Any LED Experts Here? Please Read and Advise.

[MikeM3]

Hi all, it is some time since I visited this site,
but here I am looking for some guidance.

When I last worked seriously on electronics
they were all glass valves, so I know nothing.

I tried to convert a LED work light to infra-red
by removing the bright white lights and fitting
IR lights at 850 nm, there are 24 lamps, powered
by 3 X AAA batteries, when I switched on nothing
happened except the resistor got very hot.

I may have been sloppy in my soldering and left a
short circuit somewhere on the board, though I
like to think that I didn't, if not that can you tell
me why the circuit didn't work, I assume that the
different colours of LED have different electrical
values, but I have no idea what they may be.

There was a small calculation where I had to know
the voltage supply + the voltage of the lamps time
a large number that I can't remember, nor can I find
it again on the internet.

Any advice and guidance will be accepted with a lot
of gratitude.

Thank you in advance.

Mike.

 

[Marvo]

Yes, the forward voltage of LED's changes depending on their light frequency. From memory red is usually lower (maybe 1.8-2 volts) and blue would be higher (maybe up to 3.5 volts). There's also variations on recommended forward voltages according to different manufacturers so it's best to refer to the specific data sheets for the component being used.

 

[Marvo]

Obviously this means you can't just remove a blue LED and replace it with a red because it's doubtful the red will survive being overdriven by the voltage that was originally intended for the blue.

Maybe attach some pictures of the array you were working on.