Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Conscripted on March 29, 2011, 06:58:47 AM

Title: Purpose for capacitors soldered to case of DC motors?
Post by: Conscripted on March 29, 2011, 06:58:47 AM
Good morning all.

I was surfing about the internet looking at robotics projects other people have done and came across one or two mentions to putting ceramic capacitors between the leads of small DC motors and possibly also between each lead and the metal case.

What is the purpose for this? Are the capacitors there to absorb the back EMF? Is this as a replacement to protective diodes?

I don't think it's all crap because I know I've seen this done on a few of the commercial products I've torn apart over the years.

Thanks for any information.
Conscripted
Title: Re: Purpose for capacitors soldered to case of DC motors?
Post by: waltr on March 29, 2011, 07:56:39 AM
The caps are to suppress high frequency noise and hash. This is mostly from the commuter brushes making and breaking contact and therefore arcing.

Take a look with an O'scope on an unsuppressed motor terminals. Or put a pocket AM broadcast radio receiver near the motor.