Re: pot verse optical encoder
There are rotary pots made specifically for that application, they can
be expensive though.
Mechanical rotary encoders, RVDTs (Rotary Variable Displacement
Transformers), and synchros and resolvers are also used to measure
I picked up a handful of Grayhill mechanical encoders from
Allelectronics a couple years ago. I think they were 4 bit gray code
encoders. You haven't mentioned your accuracy, resolution or range
I wonder if you could hack a synchro together by taking a stepper, run
A/C or pulsing DC (NRZ) into the rotary element and picking the
strongest signal off the secondary?
Folks also put together DIY optical encoders using reflective painted
(black/white) pinwheel designs and optically coupled elements.
--- In firstname.lastname@example.org, "jownzie" <smjones1969@s...>
> I am working on a device that needs to monitor the position of
> something. It is an angular displacement and I have geared the pot
> go almost one full turn giving me maximum resolution. I like usingflaws.
> this method becuase of its simplicity but there are a couple of
> The first is I suspect the POT could potential give bad readings asit
> is sliding around, even with a filter capacitor in place. I have notfeedback
> witnessed this but have not conducted any tests. Even if the
> ocasionally bounced, it probably wouldn't be too bad since theanother.
> sampling and calculations would be happening one right after
> The other concern is that pots have a rated life. I am thinking ofcomplex
> manufacturing this project and can't deal with something that would
> expire after a year or whatever. So the best next idea I think is to
> use an optical encoder in place of the pot. I don't like using the
> encoder for a couple of reasons. The first is it is a bit more
> than simply reading an A to D conversion. The second is that isalways
> relative to a reference, while a pot gives you true position. Andthe
> encoder, from what I have saw, are easily 30 dollars even for asmall
> basic one. So I guess my question is this? Would I be able to getaway
> with a pot in this application. How long do pots last? Can I ensuredo
> the pot will give true readings as it is sliding around? I know you
> not know all the specifics, but basically the pot would be simplymeaning
> sweeping full range back and forth driven by a small DC motor,
> the speeds would not be incredibly fast.