I think I know why the transmitter doesn't have decent range. When the MP3 module is actually playing a song, it's stomping on the RF signal to the receiver! It works great to start the first sound, but if I want to change the sound from the transmitter, I have to be pretty close to the receiver to get it to work.
So to be clear, you got 30' "reliably" for which functions / under what conditions?
I understand you back-burnered the direct RF remote for now, but in the context of an O-gauge layout what would you (or anyone else following along) consider to be decent range?
I like the door-opening idea as it fits with so many other rolling-stock accessories where you trigger it, the door opens, something happens, the door closes. Is anyone else following along? If there is really interest in mating some kind of mechanical action to the sounds, I've been messing with the idea of using a stereo MP3 module to put sound on one track and mechanical commands on the other track. For example a series of audio bursts can be sent not to a speaker but to a 25 cent bridge-rectifier to create the DC pulses to drive a PWM hobby servos that GRJ mentions. Maybe someone has done this already but that would be one way to synchronize sound and motion without requiring a processor chip and writing software.
