Testing Infrared LEDs

Discussion in 'General Electronics Chat' started by uriahsky, Apr 27, 2009.

  1. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    I have a bunch of Infrared LED emitters and detectors that are either loose or in scrap pcb's. How would I test them to determine their properties so that I can use them for repairs. Is there some low-cost test instrument that can do this? Or anyway to work it out?
    Thanks, I am new here..
  2. Darren Holdstock

    Active Member

    Feb 10, 2009
    You may be able to test the IR emitters by looking through the viewfinder of a mobile phone camera, or digital camera - for some reason the sensors show the IR as visible blue. Testing the IR photodiodes could get quite complex, but you could start by putting one across a 50 Ω terminated 'scope input and pointing a known good IR source at it, modulated to a square wave. If the IR source is fast then the speed of the PDs can be roughly gauged by measuring the rise and fall times.

    Normally photodiodes are used with transimpedance amps, but such TI amps are tuned to the PD characteristics and so generally won't work well with random PD selections.