Relay question

You would wire the coil between the insulated rail and the center rail (or independent supply hot side).  When a train rolls over it, it will complete the circuit to common and pick up the relay.

Which MTH block signal are we talking about?  We use the PRR 7-light ones on our modular club layout, that just needs a switched lead and continuous power.

Here's the instructions for that signal: http://www.mthtrains.com/sites...ction/30as14381i.pdf

If you have the make and model number you can google it and likely find the manufactuer's data sheet.

This will give you all the specs plus the wiring diagram.

Most decent relays have the wiring diagram printed right on the case as well.

What voltage is the coil rated at. You said its AC. Is it 12 VAC, or?

Rod

Gunner, the block signal is similar to the PRR one but the 3 color version.  Rod, the relay is rated at 24v AC nominal.  The problem is I have very little knowledge of how to interpret the diagram so it has been trial and error.  I have created some remarkable sparks by the way.  It's one of those things that once you learn it you wonder why it didn't make sense in the first place but I have not arrived at that destination yet.  I have the cantilevered signal working off of the z stuff relay and that is working just fine.  Wonderful little product.  Just don't have any more at home and thought I would try this thing.

Gunner, I stand corrected, the block signal I have has 3 wires, not 4 as indicated in the link you provided.  There is a green, red and black wire.  Green and black lights up the amber then green sequence.  Red and black lights up the red signal.  

Well, first off, the 24 volt may be marginal on a lower voltage as it typical for accessories, so you need to verify for the voltage you'll be driving it with, it'll reliably close.

For this relay, the black will go to common of the track, Red would go to the N/O contact, and Green would go to the N/C contact.  Power would be wired to the arm of the relay contacts to activate whichever signal that's appropriate for the conditions.

I obviously can't tell you the exact pins without knowing the exact relay you have.

18 VAC will work a 24 VAC coil usually. If you run it off track power add a TVS across the coil for spike suppression. Directions are here for a DC relay,just dont use the bridge and capacitor. You could also run it on DC as shown in the below link. Usually there is a diagram on the dust cover. If not look at it and you will see the internal wiring. The coil leads would have about 200 ohms resistance between them if you use an ohm meter..

http://www.jcstudiosinc.com/BlogShowThread?id=410

Dale H

Well thank you all for the advice.  The diagram was a great help.  For the life of me I could not figure out why it would not work UNTIL I turned up the voltage.  It appears I purchased an item that was rated too high.  Without being able to measure the voltage going through the wires I am guessing but the throttle on the test bench out of a Z-500 was well over 3/4.  I will retest this on a 14V fixed line on the layout but do not expect good results.  Live and learn.  The purpose of the question was to learn how to wire and that was accomplished. 

I believe the relay that would work better would be the Magnacraft W88ACPX-6. DPDT 12VAC coil . The attached picture shows them from an installation years back.

Assuming it is a 24VAC coil if you use 14 volts AC with a bridge and capacitor you will get 20 volts DC,that should work the coil.

Dale H