I have scavenged some photo interrupters from multiple printers but I am trying to figure out the polarity and the voltage. I've tried searching up photo interrupter polarity but couldn't find anything. On one of side of a sensor, it is labelled: A and K and on the other side it says E and C. It also says on the sensor H306-41. All the other sensors are unlabelled. Is there an easy way to find the polarity and voltage with a meter?

Edit: Images: Picture of labelled sensor:

Labelled sensor

Picture of unlabelled sensor:

Unlabelled sensor

  • \$\begingroup\$ A picture would help \$\endgroup\$ – Damien Jan 19 '19 at 7:19
  • \$\begingroup\$ The datasheet is easy to find. i.stack.imgur.com/FLITt.png \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 19 '19 at 7:28
  • \$\begingroup\$ Is there a website for datasheets like that? How do I find a datasheet for the sensor in the second image when there is no writing on the sensor? \$\endgroup\$ – TheTrialBot Jan 19 '19 at 7:38
  • \$\begingroup\$ Your 2nd photo shows only three output wires (one of them might be a common ground). Thus the common includes diode cathode, along with phototransistor emitter. Far less often, the common terminal is Vcc, or Vdd…in this case, one is diode anode, connected with phototransistor collector. \$\endgroup\$ – glen_geek Jan 19 '19 at 14:27
  • \$\begingroup\$ I put diode mode on my multimeter and found that yellow is the anode and blue is cathode. The positive wire from my multimeter went to yellow and the negative wire went to blue. So does that mean that blue is collector or emitter? \$\endgroup\$ – TheTrialBot Jan 20 '19 at 2:26

Usually the labels are as follow:

  • A - Anode, this is the LED anode (+)
  • K - Cathode, this is the LED cathode (-)
  • E - Emittor, phototransistor Emittor
  • C - Collector, phototransistor Collector.

The photo transistor base is basically the light from the LED.

enter image description here

| improve this answer | |
  • \$\begingroup\$ Thanks for that. How do I find the polarity on an unlabelled sensor? \$\endgroup\$ – TheTrialBot Jan 19 '19 at 7:40
  • 2
    \$\begingroup\$ measure on diode mode, that will find the led. power the led and re-measure the other side, lowest reading will have 'C' as 'A', ans 'E' as 'K' \$\endgroup\$ – Jasen Jan 19 '19 at 8:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.