Noob questions...

Ok, I've got a hold of a cree xre.. trying to confirm my understanding of components and get some opinions before I start making connections.

That being said... downboy and badboy converters. The step up converters are for boosting and holding a constant feed to the led, and the step down converters are for limiting and holding constant feed.... correct?

In your opinion, which is more beneficial to use?

Also, direct drive, should I stay away from?

much thanks for any help

-Gjm6syn6

Welcome to CPF, gjm!

You're correct about what the converters do. "Beneficial" though, may be the wrong term to use. It's more a matter of the design of a particular light, where a boost circuit would be used mostly in small lights running one or two small batteries where the voltage needs to be brought up to properly power the LED, and a buck circuit is great for when the voltage from your batteries exceeds the Vf (forward voltage) of an LED. Both will regulate current unless forced to go out of regulation... meaning too much V into a boost, or not enough V into a buck. In either case, the circuit just goes into direct drive... speaking of which...

Direct drive is just fine. It's actually the most efficient, as there are no losses to a regulating circuit. The only downside is you'll have constantly dimming output as the batteries drain. If you have a close match between batteries and LED Vf, you can many times just run it straight. If there's too much current, the appropriate resistor is all you need.

What kind of light are you looking to make?

Thanks for the reply, I currently have several options... several maglites sitting around... a large amount of plastic "walmart specials", and a few cheap tac-lights. Right now I'm leaning towards an old gutted dorcy... I believe it had a luxeon of some sort in it originally. So, something relatively compact that's got somewhat of a range on it.

I figured direct drive was ok, but I have easy access to a wide variety of batteries (work in a camera store) and I'd rather be running off of whatever lasts the longest. Prolly cr123s.

This will be my first go at a usable flashlight...(something other than a film canister with leds poking out of it) lol

I appreciate the help, if you have any recommendations I'd love to hear them.

Thanks,
Gjm6syn6

You have a film can with LED's poking out?! Pics, please!... hehe. I LOVE cheap mods using household items!... or camera store items as it were.

Hmmm... there are soooo many different directions you could go in, it's hard to make a recommendation offhand. But, to use 123's you'll need a host that fits them, which excludes using a Minimag and other metal AA lights. You might be able to open the inside diameter of a plastic Dorcy a bit though. 3 123's are just a few millimeters longer than 2 AA's, so with a little tailspring shortening, 9V through a buck converter to a single Cree would give some serious runtime, drawing lightly from the batteries. Two 123's and a dummy cell would also work. However, without some kind of cut-off or low voltage warning, over-draining 123's is not recommended for safety reasons. You'd need a driver that lets you set warning flashes at a desired voltage level... like a bFlex from TaskLED. BTW, AMAZING freakin' driver.

All that said, I'd recommend using AA size batteries, be they Alkaline, NiMH, or Li-ion. Much easier getting them into most small lights (some dry, flashaholic humor there), and more mAh than 123's. If your Mag's are D size, the options really open up. It boggles the mind what one can do with a D size Mag. It'll also boggle the mind to see how quickly a flashlight can drain your wallet.

Some more detail is probably needed. What's the intended use for this light? How much do you want to spend?

Edit: Heatsinking is also major factor to maintain brightness and LED life... forgot to mention that.

LOL, I can one up the glowing film canister. This is the byproduct of a disposable camera, hi-8 to vhs converter motor, a cheap flashlight, and nothing to do at work.....

http://s25.photobucket.com/albums/c96/gjm6syn6/?action=view&current=IMG_6054.jpg

and running

http://s25.photobucket.com/albums/c96/gjm6syn6/?action=view&current=IMG_6060-1.jpg

lol...that was a slow day.

Hmm, the dorcy light is metal, and actually larger than enough to fit cr123s in, could probably get two in there with some tailcap modification. Would one AA in that even be worth the trouble? The three mags I can find are a mini, two C cell, and a three D cell.

Intended use...well....just about everything from crawling through water drainage tunnels to wandering around abandoned power plants. Seriously.

http://www.southcarolinaghosthunters.com

I've had some serious problems with dying flashlights over the years.

I think I'd probably spend up to fifty or sixty bucks right now. But like all things, it'll most likely end up in the thousands over the next few years. lmfao

-gjm6syn6

gjm6syn6 said:

Intended use...well....just about everything from crawling through water drainage tunnels to wandering around abandoned power plants. Seriously.

http://www.southcarolinaghosthunters.com

I've had some serious problems with dying flashlights over the years.

I think I'd probably spend up to fifty or sixty bucks right now. But like all things, it'll most likely end up in the thousands over the next few years. lmfao

-gjm6syn6

Click to expand...

Allow me to make two assumptions:
1) Runtime is an important consideration
2) You don't have a headlamp

If I were limited to one light and one light only, I would keep my Princeton Tec Apex headlamp, which runs on 4xAA. Especially wandering around an unknown place, I like to have a headlamp and a hand-light. My Apex is modified with a Seoul P4, a very easy mod that requires the emitter, solder + iron, and some thermally conductive paste. I believe others have done it with the Cree like the one you've already got. More info on that lamp and links to mod info here.

As far as a hand-light for searching unfamiliar places with, I'd say you need a combination throw light with some useful spill. CR123a-powered lights are good, but experience on CPF has demonstrated that a better way to run a bright LED for a long time is an 18650 like sold by AW in this thread. If you're considering a mod, especially because you seem to be a pretty capable guy at making things, it might be worth considering a 1x18650 or 2x18650 configuration. Obviously, you'd have to use a step-down converter for the 2x18650 config, and either direct-drive or buck-boost (I think?) for the 1x18650 setup. I've got a Lumapower M1 Hunter which runs on 1x18650 and on high mode it runs for 4 hours @ ~130 lumens, and something like 27 hours on low @ ~20 lumens.

Of course, if you want lots of power and runtime with alkalines or NiMH C or D cells, you could just pick up one of these from Gene Malkoff.

P.S. If you like silly and fun mod homemade lights, check out this thread, it's hilarious!

Bimmerboy said:

You have a film can with LED's poking out?! Pics, please!... hehe. I LOVE cheap mods using household items!...

Click to expand...

Hmmm, maybe I should have take some more pics of my toilet roll torch I made a couple of years ago. 6V, 12 x white LED array, 4 x AAA NiMH. All I can find now are some beam shots though, and that's pretty uninspiring considering the blue tinge...

Daekar - The headlamp is a great suggestion for the intended use. BTW, I clicked on your link to the fun mods you mentioned, and it was my thread! I'm honored, and thanks!

TorchBoy - If you post pics of the toilet roll mod, you MUST tell me about it!

gjm - If you really like 123's, something very nice in the price range you mentioned might be an Inova T3, or for even a few bucks less, an XO3... same light, slightly different housing. Both are tough, reliable, and with high build quality.

And, after seeing your whirling cat toy, I'd say save the Cree for when real inspiration strikes!

whirling cat toy...

first time I set it off in the house, I turn around to see my cat backing up in horror. lol

daekar, I've already got a decent black diamond 4 led light driven on 3AAAs. That princeton tec looks really nice tho, think I may see one of those in my future.

the 18650 is one battery I have no experience with, will have to do some research on that one.

torchboy- being able to make anything using a tp roll is a true sign of ingenuity, mad props.

Though runtime is a definate issue with what I'm looking for, I generally have a box of batteries nearby...within 30 minutes walking at the most.. I'd prefer something that could pump enough juice to blind a person or animal if I come around a corner to hannibal lector or something. Lmfao. (why I went with a cree)

-gjm6syn6

btw, ferrero rocher mod should be on the packing list for any camping trip.

I just did another disk search Bimmerboy, and this time found some pics I took of it back in May 2004. Time does fly. I'll post them sometime.