Motor Noise Suppression

Motors are electrically noisy. Good motor noise suppression will improve system reliability by reducing the chance of MOSFET latch up and failure [more details here].

Some things that should be considered are;

  1. Make sure your motor has a suppression capacitor fitted. A small ceramic capacitor 10nF / 100v is often fitted internally across the motor brushes. If your motor does not already have one, fit one externally across the motor connections as near to the motor as possible. There’s more information on this subject in the page Radio Controlled Machines: General wiring hints
  2. Twist the motor leads together if possible [this stops them acting like a loop aerial].
  3. Twist the battery leads together if possible.
  4. Fit ferrite rings to the motor leads.
  5. If your motor is subject to shock loads or fast acceleration / deceleration [such as in Robot Wars] consider fitting a fast acting varistor transient suppressor across the motor terminals as well.  This Littlefuse page give more information on these.
  6. Keep the motor clean, dust and metallic particles around the brushes will increase wear, sparking, and electrical noise.
  7. Make sure that the brushes and armature do not become too worn. Brushes that are worn will have a light spring pressure which will lead to more sparking which is very electrically noisy.
  8. See this article on good wiring practise.
    motor noise suppression
    Noise suppression fitted to one of our test rigs