Question and guidance - count rotating shaft forward/back

Hi everyone -

I have what I hope is a fairly basic question -

I want to measure the rotational position of a shaft.
Ordinarily, that’s simple enough ---- if the shaft does not go around more than one full circle.
I’d like to do this with an Arduino and report the shaft position with an LED display (not LCD due to dark conditions, but I could adapt)
But – my challenge is that the shaft will rotate clockwise something like four to five full rotations and stop,
and then rotate backwards the same number of turns back to “home” and stop.

So a typical measurement might be from 0-20 for the first full rotation, 21-40 for the second rotation, up to 100 at the end of the fifth full circle.

What I’m doing, just for background, is measuring the position of a roller inductor which has RF energy applied
(hence I cannot simply measure the inductance or something - the high RF voltage present on the coils would destroy a sensor and Arduino.
And yes, this is an amateur radio antenna tuner inductor, for you hams out there)

I’d think of a rotary encoder coupled to the shaft- – but do those count multiple rotations, or only one full turn like a potentiometer?
The multiple rotations and needing to track which “full rotation” you’re on is what puzzles me.

Basically, I guess I’m looking for the electronic equivalent of one of these, and then
integrate it into an Arduino to display the output count, backwards and forwards.

I don’t want something that only counts upwards (quantity counter) and then needs to be reset to zero.

thanks for advice to a newbie!

Hi,

It seems what you would need is to use encoders. They will give you information on the position change of the wheel so you will be able to count turns forward and backward.

There are hall effect encored, standard quadrature encoders and optical encoders.

Here is where you will find all our encoders.

Lets us know if you have any questions.

Best regards,

Thanks Simon!

I didn’t realize that an encoder could count multiple turns, although I should have given that a VFO knob that will go in multiple circles…

How sensitive to RF are the typical encoders?

The next part of the plan is to try to figure out whether or not I can mount the Arduino inside the tuner housing, or whether the RF will interfere with the encoder at least,
if not the entire Arduino…

Thanks, Tim

Hi,

Maybe using optical encoder could be a good option. You should shield the wiring for better noise immunity but at lease the sensor itself won’t be affected.

Best regards,