Snubber Circuit

Discussion in 'The Projects Forum' started by seascan, Aug 29, 2010.

  1. seascan

    Thread Starter New Member

    Aug 28, 2010
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    Any ideas on how ot implement a snubber circuit on a DC motor that is controlled by two relays (so the direction can be reversed)?

    (Circuit Attached)

    Thank you.

    [​IMG]
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    201
    Back to back zener diodes just above the operating voltage of the motor. I'd also put caps across the diodes and the motor itself.

    This will take care of higher voltage transients, what exactly are you trying to filter out?
     
  3. seascan

    Thread Starter New Member

    Aug 28, 2010
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  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Back to back simply means connecting the two anodes (or cathodes) of the zener diodes together then attaching the remaining loose leads across the motor.
     
  5. seascan

    Thread Starter New Member

    Aug 28, 2010
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    What is the effect from doing this... what do the back to back zener diodes do?
     
  6. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    It helps to limit the amplitude of spikes/noise created by the motor. With babck to back zeners it will be limited to the zener voltage of the reverse biased diode plus the forward voltage if the forward biased diode. eg. 12V zener will limit the voltage to 12V plus 0.7V of the forward biased diode.
     
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I'd also suggest putting a capacitor across the motor terminals, it might help catch a little of the hash that DC motors often create.

    Anything between 0.01uF - 1 uF would be fine so long as it's rated at or preferrably somewhere above the operating voltage of the motor.

    In all this I've forgotten to ask - are you having a serious noise problem, something minor or some unexpected operation?
     
  8. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    With regards to capacitor voltages it is a good rule of thumb to go for a voltage double what you are using for a supply.

    I think this thread is linked to his EMI on USB thread.
     
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