help!!!!!

Thread Starter

Dandiaz

Joined Apr 8, 2014
1
new to the site thank you; I constructed a led sign COCKTAILS having a
major problem burning up leds. using a pc power supply 3.8 vdc 18Amp
uln2003a each letter uses 50-80 leds can someone help.
 

djsfantasi

Joined Apr 11, 2010
9,156
Schematic, schematic, schematic! Go to advanced mode and attach your images. Note that LNG is preferred; jpg files are blurry.
 

MrChips

Joined Oct 2, 2009
30,720
help!!!!!

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My crystal ball doesn't see a resistor between each LED. A LED is a current driven device,

So, the series resistor is R= (Vsupply-Vf)/Iled

The last term is I led. Vf is the NOMINAL operating current and is generally different for each color.

The wattage of the series resistor is > I^2*R

The larger LED lamps use a currrent regulator which makes the light output less sensitive to temperature.

Oh, you can string the LED's in series. You just have to total up all of the nominal forward voltages.
 
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