Efficient Parallel LED Circuit Design

LED Forum members,

I am looking for an efficient parallel circuit to power 3 to 5 (5mm) LEDs using three or four either AA or AAA batteries, and I need to be able to go from OFF, to LOW, to MED. to HIGH, as well as STROBE. Anyone have such a circuit, suggestions on building such a circuit, or have ideas on where I can acquire a circuit like this? I greatly appreciate your input.

Thanks so much,

Scott Schultz
[email protected]

Howdy Scott,

Sure. How about the WorldTorch DIY kit . This is the circuit I used for Scott's 'Milky Candle'. You'll have to supply the switch, but all the other parts are there for a single LED with low/medium/high steps of roughly 2, 8 and 32 mA. I think you'll find that you need roughly four times the current per step to make enough difference.

In your case, you want to drive to higher currents, so I'd keep the medium and high current resistors that come from the kit, use them for low and medium and add the proper resistor (You're looking for half an ohm or so) for the new high. 8, 32 and 120 mA for low/medium/high. The instructions for multi level switching are elsewhere on the home site. 120 mA is getting to the top end of what you want to do with the supplied transistor (2N3906), but I think it should suit your needs nicely.

Four bucks, shipped (to the US). If you want to hold off a little bit, we just got some printed circuit boards made that we're checking out. We'll no doubt have another kit in the same price range using them soon (assuming the boards work out as expected). There's also a high current version in the works (suitable for driving Luxeons).

Details of all this good stuff can be found elsewhere on the WorldTorch site. Schematics, circuit descriptions, photos and so on.

Anyway, I think that solves your basic issue. "Strobe" can fairly easily be added a number of ways. I assume you mean you want to flash the LEDs at full current?

Doug Owen