For those that have been following along, after a period of "aging", the Wheel Speed Sensor board has been completed. Recall that this board takes an input from a reed switch and magnet on a wheel or you can use a hall effect sensor as well. The board outputs trigger pulses based on the speed the car is moving, that being based on the speed of wheel rotation. As delivered, it outputs four triggers for a sound board based on speed.
- Stopped
- 0-10 MPH
- 10-20 MPH
- Over 20 MPH
Obviously, these values could change fairly easily, they're all in the on-board uP code.
One reason for the delay is I had an issue that I was scratching my head on, it turned out I was looking in a totally wrong place! The board is supposed to power up in the stopped mode and output a pulse to initiate the stopped sound track. That allows you to have it trigger a sound when you power up the car, even though it's not moving. That wasn't happening, and I couldn't see why in the code! Finally, I got it on the bench and determined that is was outputting the correct pulse, the MP3 module wasn't seeing it! Apparently, the MP3 module needs some power up initialization and doesn't look at inputs until that's done. Mystery solved, and now the word works as intended with the Sound Board.
Here's a typical freight car implementation with the MP3 audio board and the Wheel Speed Sensor board. This gives you four sounds triggered as described above. Also, I left sound #1 open, that allows you to use the RF remote for an "on demand" sound from the car and still have the track speed triggered sounds.
You'll also note that this board is powered from that optional 5V output on the MP3 board.
