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Need assist with a 2 Axis encoder that controls motor speed

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Supertechster

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Some of you may enjoy this problem, I simply cannot figure it out.

For a big birthday present, I bought my wife a Long-Arm quilting machine complete with quilting frame for it. The machine sits on top of 2 roller-bearing equipped boards which allow her to move it forward and back (push and pull it), and move it from left to right... and make loops, zigzag and circles by hand easily.

I'm adding 3-4 axis CNC control to it, and a computer will then take over the X and Y motions and the Z or needle motor speed, which I plan to 'automate' with a small but beefy stepping motor belted directly to the rear handwheel already on the machine. Z will vary depending on what pattern or design she is quilting.

Now, my problem is, when the machine is in 'Manual' mode, and the CNC motors physically disconnected from the carriage (so there is no load when she manually moves it) she wants to have the needle speed automatically controlled based upon the speed of uni-directional movement of the machine on its platform. She calls this 'Stitch Regulation'. It speeds up or slows down the motor according to the speed and direction of the carriage, and provides for perfect, uniform length and density stitching. It also stops the needle motor too, when it stops moving so the machine does not stitch.

I butchered a few of the older encoder wheel type mice and am attempting to rig these to tell the motor when to run and when not to. Both will be attached to the carriage bottom part, one so that its wheel is held against the long rail of the X axis, to detect the carriages side-to-side motion. and the other with a bit of ultra fine piano wire looped about the shaft, to detect when the carriage top part is moving forward and backward (Y axis).

What method, chips or circuit (PIC/CMOS/TTL) can I sample the encoder outputs with and then use that to control the motor speed?

The longarm machines motor is a 90v DC model whose operational or 'stitching' speed is controlled by a blackbox atop the machine. I figure it's either an SCR or TRIAC device. It has a 2" dia exposed knob. She adjusts this manually and it is usually set between 3 and 5 (of possible 0 thru 10 in 270deg of motion)

Now, I can rig a small stepper to its control shaft, but how would I control it, or the handwheel stepper, by the encoders output?... or another idea, how would I use the encoders output to replace the SCR/TRIAC function and drive the 90v motor thru a pair of MOSFETs directly?

To keep things simple, I am leaning toward the stepper-control approach.. but you folks are the experts.

So I guess what I need your collective help with is a circuit to decipher the outputs of the 2 rotary encoders, and then using that to either drive the medium power stepper motor on the handwheel, drive a a tinier stepper motor attached to the SCR/TRIAC speed controller, or to directly influence the speed and acceleration of that 90vdc motor. It, like the handwheel stepper, only ever turns in one direction

Do any of you folks have an idea, design or schematic I can start with? I now know how to detect, amplify and cleanup the signals from the opto encoders... but what next?

Any help is much appreciated.
 

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