Skip to main content
shopping_basket Basket 0

What Sensor Do I Need?

Hi there, please could you help me decide what sensor I need for this application.

I need to count how many times a shaft has rotated and in which direction.

The user turns a knob attached to the shaft, I want to display what level they are at, the more they turn the knob the greater resistance is placed on the a wheel.

Any help would be greatly appreciated.

Thanks in advance,

Stuart Roberts.

0 Votes


May 18, 2020 11:16

At the simplest level you could use a slotted opto and place a vane on the shaft or use an inductive sensor sensing the teeth on a toothed cog. However if they reach the maximum level they can achieve just at the point where the counter changes (i.e. the vane breaks the opto beam) you will suddenly get multiple counts from the repeated beam breaks.
Moving on you can add additional sensors to make a simple encoded output which with appropriate electronics and/or software will not suffer from false counts. Or purchase a shaft encoder.
Depending on the number of rotations of the shaft and if these could be physically limited to less than 10, you could also consider a multiturn potentiometer.
But you will damage the pot if you force it beyond the 10 turn limit. This solution, however, would just require a simple A/D to read or even just a voltage display.
Hope that helps you to decide.

0 Votes

May 18, 2020 11:16

@Stuart, just re-read and saw you require direction also so the simple opto solution will not provide that and you need an encoder or multi-opto vane solution.

DesignSpark Electrical Logolinkedin