I'm trying to make an IR receiver-emitter pair to provide the signals for a larger circuit. I've used the standard circuit for the receiver emitter pair. I've enclosed a picture of the circuit.my circuit drawing Is there any way for me to test whether the LED is working fine at the current I am sending through it? The cause of my concern is that I think I may be spoiling the LED while soldering it. Also, what would be a typical operating forward current for the LED? Any advice would be extremely welcome. I'm a second year undergrad of EE. ( I'm stating this because there has been some concern lately about the competence of users.)

  • \$\begingroup\$ Typical forward current and voltage are in the datasheet for the LED. You do have a datasheet, right? I estimate you are getting around 7mA through your LED (that's using guesstimated Vf.). What makes you think your LED isn't working? Try looking at it through a digital camera - lighted IR LEDs appear as a sort of purplish colored light when viewed that way. \$\endgroup\$
    – JRE
    Commented Jun 9, 2017 at 7:42
  • \$\begingroup\$ is the LED lighting up when you use it? (you can use the camera you used to take the above picture to see the IR waves as pink) \$\endgroup\$
    – dandavis
    Commented Jun 9, 2017 at 7:42
  • \$\begingroup\$ Measure the voltage drop over it, hence work out the current through it with your resistor values. You can check the LED is working by either monitoring voltage changes on the IR receiver, or use an old / android smartphone camera to detect the IR LED and whether it is emitting or not (provided you can see if of course). \$\endgroup\$
    – MrPhooky
    Commented Jun 9, 2017 at 7:43
  • \$\begingroup\$ It's working! I just increased the current as advised, and then verified by camera and then by an LED in parallel with the receiver. \$\endgroup\$ Commented Jun 10, 2017 at 4:57

1 Answer 1


You can check the LED by checking the photodiode operation. You should have output when the LED is on.

The LED current will be in the data sheet.


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