Instructables

Need help understanding LED drivers

Ok, I'm a newb to electronics and i'm having trouble figuring something out. Inspired by Dan's instructable, I decided to try and build my own headlamp. However, I've run into a problem. I have no idea what LED driver to use. I'm planning on using three of these bulbs, at 3.7v each and a max wattage of 4. I know if I rig them in series, the LED driver needs to be at least 11.1V, but my question is does the wattage of the driver need to be 12? Or should I rig the bulbs in parallel from my power source, and have one of each of these rigged to them individiually? Also, advice on whether it would be preferable to rig them in series or parallel would be great. Any help would be greatly appreciated. Thanks in advance

The wattage would have to be 12. Ir would be 12 if they were in parallel too, but you never, ever run LEDs in parallel.

NEVER in parallel.
The Insomniac (author)  steveastrouk2 years ago
Thanks! May I ask why I don't want to run them in parallel?
The Insomniac (author)  The Insomniac2 years ago
Also, could I rig the LED drivers in series to get to the desired wattage? Or should I just get one really powerful driver?
One solution would be to use a supply for each bulb, and if you need to turn them all on at once, use 3 pole single throw switch.
The Insomniac (author)  Goodhart2 years ago
Wouldn't that basically be rigging them in parallel, then?
not if they weren't electrically connected. I believe I meant a 3 pole double throw switch...anyways, it could be rigged like some "breaker switch handles" that control 3 switches at one, or isolated but on the same switch. Which ever is most conveniant
The Insomniac (author)  Goodhart2 years ago
Ok, I think i'm understanding you know, sort of. As I said, i'm new to understanding electronics. Right now i'm trying to find the right LED driver, but I can't find a 12v 12w on the DX website. So could I use three of this set  to achieve the desired effect, in tandem with the switch? Unfortunately I can't seem to find a 3 pole double throw switch on the DX website, looks like i'll have to improvise(or try and find it cheaply somewhere else). I'm trying to build the whole project for <$35, hence why i'm trying to figure out different (read:cheaper)alternatives to the obvious stuff. Also, if it matters, I want the headlamp to have a low, high, and blinking mode.
You need a 12volt boost driver to do this
If you mean hooked up in parallel, then the voltage would not go up, but the amperage would. In series; the voltage does but not the amperage.
Get one driver who's rating = number of LEDs x wattage of EACH LED.
One reason would be that if one burns out or gets disconnected, the rest bear the brunt of the power, burning out more and more of them until they all are done.
They don't "share" current. When one LED takes more current, it gets hotter. When an LED takes LESS current it gets cooler. When its cooler, it takes less current.

So, when you have two in parallel, and one gets slightly hotter for whatever reason, it steals current from the other, which turns the OTHER down, while the hotter turns on HARDER

So it gets hotter......
Goodhart2 years ago
I couldn't find any "usable" specs on the driver. At the DX site.