[billbo911]

Originally Posted by bobabot1

I am trying to rig up an LED array for my team but so far, I'm having some troubles. I want to make a 20 IR LED array but I know the transistor I will need to use to boost the signal voltage of the remote I'm using. Here's my schematic thusfar (sorry for crude ASCII drawing. -|>- is an LED and -/\/\/- is a resistor. The circuit is four parallel groups of five LEDs in series)

+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 15 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 15 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 15 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 15 ohms

I've heard that I can use a 2N3904 transistor. Would that be what I'm looking for?

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.