Driving 4 5mm LED's of 4AA's.

[Greg G]

This is a headlamp application. I've done a lot of searching this afternoon trying to find out what a good driver would be for 4 5mm Nichias but am lost. The power source is 4 AA's (6 volts).

I wouldn't mind having something with different levels, such as PWM.

Any guideance is appreciated.

 

[TigerhawkT3]

Wiring the LEDs 2S2P will make each one run at about 3V and 5mA (very roughly) on fresh cells. With four 5mms like that, I'd estimate 5-10L, 50-100h, and 1-2Ah out of the cells (alks, I presume) before you'd probably want to swap them out. It's not a battery sucker, but it's simple, cheap, and efficient. If you don't like the fact that it won't squeeze the cells dry, you can save them to use with a Joule Thief (almost as simple and cheap, much less efficient, but definitely a battery sucker).

 

[Lynx_Arc]

I just wire all 4 in parallel using a 10 ohm resistor if you have more than 4 LEDs to choose from I would wire up 2 AAs in series and wire the 4 LEDs in parallel and see how they match up in brightness and swap them out till they match because wiring in parallel the brightest get more current and the dimmest the least. After you get your LEDs chosen then go with the 6v and the resistor. I believe a 10 ohm resistor gives you about 25 ms drive to the LEDs depending on the Vf. I don't know of any drivers that have levels below 30ma for more than just the low mode but there could be some.