I’ve been intending to try driving Switec X25.168 motors using the MCP23008 I²C I/O port expander chip from an Arduino, but it occurs to me that it might be more interesting to try this on a Rasberry Pi. If it works, it will demonstrate a simple and very inexpensive method for driving analog gauges from the Raspberry Pi without the need for high-current drivers.
Phil Bambridge has blogged about his Beverage-o-Meter which demonstrates wireless remote control of an analog gauge using Arduinos eqipped with Nordic 2.4GHz radio boards. Fun, whimsical, and beautifully housed too. His project uses a Switec stepper for the gauge, and uses the SwitecX25 library. Check out his blog and source code here.
I am aware of three companies manufacturing compatible motors. All appear to produce a good-quality product.
I recently removed the internal stops on a VID-29 stepper. I’ve used this free-turning motor and an optical sensor to exerimentally test some operational limits of the motor. The test rig uses a photo-interruptor to determine the needle position:
A quick note about wiring harnesses for these motors. I’ve found it really handy to make harnesses from 4-wire CD audio cables. My harnesses use push-on connectors at the motor end so I never accidentally cook the motor by soldering to the motor pins.
