lk20425pc -> controlling leds - help me please

eatmorepossum · Post by **eatmorepossum** » Sat Apr 12, 2003 7:31 am

I realize this is a rudimentary question but I couldnt find any posts that answered such a simple one.

Please explain how to hook up an led to a high power gpo such as the ones on the lk20425pc. I have added 510 ohm resistors to the connections and still smell stuff burning (mosfets?). Plus it killed all my led's but 2 right out of the gate.

Does it matter where the resistor goes in the circuit? Is 510 ohms the correct resistance? Why did two not burn up? Which side of the gpo's is positive and which is ground? Why isnt this marked???

Now that i'm in the market for new led's can someone suggest what kind to buy at radio shack or otherwise.

Some guidance here would be appreciated. I've already killed a vfd and would like to get this lcd working or at least not destroy it.

Post by **Cheese** » Sat Apr 12, 2003 2:35 pm

It depends on your LED's but using http://www.bit-tech.net/article/68/ I get a resistor value of around 400 ohms for your average LED - so 580 should have been fine.

You need to wire the resistor in series i.e. one resistor leg to a gpo pin, the other to an led pin and then the final led pin to the other gpo pin - aside from that it doesn't matter where they go int he circuit.

The display's manual will tell you which pin of the GPO is positive and which negetive, if they really aren't marked on the PCB then it's bad design (I don't have a -PC to check).

I hope that burning smell was your led's popping, if you really have burnt the transistors on some of your high power GPO's they won't work anymore...

Rob.