Author Topic: Infrared Recievers  (Read 1248 times)

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Offline skillz21Topic starter

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Infrared Recievers
« on: October 16, 2016, 01:40:25 am »
Hi guys,
A while back, i got a pack of IR transmitter LEDs and receiver LEDs (is that even what their called?). I know i can just use the... ones with a chip built in, but i want to know what these things are used for. :-//
Thanks!
PS.Sorry for the informality in my posts :)
 

Offline Ammar

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Re: Infrared Recievers
« Reply #1 on: October 16, 2016, 03:30:15 am »
How many pins do the receiver ones have?

If it has two pins it is likely a phototransistor or photodiode.

The ones with three pins contain a photodiode as well as a bunch of other magic (filters, amplifiers, demodulators) to ensure that the device receives signals that are modulated at a certain frequency, typically 10s of kHz. They will have a supply pin, a ground pin and a signal pin.
 

Offline skillz21Topic starter

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Re: Infrared Recievers
« Reply #2 on: October 16, 2016, 03:56:46 am »
two pins, click HERE for image.
 

Offline Ammar

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Re: Infrared Recievers
« Reply #3 on: October 16, 2016, 04:01:07 am »
I am guessing the dark one is the infrared LED although it could be the other way around.

The clear one is likely a phototransistor. The longer lead is probably the emitter and the shorter one the collector. You can test it out by putting a 10k pull up resistor on the collector to a supply voltage, say 5 to 10V. Shine the infrared LED on the phototransistor and measure the collector voltage with a multimeter. Watch it drop to around 0.7V when the light is shining on it.

You can also check to see if an infrared LED is actually glowing with a CMOS camera. Although filters have gotten better these days, so maybe not. My camera phone still shows glowing infrared LEDs as purple light.
 


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