Driving a IR led

[robertpatterson]

I am trying to drive an IR led It seems to get any brightness at all I have to run it straight off the output pin (no resistor) Is there a chance my pic chip will fry in hell for that. running at 38khz it doesnt register any current on my amp meter.

[JohnCrow]

Hi Robert

An IR LED is invisible to the eye. If you want to see if its working look at it with the camera on your phone, (or webcam etc)
You will be able to see it glowing a that way.
Running without a resistor will certainly burn out the LED sooner or later.

[robertpatterson]

It doesn't appear to draw as much at 38 khz

My amp meter doesnt register any draw

[JohnCrow]

Hi Robert

I think 38 kHz is quite a high frequency to measure current at under this application.

My Fluke 87 is only specified 45 Hz to 2kHz ac current. So I don't think you will get much indication.

[robertpatterson]

Yes I was monitoring the flow from my power supply to the PIC it wasn't anything alarming.

[robertpatterson]

My Marconi 2955b says 5 volts on the out pin and 1.25 volts on the led going through a 100 ohm resistor

Time to do some math from here.