Re: U.S. Digital encoders

Hi Alan,

OK, you're just talking about "parts". Thought I missed something.

This encoder is quite simple, in addition to the two transistors, a few
resistors, and the LED with a GE number on it. I'll see what an
incandescent light does to the output of the photocells.

Alan KM6VV


Alan Rothenbush wrote:

>
> > 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