Chattering Relay

[nickelplater]

I have wired a Right-of-Way, 7-light signal to a relay activated by an isolated ground rail.  I am not getting a positive transfer of the ground from the active rail to the isolated rail by a passing railcar.  The relay chatters and of course the signal lights go crazy.  I have used many types of cars and locomotives to pass this ground to the relay without success.  The rails are clean, believe me.  I believe I need a capacitor on the relay coil to keep the relay closed.  I tried a 270 microfared, (only one I had on hand)  but with no help.  Would anyone know what size capacitor range would help with this problem?  Or, what other solution would you offer to keep the relay closed once activated..

Thanks,  Rick Gispanski

[lionelsoni]

A capacitor will not help unless you are using a DC voltage supply for the coil or drive the coil through a rectifier.  In either case, the initial operation of the relay will involve a big current spike as the capacitor charges.  There are ways to get around this, if you're still interested.

[steve24944]

I have several blocks on my layout for signals.

  I run a wire from the control rail to one side of the AC on a bridge rectifier, the other AC lead on the Bridge Rectifier is wired to my 18 volt accessory voltage,  then from the DC side of the Bridge Rectifier run wires to the contacts for the relay coil.  I have used a 1.4A, 100V Full-Wave Bridge Rectifier and  a 25A, 50V Full-Wave Bridge Rectifier, both from Radio shack.

Between the bridge rectifier and the relay I have a capacitor linking the 2 wires to the relay.  I have used both 1000uF 35v and a 4700uF 35V capacitor, also from radio shack.   The relay does not chatter - and the capacitor holds the relay closed for about 1-2 seconds after the train wheels clear the control rail.   This has worked quite well for me.

Steve