Re: Re: U.S. Digital encoders

> I'm currently trying to repair an old Vernitech (M15-127) panel shaft
> encoder, so I'm curious U.S. Digital's "homemade" encoder? I didn't
> find it, can you be more specific?
>
> My current thinking is that the LED is out. I don't know if it is IR or
> not. I've replaced two 2N3906 transistors, still no luck. It looks like
> about 256 cpi, and by rotating the encoder wheel, I can see about 4
> "slots" alternately aligning over each of the photocells in the flat
> pancake sensor.

Here's the link to it again

http://www.usdigital.com/products/em1/

Now, by "homemade", I mean a USDigital designed and built unit. Previously
they sold HP/Agilent encoders.


As far as the repair of your unit, I would suggest that it is much more
likely that the LEDs are defective than any other piece. But without
seeing the unit you're talking about, I may be totally out to lunch.

The manufacturer may have taken extra pains to produce nice clean
quadrature. Inside of one HP encoder I was looking at, they had a constant
current source to drive the LEDs and schmitt triggers on the output - a
bit more complicated than the "LED and 2 phototransistors" I described.

To test the photosensors, you can always use an incandescent light bulb.
They have enough IR and visible light output to turn on most any sensor.

Alan




--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
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