Crude little area light (pics)

[TigerhawkT3]

Once I realized that Vf varies with current and that DD won't necessarily fry your emitter, I learned that I could use an approximately 3V source (like a CR123A or two alks) to drive a Cree at around 150mA, for high efficiency and a huge unregulated tail. Since there are no driver circuits involved, I guessed that I could also double the voltage to 6V and use two Crees, for a simple doubling in output.

That's right, I only figured this out recently. Feel free to laugh.

So, here's what I did: I used one of those 4D battery carriers as the body, stuck a small piece of SS between the contacts, AAed a pair of Crees to it, and wired the thing in series. There's no switch. You pop in the cells and it lights up.

 

[Gunner12]

Re: Crude little area light

4D cells at 150 mA? That sounds like a long running light and great for longer blackouts.

I'm not laughing, I bet many of us have missed the obvious.

Do you have any pictures?

 

[TigerhawkT3]

Re: Crude little area light

Well, it's 150mA for each emitter, and at the batt's peak 6V. It decreases according to the graph in this PDF from Cree (page 6). Near the end of the batt's life, each emitter will be getting a small fraction of that.

At the beginning of batt life:
-Vbatt ~6V
-Vf ~3V
-Ibatt ~150mA
-Iemitter ~150mA*2=~300mA

At the end of batt life:
-Vbatt ~5V
-Vf ~2.5V
-Ibatt ~30mA
-Iemitter ~30mA*2=~60mA

Now I just have to think of a situation where I can use it. :laughing:

 

[nerdgineer]

Re: Crude little area light

If your LEDs are in series, then each one is getting the same 150 mA current, not 300 mA.

 

[Gunner12]

Re: Crude little area light

:kewlpics:

That looks like a pretty big heat-sink for 150 mA drive current. I don't think overheating will be a problem.

I think he means the battery drain is 300 mA.

 

[legtu]

Re: Crude little area light

I think he means the battery drain is 300 mA.

looks like the LEDs are in series so total current draw would still be 150ma.

 

[Gunner12]

Re: Crude little area light

Opps, my mistake. It would be 300 mA if in parallel at 3v.

 

[TigerhawkT3]

Yeah, I meant 300mA in total output. Each emitter is seeing 150mA, and the batt is pushing 150mA.

I probably could have just AAed the emitters right to the battery carrier, but it looks "different" this way.

Maybe I'll make some more of these with smaller carriers, like 2xAA and such.

 

[lexina]

Very simple and effective - I like it!

If you can wire in a small clicky switch and stick it beside the heatsink, that would make it even neater and you could leave the cells in all the time.

 

[TorchBoy]

Yeah, I meant 300mA in total output.

No, you don't. Really. It's the same 150mA going through both.

However the power is doubled. 3V x 150mA = 450mW. Two LEDs is 900mW.

 

[TigerhawkT3]

No, you don't. Really. It's the same 150mA going through both.

However the power is doubled. 3V x 150mA = 450mW. Two LEDs is 900mW.

Obviously, I wasn't clear enough. I meant:

There's one XR-E running at 150mA, and another right next to it. Two XR-Es, each running at 150mA. Combined with higher efficiency at lower power levels, that's slightly more light than a single XR-E running at 300mA (which, you'll notice, is the "total" number I mentioned).

I know it's using twice the power of a single XR-E running at 3V/150mA. That's obvious. It also has twice the output.

OK?

 

[Ken_McE]

Rough, crude, no concern for anything but brute efficiency - I like it! :naughty:

 

[TorchBoy]

Re: Crude little area light

I thought you were pretty clear.

At the beginning of batt life:
-Vbatt ~6V
-Vf ~3V
-Ibatt ~150mA
-Iemitter ~150mA*2=~300mA

At the end of batt life:
-Vbatt ~5V
-Vf ~2.5V
-Ibatt ~30mA
-Iemitter ~30mA*2=~60mA

:nana:

 

[scott.cr]

DUDE, that light is as crude as... crude hahaha.

Don't take that as a jab; one of my first homebrews was a chassis-mount lamp socket that I mounted to the plastic top of a beef jerky can. The wiring went down to a 1/8" headphone plug, which I plugged one of those multi-output "battery eliminators" into. This is when I first learned about overdriving incandescent lamps. It was a 4.5-volt lamp and boy was I amazed at the output when the battery eliminator was kicked to 12 volts!

Anyway, I like your effort. If you want some help machining a heatsink for your next crudity, drop me a PM.

 

[TigerhawkT3]

I had to solder something for school yesterday, and since I'm a procrastinator, I left it for nighttime. To prevent waking up the dog, I used my crude area light instead of the main outdoor lights. It worked well, but would've been better if I had had a good place to put it.

 

[Illum]

I had to solder something for school yesterday, and since I'm a procrastinator, I left it for nighttime. To prevent waking up the dog, I used my crude area light instead of the main outdoor lights. It worked well, but would've been better if I had had a good place to put it.

ever giving thought of buying a ABS enclosure from radioshack?
something flat, rectangular, drill too holes and install a clip, and learn to wear a hat with 4C cells clipped on to it. I once managed to do just that only was clipping two A2s to the rim and went biking at night...only once

 

[TigerhawkT3]

ever giving thought of buying a ABS enclosure from radioshack?
something flat, rectangular, drill too holes and install a clip, and learn to wear a hat with 4C cells clipped on to it. I once managed to do just that only was clipping two A2s to the rim and went biking at night...only once

Come to think of it, I do have a RadioShack enclosure just a bit larger than the 4D carrier, along with some styrofoam packing peanuts...

I can cradle it between my shoulder and neck, but I won't put 4D on my head. That's too much, even for me.

 

[Illum]

I can cradle it between my shoulder and neck, but I won't put 4D on my head. That's too much, even for me.

well since this ones epoxied down and all, not much you can do about this one...or I'd consider mounting a clip on the heatsink and use a hookup wire strand to separately stow the battery pack:nana:

either way it still looks awesome nonetheless:huh: