Capacitor across motor leads

Discussion in 'The Projects Forum' started by cheddy, Dec 15, 2007.

  1. cheddy

    Thread Starter Active Member

    Oct 19, 2007
    Hello. I am disassembling a small RF controlled toy car. I'm down to examining the circuity now and there are two motors inside the toy. I see both motors have 100nF capacitors across the negative and positive leads of the motor.

    I understand that capacitors are open for DC and the motors are only ON or OFF so can somebody explain to me why they are there?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    they are there to provide a low impedance path for the sparks occurring on the brushes, so the RC control channel isn't swamped by the noise.. They're just a short-circuit path for the spark energy.