900 lumens regulated LED rock or roof lights

[paddlenbike]

I have built drivers based on three different linear circuits and they can range from semi-efficient to totally inadequate. If you can drive a LED (or series of LEDs) without relying on your integrated circuit to drop a bunch of voltage/amperage, a cheap linear circuit will work just fine. In other words, if you run three 3.3V LEDs in series (9.9V total) from 12 volts, you are only dropping 2 volts at the regulator. However, try running one 3.6V LED from a 14.5V car battery running at 2.2 amps and you are now dropping 10.9 volts x 2.2 amps or 24 watts. That is a totally unreasonable amount of heat to ask a small LED circuit to dissipate. So, my experience tells me to match total LED voltage to your source voltage and run them at lower amperages if you want to use a home-brew circuit. Otherwise, you're stuck with buying a more expensive DC-DC switching regulator.

[glenyoshida]

Glen, have you used the P7 yet?

Looks like one can get the emitter and heatsink for about $20. Being one who likes to build things from scratch, does anybody have any instructions on building a driver that can handle that much power?

No, I have not used them yet other than a unit in my flashlight. It's not real high on my priority list but it sure will be a fun project later. I think I'd like to get my gas tank skid done as well as some other armor first.

[glenyoshida]

I have built drivers based on three different linear circuits and they can range from semi-efficient to totally inadequate. If you can drive a LED (or series of LEDs) without relying on your integrated circuit to drop a bunch of voltage/amperage, a cheap linear circuit will work just fine. In other words, if you run three 3.3V LEDs in series (9.9V total) from 12 volts, you are only dropping 2 volts at the regulator. However, try running one 3.6V LED from a 14.5V car battery running at 2.2 amps and you are now dropping 10.9 volts x 2.2 amps or 24 watts. That is a totally unreasonable amount of heat to ask a small LED circuit to dissipate. So, my experience tells me to match total LED voltage to your source voltage and run them at lower amperages if you want to use a home-brew circuit. Otherwise, you're stuck with buying a more expensive DC-DC switching regulator.

Great info man! Thanks for posting up. Makes a lot of sense.

[glenyoshida]

I talked to a local shop that specializes in rebuilding alternators for trucks and plows and such. Knowing little about alternators other than the basics I was surprised to learn that upgrading the stator to a high amperage output might be at the cost of low RPM alternator output. The tech there was saying that I might get less output at Idle than my stock 80amp. Just like every project there's always something to make things more interesting.