Suppressing Motor Noise

Discussion in 'The Projects Forum' started by cas0586, Sep 12, 2014.

  1. cas0586

    Thread Starter New Member

    Aug 12, 2014
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    I have been working on a battery operated ride on project using an ESC and custom microcontroller to act as PCM and have come across the first real issue. The issue is noise from the electric motors.

    I am using an MSP430G2452 MCU and the input voltage regulator is an LM1117 with a 10uF tantalum cap on the input and output per datasheet.

    When the throttle is pressed part throttle the tail lights flicker madly. At full throttle it smoothed out. The front park lamps do NOT flicker. Which leads me to believe the tail lights being more near the motors are picking the interference up through wires and this is not a voltage regulator cap issue.

    I would love to solve this issue and look forward to your suggestions. If you need any more info please let me know and I will try to provide said info.

    Thanks!

    - Sall
     
  2. #12

    Expert

    Nov 30, 2010
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    A drawing of the circuit and the wiring always helps...or we're just trying to read your mind about how this is hooked up.
    I mean, smart guesses are still guesses. Give us something to work with.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
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  4. cas0586

    Thread Starter New Member

    Aug 12, 2014
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    Here are the schematics for the ride on. I believe it be accurate. Vreg/mcu power simplified.

    [​IMG]

    S1 - SPST Ignition Key Switch
    S2 - Park/Tail Lamp Switch
    S3 - Brake Switch(Pedal)
    S4 - Reverse Switch(Shifter)
    S5 - HeadLamps Switch
    S6 - Emergency Switch

    P2.0 - Left Tail Lamp
    P2.1 - Right Tail Lamp
    P2.2 - Left Reverse Lamp
    P2.3 - Right Reverse Lamp
    P2.4 - Headlamps
    P2.5 - ESC Power/Ignition Relay Trigger
    P2.6 - Left Park Lamp
    P2.7 - Right Park Lamp

    [​IMG]

    S1 - 'Park'/Reset Switch(Factory Apache Reverse Switch in Shifter Assmebly)
    S2 - Reverse Switch (Factory Apache Drive Switch in Shifter Assembly)
    S3 - Brake Pedal Switch

    RY1 - Motor Reverse Relay
    RY2 - Motor Brake Relay

    I removed the motors and added a 0.1uF cap tonight from each lead to motor casing and one between each motor terminal with no improvement.

    I'm not sure that applies ScottWang as I am pulling 12v from one battery that is inseries with 24v to power MCU? Please advise. Thanks for any input!
     
    Last edited: Sep 13, 2014
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,526
    2,369
    I see an absence of caps, both electrolytic and 0.1's.
    Is this on purpose? as it would be and idea to show what you have in the circuit.
    Max.
     
  6. cas0586

    Thread Starter New Member

    Aug 12, 2014
    12
    0
    The diagram was simplified. Per datasheet 10uf tantalum on vreg input and output. The caps on the motors were just added tonight. 0.1uF from each lead to motor case and one between motor leads. Hope that helps.

    I also just tried the 5ohm in series with 470uF cap parallel to MCU supply and no saw no change.

    I will try to update diagrams tomorrow to reflect the changes thus far mentioned above.

    Anyone else care to take a stab?
     
    Last edited by a moderator: Sep 15, 2014
  7. #12

    Expert

    Nov 30, 2010
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    6,789
    I think it unlikely that you can induce enough current in a nearby wire to light up the tail lights, so I'm going for interference from the controller getting back to the MCU. In the first drawing, I see a shared ground wire at S1, Vreg, and YK31C. I'd start there with extra wire to make a single point ground, then think about ceramic capacitors of 1 nf to suppress high frequency noise. Aluminum electrolytics don't work so well at high frequencies so you end up putting a .1 uf cap in parallel with the electrolytics.

    This can be a gigantic pain if you've already wired everything up without an awareness shared ground wires and how current pulses can rattle the ground voltage at the MCU all over the place. Of course you know about keeping the 3.3V to the MCU clean, but this is the other end of the same stick.
     
  8. cas0586

    Thread Starter New Member

    Aug 12, 2014
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    Thanks for the response #12. The tail lamps do not come on on their own when the throttle is pressed. I have set the MCU up so when the ignition is keyed on the parks and tails are on reduced intensity(pwm). When at part throttle the tails flicker. The only lamps that flicker are the tails not the front parks. I guess I do not understand why it would effect only the tail lights if the interference was getting back to the MCU?



    Apparently I drew that wrong as the ESC(YK31C) is actually grounded directly to the battery. I am still a novice, but do my best to understand!
     
    Last edited: Sep 13, 2014
  9. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    If you could separated the power of mcu from motor, and to make sure where was the noise came from, if you have the O'scope then you can measure it to find out.

    Different noise using different solution.
     
  10. cas0586

    Thread Starter New Member

    Aug 12, 2014
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    I don't have an o-scope.

    What do you mean separate the power? The MCU power is 12v from one of the batteries. The motor gets power from the ESC via both batteries in series.
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,783
    944
    Please provide details about the wire routing. Specific to motor power leads and power leads to any mis-behaving light assy.

    Do they run together in any type of harness or perhaps just at a single point? Try separating the wiring if so.
     
  12. cas0586

    Thread Starter New Member

    Aug 12, 2014
    12
    0
    Seems this is working as a fix. Down side is uses more current keeping the relay coils latched until groundis broken by switch.
    Noise-Fix.png

    Had to do this for the brake and reverse relays. A few wire swaps and an additional wire for respective MCU inputs.

    If I have any other issues I will report back. Thanks for the help!
     
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