Hi there,
I have an older MTH Railking Signal bridge that has been static display since I got it. Recently I've started trying to come up with a way to make it operate. Although I've read some others wiring diagrams I figured I'd try my own using a standard 5 pin relay out of an automobile. I'm curious if anyone has tried a system like this and if it works? Apologies for the crude photo I'm no artist.
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Conventional or command?
What transformer(s) do you have?
By automotive relay do you mean 12V DC coil?
I assume you want Red signal on when occupied (Green on when vacant?
I'm running TMCC, Using a 180 watt powerhouse for my outbound track and a vintage ZW for my inner loop, Yeah one of those relays, and green when vacant and red when occupied.
Your automotive relay works "best" when 12V DC is applied to its coil to turn it on. As drawn, when a train is on the insulated-section, you will be applying 18V AC (from your Powerhouse) to the relay coil. This is frowned upon.
Additionally, when a relay is "off" (no power to coil), the relay's COM is connected to NC. When relay is "on" (power to coil), the relay's COM is connected to NO. As drawn, the Red would be on when vacant, Green would be on when occupied. Hence my question.
You have several options. Here's my suggestion. Other's can advocate a different option.
Since it's a 12V DC relay, provide a 12V DC power source. By tying the "-" side of the 12V DC source to the AC "-", this will complete the relay coil circuit when the insulated section is occupied. The 12V DC source should be from a 12V DC wall-wart. These are inexpensive; most have a coaxial-barrel style connector but you can buy a screw-terminal adapter so you don't have to splice the power cable.
Gee, at the risk of being simple and straightforward, why don't you just try something that is known to work. This is courtesy of Dave Hikel. I've done this for each signal head on the MTH PRR signal bridge.
George
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