for each.
    Cost also comes into it.
    Max.
     
  12. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Tested it already Brush Noise is the actual problem here
     
  13. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    Because I simply can't find and brushless motor in that price segment + power. Autally it saves me a lot of power practically than using a 220/110v fan.
     
  14. evansourav

    Thread Starter New Member

    Jul 18, 2018
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    I will test out with the cables and reply, I am specifically noticing the slower the motor rotates the lower the noise, can you please point out how can I use a snubber?
    This is the Control Board that I am using, please check. Point to note noise is getting generated with and without this unit, If there is anything that I can modify to stop the noise will be helpful.
     
    Last edited: Jul 19, 2018
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