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IR Photo Interrupter help

Discussion in 'General Electronics Discussion' started by rm187, Aug 14, 2019.

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  1. rm187


    Aug 9, 2019
    I have found a cheap "StableTemp" Cole Parmer hotplate stirrer. Ebay. I thought it was 100% but maybe I read the description wrong, I haven't even rechecked because regardless its now my problem to fix.

    It has a digital control system, lcd temp and stirrer. ( it has a RPM sensor/set and trys to keep the RPM regardless of viscosity ).

    The stirrer motor works and I have used it. After about 30 seconds it turns off with E05 on the LCD. The RPM sensor does not appear to be working. You set the RPM, motor turns but LCD always reads 0.

    There is a small...ticker wheel [kinda its just cut outs evenly spaced] under the stirrer with some IR Photo Interrupter that reads RPM..

    So simple, but it doesn't read my RPMs.
    The desolderer IR LED is the original. I replaced it with a cheap raspberry pi one I had.. I believe its the 3 leg IR.. But this is a hard part to put my finger on... It can have a amp? and such in there...

    I originally tested with my phone camera to see purple IR, got nothing.

    Anyway, I found you here because of this thread
    I have the exact same markings. 7STS-04 94v-0 - So google sent me there instantly... The part in that thread is slightly different.

    I need help identifying the black IR transmitter? As I read more about these its quite hard to tell what I have.

    Also I would like to state that shorting the sensor pin on the main board with no sensor connected-- produces RPM readings on the LCD. So I am really sure its this 50c part is killing m 20190814_005620.jpg 20190814_005602.jpg e.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Unlikely. These parts consist of an LED and a phototransistor only.
    Check the current through the LED. If there is no current, the LED will be off and the sensor will not work.
    Almost any similar component will probably work in this situation.
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