Quote:
Originally Posted by billbo911
I believe the 2N3904 may be a little under rated for this unless you use one per leg of your circuit.
Alternatives are: the IRL3103 MOSFET (One of these can handle the entire circuit without breaking a sweat. It's continuous drain current rating is 40A.) and the ZTX603 Darlington (continuous current rating is 1A).
If you can get the IRL3103, you will be in good shape. The ZTX603 is lower rated, but will do just fine if you do the math right.
So, for the math:
What voltage will be driving this beast?
What is the Vf of each LED?
How much current does each LED require to turn on fully?
Find this information out and the math is as simple as E/R=I.
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I was looking at the 2N2222 which seems to be the same as the 2N3904 except rated at 1A but I will definitely look into the suggestions you made.
I designed the circuit for a plain 9V battery. All the math works out for 1.5V, 100mA LEDs but I'm going to see if I can make it even less power-consuming. The Vf for the LEDs will be either 1.5 or 1.2 with a forward current of either 100mA or 20mA. My first choice would be the 1.2, 20mA LEDs but I need to see if I could get them delivered before our team goes to Atlanta.