Multi-turn rotary encoder

[kazam]

Hi, I have an application where I need to be able to measure 100 turns of rotation of a small plastic shaft, diameter 6mm.

Ideally I would like a 10k, 100 turn potentiometer. It needs to be absolute positioning. Accuracy is not critical.

Searched the usual places but could only find 10 turn pots.

Ideas, anyone?

/K

[ebastler]

100 turn pots are available, e.g. from Vishay: https://www.vishay.com/docs/32531/rp12multi-turn.pdf. Expensive, I‘m afraid... Or you could use a 10x reduction gear and a 10-turn pot.

Do you need to just count full revolutions, or resolve angles within each full turn? Mechanical revolution counters would be the traditional solution if full revs are all you need:
http://www.fargocontrols.com/counter/mechanical.html

Personally, I would prefer to move away from the requirement for absolute encoding if possible, and have a microcontroller monitor a cheap quadrature encoder all the time. This will require zeroing or otherwise initializing the position upon power-up, of course, which may or may not be feasible.

[james_s]

You could use a small 10:1 gearbox to drive a 10 turn pot. There is probably something off the shelf that will do that, I do like encoders better than pots though.

[Nusa]

A rotary encoder (title) and potentiometer (text) are different approaches. From what you've said, i'd lean toward an encoder as well. If the shaft turns rapidly or constantly/frequently, an optical encoder might be best.

[abyrvalg]

Linear pot + screw is another option