how to distinguish between IRLED or IRphotodiode/transistor

[nikhilele]

I have got IR LED and IR photo transistor but now they are mixed.
I want to know which are IR leds and which are IR phototransistor

interestind thing is IR phototransistor have same looks as that of IR led.

can we used forward and reverse voltage measurements to distinguish between them.

 

[dfullmer]

Re: how to distinguish between IRLED or IRphotodiode/transis

You should certainly be able to drop volatge across them each (at very low current) to see which one conducts down to a 1.2 Volt drop. This would be the diode. Once you have what you think is the diodes drive them a little harder to turn on. You can check with a video camera to see the IR output from the diode. Most older video cameras will see down to about 1 micron wavelength.

 

[nikhilele]

can we make it out just by measuring voltage drops

 

[IanP]

Re: how to distinguish between IRLED or IRphotodiode/transis

Take 1kΩ resistor, 4.5-5V power supply (battery) and connect in series with a cmponent (IR diode or transistor) .. see picture below (use 1kΩ) ..
If it is IR diode (IR LED forward voltage drop of about 1.6-2V) you should measure in one direction 1.6-2V and full 4.5-5V (power source) voltage in the opposite direction ..
If it is IR phototransistor you will measure roughly 4.5-5V (supply voltage) in both directions, unless this component is exposed to the IR radiation, and fully exposed to the IR may show voltage of <1V between collector and emitter ..

Rgards,
IanP

 

[dika]

Re: how to distinguish between IRLED or IRphotodiode/transis

a note on testing the IR LED...
just take a digital camera and turn on the IR LED, if its bright... then its surely a LED
for an IR LED the colour should be kinda white/bright blue

 

[nikhilele]

i donot have digital camera
but i have multimeter and variable powersupply.

 

[nikhilele]

Now i have a digital camera in my mobile phone
i have moto l6 and i see ir through that
but both ir photo diode and ir led are glowing when connected to 1k resistor