IR illuminator - unspecified LED's

Discussion in 'The Projects Forum' started by toninph, Nov 3, 2011.

  1. toninph

    Thread Starter New Member

    Dec 10, 2010
    The LED's used in the attached schematic are of an undefined bulk type. The circuit works on 9V and 20mA on each string (see photo). But I do not know the spec of the LED's.
    Firstly, the reflector inside the LED is not the cathode but the anode, even though the reflector is on the flat side of the LED and the lead is short. So, it's the other way around from usual.
    Secondly, there are two junction wires between anode and cathode. Does anyone what that could mean? Do two junction wires indicate a higher allowable current, e.g. 100mA?. Is it possible to determine or calculate the maximum allowable current without blowing them up?


    I did a crude measurement of the IR output intensity by using a similar IR LED on top of the emitting IR LED and measuring it's voltage on a DVM. It was something like this:

    IR LED current Measured output
    10mA 300mV
    20mA 780mV
    40mA 850mV

    Assuming the general current/output intensity curve of a LED, it looks like the output intensity is saturating from 40mA. I don't think 100mA will increase the output intensity significantly. It would probably burn up the LED anyway. Can someone confirm that I'm on the right track?
    Last edited: Nov 3, 2011