And what would be nice would be the ability to preset a number of turns and let it count *down*, and have it output a signal to stop the lathe when it has the right number of turns.
Enjoy, DoN.
A classic logic design problem. The problem is how then do you reset the latch? If you use the switch going off, it will just follow the switch on & off.
Way back, when I was doing logic design, we used one-shots (monostables), which were triggered by the switch & whose output was the clean signal. It could not be re-started until it had timed out & it's duration was longer than the bounce time.
Bob
Dollar Tree sells a small LED light with a reed switch & magnet to control it. You get a free coin cell, too. :)
Well, the counter part is easy enough: Red Lion Controls makes little counter modules, Cub and Sub-Cub, that will give you a half dozen digits and run on penlight batteries. $20 to $80 at DigiKey.com.
If you can clamp a magnet to the chuck, and position a reed sensor (like bicycle speedometers and open-window security sensors use), that completes the task. If you want to get fancy (multiple magnets and sensors to get clockwise/counterclockwise indications and an up/down counter), that's possible, too.
If you can access the shaft that drives the chuck, you can put the sensors inside the gearbox, of course. If you could get a cam onto the shaft, it could work the lever on a mechanical tally-counter, and that doesn't even need the penlight batteries. This, I've seen integrated into lightweight lathes for coil-winding.
Red Lion CUB3 counters work pretty well.
The thing to be aware of is that the CUB3 requires a pulse width no shorter than 5 or 10 milliseconds (check the data sheet), and many magnet and reed switch arrangements don't achieve sufficiently wide pulses above some speed, so the count becomes unreliable above that speed.
Joe Gwinn
Just the other day I received the Red Lion Cub 3 counter from Digi-Key. Slicker 'n Snot, too. Stuck a magnet on the backside of the chuck, and placed a small round reed switch (the kind the fits into a drilled hold in the door jamb and the round magnet gets mounted in the edge of a door. Sucker works GREAT - Thanks to all for the suggestions - AMAZING group of guys. Ken Sterling
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