I am planning a conventional layout with isolated track and 10A 12V relays for block control and wondering if I should use relays with AC or DC coils. I will have 2 loops with 3 blocks each, so will need 6 relays. Something along the lines of: http://www.toytrainrevue.com/block-relay.htm
www.jcstudiosinc.com used to have a lot of good information, but it seems to be offline. Does anyone know if that site is archived somewhere or will be coming back online?
I read somewhere (http://ctt.trains.com/~/media/...lation/cttpdf005.pdf) that AC relays are convenient but hard to find, but I don't think this is true now (maybe it was true in the days when your local Radio Shack store was the easiest place to get a relay). I have never used a relay before and have some random thoughts and questions:
AC relays would be convenient because I won't need a rectifier for each relay. Rectifier cost is negligible but it would be nice to keep the wiring simpler.
Every relay data sheet I've looked at says max (continuous?) coil voltage is 110% of nominal, which would be 13.2V. Am I likely to harm a 12V AC relay if I just use a 14V accessory output directly?
If 14V will harm the relay, I could just use some paired diodes to decrease the voltage (assuming the very short "dead spots" at the zero crossings of the waveform from the diode drop won't matter -- seems like if you can run a DC relay straight from a rectifier this is a relatively minor indignity). Would only need one set of diodes for all of the isolated track blocks rather than 1 rectifier per relay.
Will relay chatter be a problem from wheel/track contact? I can't add a capacitor to an AC relay to reduce chatter. Things I've read about using DC relays + rectifiers don't say anything about capacitors, but it's always an option with DC relays if it becomes necessary.
Are relays a commodity item, or is it important to get a "good brand" (don't worry, I won't buy the clearly fake very cheap Omrons for sale on a certain auction site)?
Thanks for any advice!