Anything 1 amp or more,35 volt or more
example
www.radioshack.com/product/ind...p?productId=12678416
For a capacitor 470 uf 35 volt is fine and usually is sufficient to eliminate chatter
If a separate transformer is used one of the DC poles (+ or -) can share a common and only one bridge is needed regardless of the number of relays used as long as the bridge rectifier and transformer can handle the amperage of all the relays. I use hundreds of relays on my layout.
You can run your AC relays on DC. Cut the input voltage down until it just works and then add a few volts. The AC coil will have less resistance on DC and need less voltage. Too much can damage the coil.
Dale H
