Testing LED Specs???

[Zero Cool]

With My recent playing with some LED's i have discovered i have a large box of unknown LED's on hand. Making them light up is easy enough, but is there a way to test them to figure out what the voltage and current should be without blowing them up??


Zc

 

[I_Forgot]

The vast majority of LEDs are spec'd to run at 20 mA. Make a 20 mA current source and measure the voltage drop across the LED if you must, or just assume about 2V for red and maybe 3.5V for blue and green.

I_F

 

[AndrewT]

Hi,
a 9V pp3 battery + 2k2 resistor + LED + Multimeter + some wire = full testing kit.

If you want to test at various currents then substitute alternative resistors.

 

[Zero Cool]

I cant light the diodes easy enough. but what i want to know is how to measure what there rated voltage and currents are supposed to be.

Looking up LED specs i see that there are a lot of choices depending on brand and model etc.

I have 3 or 4 different types of T-3/4 Red leds. some are 2.1V some 5V some 12V and some are weird 1.2V an the currents seem to be all over the place as well. some 20ma or so some 30 one is 50 and some are 5ma.


I just thought there might be an easy way to measure and figure it out.

 

[AndrewT]

Hi,
any LEDs that need 5V or more, incorporate a driver circuit. They are no longer LEDs.
I have never heard of a 1.2V LED.
Most LEDs are in the range 1.5V to 4V and need external current limiting.
You can easily measure the Vf using that test equipment.
Run @ 2mA and see how bright they are. Try 5mA and if it burns out then that was too much.

 

[suvatn]

http://www.ledtronics.com/datasheets/Pages/led_color_chart/38.htm

The chart from this link may help you some.

Led have several types, colors and development are very fast.
Basis, normal foward voltage will 1.x to 5.x
If you put constant current 20 mA, measure Vf, see color, see
how bright.
You may find it.