Reading the output of a transistor

Other Hardware General Electronics
8

clam-:
Thank you so much for the detailed information. That helps immensely.

  • Voltage across A and K, about 1.1V. Seems good.
  • Diode Multimeter Test voltage across E and C, 0.12 seems low, but it is firing
  • Voltage at Arduino pin is 4.86, seems okay
  • Current inline between Emitter - GND is 137uA, seems like it should be okay
  • Measuring the voltage of the Arduino pin between GND, is measuring 74mV when optocoupler is active, 4.98V when inactive. built-in LED is continuously active, but when printing the state of optoState, it appears to change between 0 and 1 appropriately.

So it looks like it's now operating correctly. I'm using an Arduino Uno at the moment to perform these tests. Maybe I did something wrong before, or maybe it was my previous Arduino.
Not sure why the built in LED is not changing state, but so long as the logic is detected that's all that matters for now.

Thanks so much for your help.

Cool! Glad to hear it's working!!
A couple (or three) of notes:

  • 0.12V on the Collector-Emitter is not low, it's great! You want this voltage to be as low as possible :wink:
  • What makes you think the built in LED is not changing state? Clearly it is, if you're reading a state change at the output of the Opto-coupler.