Work in progress of another engine sound unit that replays true recorded sound files - but this time they are stored in an SD Memory Card.This allows the user to supply their own set of (start/run/stop) sound files to suit the model in question. The length and the quality of the sound samples is no longer restricted by the microcontroller memory space (FE100/101 offer just a few seconds of 8bit, 8K samples/sec) - the SD card storage far exceeds that required for all practical purposes and up to 12bit 22K samples/sec files can now be played.
The three boards you see above (Adafruit WavShield, my RC interface & the Arduino form into the stack seen here on the left. A future version would combine my RC interface with a subset of the Arduino hardware (eg the USB interface is not required) onto a single custom PCB to mate with the WavShield. A neutral adjust push-button and run status LED would also be included. A second RC channel is under consideration for adding a further user triggerable sound (eg a horn) but this would momentarily *replace* the engine sound rather than overlay it.