Electronics

nagaloo · Posted: Tue Oct 31, 2006 2:36 pm Post subject: Whats up with this LED?

I have 2 pairs of LEDs I want to use on a project Same manufacture One set is red one is blue. When I power the 4 together the blue ones dont light up. They operate ok once I unplug the red ones from my project board. I tried a different manufacture LED and get the same results.
I am not very electronics savy its a simple lighting and switch project Just a power source and a resistor to reduce the voltage to the LEDs
Stew

neon · Joined: 25 Feb 2006 Posts: 594

It very simple not all devices are created equal. Some takes up to 100ma to light up with 4v some take 1.7 v and 10ma. LED do not light up not until it has reached its very minumumn, If you put them in parallel some will never light up even thought some current flow trough.

nagaloo · Posted: Wed Nov 01, 2006 2:26 am Post subject:

So I should power each with its own resistor? Another thing- I have a 24vdc supply would it be better to use a lower voltage and need less resistance or does it matter?

neon · Joined: 25 Feb 2006 Posts: 594

in series you need one only resistor provided that min. current is there and guess what max current is not exceeded. if all are of the same type then find the a current that will lit them up and use 24 v [- ] all LEDS v drop and use that voltage to calculate the R. YOU CAN USE 120 AC IF YOU WANT PROVIDED that you do not exceed the parameters. they are diodes of a kind anyhow. And finaly it is not the current that makes them fail but heat or power if you will. actualy practicaly all of these guy will laser with hi energy for naoseconds of time with lot of currenthough them..

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