Tachometers and speedometers on contemporary vehicles are often driven by stepper motors. On startup they go through a self calibration to find a known rotary position. I'm trying to find out how that is typically done. There seems to be a few possibilities:
- Drive the needle to a stop at max scale reading and somehow determine when that stop is hit (read motor current or what?)
- Use an electrical contact at some point on the scale
- Detect the position optically/use an encoder.
Anyone know how this is done?