cap size for relay

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=117820
Printed Date: May 14, 2025 at 8:39 PM

Topic: cap size for relay

Posted By: rtm038
Subject: cap size for relay
Date Posted: November 17, 2009 at 11:41 PM

Hello,
After reading a few other posts about adding a capacitor to the coil of a relay that is being controlled by a fading interior dome light in order to eliminate “chatter”, I gave it a try using a 470uF 50V capacitor and it worked perfectly. However, the actual size (dimensionally speaking) of the capacitor is pretty big. Is there a smaller size capacitor I could use instead? The relay is standard 12+vdc Bosch style automotive relay and the capacitor may only have a few seconds to charge up before the interior lights begin to fade out.

Thanks
Ryan

Replies:

Posted By: Ween
Date Posted: November 18, 2009 at 5:44 AM

hi,

try using a 16 volt or 25 volt instead. and look for a capacitor rated at 105 deg C instead of the usual 85 deg...for longevity. also if you look into other relays with lower coil currents, your capacitor values/sizes should also be reduced.

Posted By: i am an idiot
Date Posted: November 18, 2009 at 6:20 AM

Also try a 220Mic capacitor. It too should work.

Posted By: keep_hope_alive
Date Posted: November 18, 2009 at 5:50 PM

tantilum capacitors are much smaller than electrolytic.

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