Reply to "Wireless remote control of features in rolling stock from locomotive"

This being a discussion forum...

 

Don't try this at home  but it occurred to me that you might be able to simply remove the 12V relay (unsolder the 5 terminals in yellow box) and drive the music module with the relay coil voltage!  In other words, when the module is triggered, it applies 9V (or whatever DC battery voltage you have) to the two coil terminals of the relay.  The relay then closes and then applies the same 9V DC via the relay contacts to the music module.  Skip the middle man (the relay).  Obviously the 10 Amp switching capability of the relay is overkill for this application!

 

There are i's to dot and t's to cross.  First is to determine the +/- polarity correct as to which coil terminal gets which polarity when triggered...that should be easy to determine by inspection or measurement.  Another would be to confirm the transistor that drives the relay coil has enough power to drive the music module.  That's a little more involved and would require, say, measuring some DC currents with a meter.

 

Anyway, just thinking out loud here.    Perhaps this approach (removing the relay) could be used in other remote-control-of-rolling-stock applications of, say, a few LED lights where you don't need the high current capability of a relay.