Author Topic: Characterize Spread of IR LED for Remote Control System  (Read 835 times)

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Offline Phoxtane

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Characterize Spread of IR LED for Remote Control System
« on: October 12, 2016, 02:18:44 am »
If I've got an infrared LED that I want to use in a remote-control application, how can I measure the spread of the output? I imagine with a visible-light LED you'd just put it up against a sheet of paper and rotate it while keeping an eye on the light cone formed on the paper, but that's a bit difficult to do with something you can't actually see...

My first instinct is to use a digital camera, though from the previous thread regarding IR LEDs I made, the ones typically used in remote controls (~940nm wavelength) don't show up nearly as well on cameras. Would taking the IR filter out of such a camera solve my issue?

In addition to this, I assume the best way to get the longest range out of my control system is to be running the LEDs at full power, or close to it - maybe even overdriving them since the control protocol only pulses the LED for a brief period of time.

Offline Augustus

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Re: Characterize Spread of IR LED for Remote Control System
« Reply #1 on: October 12, 2016, 09:28:03 am »
Just out of curiosity, why do you want to measure this? The usual way is to just look it up in the datasheet of your particular led, it's listed under "viewing angle" or "half angle" (theta) or something similar. There is usually also a nice graph picturing the permissible pulse current, depending on duty cycle. For a typical 5mm ir led in a remote control application this is usually somewhere in the range of max. ~1A or thereabouts. If you want something fancy a Osram "Oslon Black" SFH 4725S is able to handle up to 5A pulses. These are really nice, coupled with some narrow beam optics they would make a hell of a long range TV-B-Gone  :-DD

« Last Edit: October 12, 2016, 10:02:40 am by Augustus »
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