wiring/relay think-through

[HopperSJ]

I hope I can explain this scenario more clearly than I was able to state my subject! I am hoping you folks can help me think through my wiring situation.

I have a small layout (6x8) with three road crossings. I have installed a signal at each crossing and have one crossing bell sound machine. My intention is to make each signal flash individually when the train goes by. So far, so good. This is easy. However, I want the bells to ring whenever ANY of the crossings flash. I plan on hooking the signals and bells up to aux power.

Initially, I was planning on using SPST relays. (When a train passes the crossing, an insolated rail triggers a relay that in turn triggers the signal/bell) However, it is my belief that if I use a SPST relay and just hook both the signal and the bell to the output, and then hook each of the relay outputs for the bell to the bell, then when one signal flashed they all would flash (because the current from one crossing would trigger it's relay, then send power to the bell, where it would be wired into the output from the other relays, which are all connected to their own flashers and therefore all the flashers would flash?).

I then decided I could use DPDT relays. I could set it up as stated above except for one difference. Using a DP relay allows me to have separate outputs. If I hooked Aux power to input on both poles and had one pole output going to the signal and the other pole output going to the bell then the when the current reached the bell it would not travel back to the other signals because they would be isolated by the relay (because they are attached to the other pole). This way, of course, would leave one "throw" vacant which would act as the "off" for both poles.

OK, does your brain hurt? Mine does. I hope this was clear enough for some of you to understand. If I am (once again) missing a simple "trick of the trade" let me know. If my undersatnding of wiring and relays is WAY off, set me straight. And, Thanks for the help! 

[Anonymous]

Using the 3 DPDT relays,hook the aux power to all 6 common common contact blades. Run one wire from each relay NO (normally open)  blade to each of the crossing flashers. Connect the remaining 3 NO blades to a common point and from that point run it to the sound module.

Dale Hz

[HopperSJ]

Dale, That's what I was trying to say in the second thought of my question. Thanks for confirming my idea AND making it a lot more concise than I could have!

[lionelsoni]

You should be able to do the job with the simpler (SPST, or "form A") relays.  Just wire each relay coil in parallel with one of the crossing signals and operate the signal-and-relay pair from the isolated control rail.  Then wire the contacts of all three relays in parallel and use that combination to operate the sound machine.