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strange motor sensor inside scanner I took apart
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strange motor sensor inside scanner I took apart

by JoeELP on Tue Mar 31, 2009 1:54 am

hi, so I took apart a broken HP scanner, and I found an interesting sensor. I've attached a pic, but its a bit blurry


apparently, as the motor spins, it turns a thin plastic wheel with a design that passes in front of a sensor of some kind which it uses to keep track of rotations or something. My question is, what kind of sensor is this, and can I use it for something? Maybe motor positioning?

it has about 5 pins I think, 2 on one side and 3 on the other.


NOTE apparently I can't upload pictures yet. sorry!
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Re: strange motor sensor inside scanner I took apart

by westfw on Tue Mar 31, 2009 2:23 am

Probably an optical encoder, which is just a couple of photosensitive things and maybe a light source (infrared.) This allows the microcontroller inside the scanner to tell how far the screw has actually turned, as opposed to just how far it think it has told it to turn. It might allow higher scanner resolution if you can snap a scan line partway between stepper steps, too.

Conceptually, it's very similar to the sensors on old mechanical mice, only probably higher in resolution.
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Re: strange motor sensor inside scanner I took apart

by zener on Tue Mar 31, 2009 2:31 am

Yes. Could be a quadrature encoder.

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