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Old 04-12-2012, 12:00 AM
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Scorpius51 (John)
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Join Date: Sep 2009
Location: Canberra
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Quote:
Originally Posted by bloodhound31 View Post
Right, well, I did all that - only to find that adding the resistor dims all the LED's down to absolutely useless.

So, I removed the resistor and hooked it up to four LED's. Perfect and as bright as they were in the torch. Then I hooked it up to the remaining four that were in the torch also. Perfect again. Looks like the torch didn't need a resistor, so just because they are joined now via wires instead of a board, it seems it doesn't necessarily mean they need a resistor all of a sudden.
Looks like you are using 'white' (actually more blue) LEDs that have a forward voltage of ~ 3.5V. So you can probably run them in parallel without a current limit resistor. But, as Bojan stated earlier, you may limit their life. You will also drain you batteries more quickly. Perhaps you should use at least a 50 Ohm resistor (or 51 or 47 Ohm preferred values). If you're using the batteries in series (4.5V total), then you want to drop nearly 1 volt before dumping the rest across the LEDs.

Cheers
John
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