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Anyone know anything about electronics?

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fraktal

Member
Oct 26, 2007
31
0
Right, it's a long shot, but for a hair-brained scheme I'm going to build a huge bank of ultrabright LEDs. These will all be soldered to a PCB and powered by a spare computer PSU I have kicking around...but I don't really want to solder 790 voltage limiting resistors as well! (the fumes would probably damage my IQ and I don't have enough spare.)
Anyone know if it's possible to use one resistor (or an handful) instead of loads to limit the voltage from 5v to 3.6v, if the LEDs each use 30mA?

(for a hint as to what I'm attempting, try here!)
 

fraktal

Member
Oct 26, 2007
31
0
Wait...if I connect the anodes to +12v and the cathodes to +5v with two leds in series, that'll give 7 / 2 = 3.5v over each LED, right?
 

Steve Sharp

Senior Member
Dec 3, 2007
114
1
Underground
That's pretty good thinking, don't think I would have come up with that solution. I see no reason that it won't work. Computer Power Supplies have a common ground among the outputs, so you truly would have 7v difference, which would be split evenly across the two series LEDs. Since current is the same everywhere in a series circuit, that won't be an issue. :rolleyes:

I'm betting it will work, just haven't ever seen a circuit like that before.

:)