Subject: Re: Best way to power array of LEDs?
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Date: Fri, 04 Oct 2002 06:47:26 GMT
NNTP-Posting-Date: Fri, 04 Oct 2002 08:47:26 MET DST
"Jerry G." schrieb im Newsbeitrag
> Each LED must have its own series resistor. Most of these LED's work
> at about 30 to 40 ma with about 1.6 VDC across them. You should be able
> to use a 320 ohm 1/2 watt resistor in series with each LED if these are
> in the spec range that I used as an example.
> LED's cannot be wired in parallel to each other being fed from one
> resistor. They can not also be wired in series with each other.
Nope, of cause they can be wired in series if the available voltage allows
Check the datasheet for the typical forward voltage. Red leds have around
1.7V, yellow/green ones are 1.9-2.3V, blue/white ones even higher 3.2-3.8V.
If you use just a resistor in series with each chain, you should calculate
it for the max. supply voltage which I would suggest is 14.0V.
Now if you put 6 red leds in series with 20mA current rating, you get
6*1.7V=10.2V; 14V-10.2V= 3.8V; 3.8V/20mA=190 ohms; take 180 or 200 ohms. The
resistor can be a normal 1/4W 0207 type.
electronic hardware designer