Create/design a controller for me

[Demon]

This is where I learned a lot about stepper motors and drivers:
http://groups.yahoo.com/neo/groups/mach1mach2cnc/info

I can think of 2 ways to be certain where the "head" attached to the main shaft is located.

1. There are optical readers that attach to the back end of stepper motors (that's why the shaft comes out both ends on some steppers). Signals from these encoders tell you exactly how much the motor has moved.

2. For short main shafts, there are optical strips that can be run along the main shaft. An optical sensor riding along this strip tells you exactly how far the head has moved (I saw this in a inkjet printer).

For both systems, take a reading at far left and far right, center is mid-way. There are probably dozens of ways to do what you want.

It's all a matter of knowing your needs. I wanted to do a DIY CNC with 0.001" accuracy for work on PCBs, accuracy is everything. It you're moving Coke cans, a center switch is good enough.



Note: measuring motor movement is less precise, there can be some play in the attachment under the head. Measuring actual head movement is the ideal method, but the mechanism may be unreliable in extremely dusty environments.


Also, if you want to return to exact center every time, a center switch will not give a true reading. If the head is moving left, it will stop a fraction of an inch to the left of the switch, and vice versa moving right.

Robert

(don't you hate typing a long post at the same time as someone else)