Why so many photosensors?

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  • JR2ALTA
    Service Manager

    Site Contributor
    1,000+ Posts
    • Feb 2010
    • 2017

    Why so many photosensors?

    As far as I know, the size and "clip in" feet of photosensors are damn near universal. And a photo sensor is either resting ON or resting OFF. To me that's a very binary concept.

    So does a given machine have more than two part number for their photosensors?

    Sure, I have tried out a few wrong p/n in a pinch and they also seem to work out but I would like to better understand the engineering of it if anyone knows.
  • blackcat4866
    Master Of The Obvious

    Site Contributor
    10,000+ Posts
    • Jul 2007
    • 22702

    #2
    Re: Why so many photosensors?

    I can contribute a little.

    You don't specify a manufacturer, but each manufacturer is consistent in its own way.
    Toshiba, for example, has only two or three basic paper sensor types in any particular machine build. They have a different sensor for high heat applications like exit sensors or web detection sensors (C0-10814000), but the rest are usually the same.

    The most common sensors out there, and the most troublesome are the SHARP73 that had a few bad years, in which we replaced sensors by the bucketload. They seemed to cause a logic lockup on the controller board. If you were to just unplug the sensor and plug it in, the jam condition would clear and the machine would resume function ... until tomorrow. These same sensors were used on everything, so you might experience it as a door that shows open, a developer shift error or a motor clock pulse error.

    Kyocera seems to use the same two types of sensors on everything, one reflective, one photointerrupter.

    Lexmark likes to attach wires to their sensors, so every single application has wires of a different length, and many different varieties of photointerrupters.

    Other sensors you might see are usually labelled like this (where the xxx are numbers):
    SGxxx
    NLxxx
    BLxxx
    When I see one of these, as long as the first two letters are the same, the sensor usually works. I'll match the numbers if possible, but it doesn't seem to be necessary.

    I have a large miscellany of sensors, just for occasions like this. The most memorable was a Kyocera finisher in which I had ordered an elevator tray sensor. Both the old sensor and the new sensor would not change state, then I started digging through the miscellany. Of the 100 or so sensors on-hand, (3) had the correct connector and changed state properly. Of the three, (2) had the correct mounting legs. It's pretty frustrating trying 100 photointerrupters, and testing live with a meter, to see if it changes state. I'll remember that one for a long time. =^..^=
    If you'd like a serious answer to your request:
    1) demonstrate that you've read the manual
    2) demonstrate that you made some attempt to fix it.
    3) if you're going to ask about jams include the jam code.
    4) if you're going to ask about an error code include the error code.
    5) You are the person onsite. Only you can make observations.

    blackcat: Master Of The Obvious =^..^=

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    • JR2ALTA
      Service Manager

      Site Contributor
      1,000+ Posts
      • Feb 2010
      • 2017

      #3
      Re: Why so many photosensors?

      Thanks. I was thinking of Sharp actually. They seem to have different ones for ADF, PPDs, APPDs . The fuser makes sense to have a different material but it sure looks like same.

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