I have a filter wheel made by Andy Saulietis. As provided the "Andy Wheel" must be manually advanced. I built a stepper motor controller with Maxim/DL driver
to automate it. Here are some photo's.
The first photo shows the completed wheel with RJ45 cable to the interface box.
The second shows a detail of the stepper mounting and faucet washer 'drive'. The motor swings around a screw mounted in the fw body on one end and a radio dial spring on the other end provides tension.
The third photo shows half of the emitter/detector pair used to sense the edges of the opening in the wheel. You can also see the 'index hole' used to provide an absolute reference position.
The photo on the left shows the controller box. The right shows it's interior. This box contains an 8052 microprocessor with a serial interface to my scope control PC. This controller provides all of the intelligence for the wheel. It is cabled directly to the motors and sensors on the wheel. The stepper driver is made from discrete power transistors and it's claim to fame is current limited 24V drive with 2 levels of current selectable. Driving a 5V motor with 24V provides a very fast rise time which overcomes the inductance of the motor and provides a high step rate. The current limiting prevents this from destroying the motor. Most of the ideas for this driver were obtained from a Thomson Airpax document describing stepper motors. The two stage drive allows a higher current for stepping and a lower 'hold' current. In practice the motor holds perfectly well with no current applied. The index sensor originally just used the single index hole to close the feedback loop. In the event the wheel slipped this could cause filter misalignmemt. This was fixed in software by using both 'edges' of all 4 filter holes plus the index hole to provide 10 points of reference on the wheel. Only a small distance remains at any point to be traversed 'open loop'. I purchased the 'plug in kit' for Maxim/DL from Cyanogen to write the Maxim interface.
Here is the dialog box for the wheel in Maxim/DL
