I've used switches from Omron to good effect - you probably need one with a
slit aperture in front of the detector side which makes them much more
precise at the expense of a little sensitivity. The ones with integrated
opto-IC rather than a simple phototransistor on the detector side are easier
to interface and likely to be pretty consistent unless you have huge
variation in ambient infrared levels.

The other thing which affects repeatability is the mechanical accuracy of
the system. If you can ensure that the that the blocking edge is towards the
detector side of the slot - or at least is in a consistent position across
the slot, then it will be much more repeatable.

Philip

John Leonard wrote:
> Folks,
>
> I'm trying to find a slotted optical switch that has a very small and
> accurate sweet spot. I've been testing the common or garden varieties and
> getting results that are too hit and miss for the project I'm undertaking. I
> really need an accuracy of 1mm between on and off states. I've played around
> with masking an existing switch, but if there's something that has a greater
> accuracy from the start, I'd be very interested to know. This is for a
> project where I cannot have anything connected to the device that is moving
> and providing the trigger.
>
> Thanks in advance for any information.
>
> John
>
>
>
>
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