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Old 29-04-2012, 14:38   #1
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A bit off topic electrical question

I'looking to make a seriously bright torch. Its gonna be an over the top umbilical diving torch. so it doesnt need to be focused, but needs a good spread.I'm thinking using something like this 8000 Lumen led.




DC Forward Voltage (VF): 32~36 Vdc
DC Forward Current (IF): 3000~3500mA
Viewing Angle: 140 Degree
Color Temperature: 6000~6500K
Intensity Luminous (Iv): 7000~8000LM

at the moment I'm thinking of powering it with a sealed lead acid batter 12v. So ill obviously have to step up the voltage to 36 or so volts. I'm only looking for about 1 hour battery life so Ah shouldnt be a problem.

My question is, what is the best device to use to step up the voltage?
this?
http://www.ebay.co.uk/itm/DC-DC-Conv...ht_2864wt_1392

Also does anyone think this build would be a bit unrealistic?

Thanks for any help.

Paul
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Old 29-04-2012, 14:57   #2
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Re: A bit off topic electrical question

Youd be better off ganging up a bunch of NimH batteries, and build the whole thing into a PVC pipe with a clear end, and a magnetic latching switch, operated by an external magnet.
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Old 29-04-2012, 15:04   #3
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Re: A bit off topic electrical question

Paul, I'd suggest doing some reading on LED design issues first, or you're going to have expensive toast. LEDs are easily given excess amperage, just as important as the correct voltage, and either one will overheat them. They're heat sensitive, so proper heat sinking is also critical. And like all light sources for dive lights, you can pick a point on the performance curves and run the "bulb" at a point where you will reduce the life expectancy (typically 50,000 hours for LEDs, possibly less for this one) but increase the light output. Commonly done with dive lights.

The ebay listing has been removed, so I can't comment on that.

I'd suggest using a 36v battery pack (three small 12v lead acid cells would do nicely) and then using a current regulator for the device.
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Old 29-04-2012, 15:11   #4
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This really needs a constant current drive.

Dave
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Old 30-04-2012, 15:54   #5
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Using a 12V battery, we're talking about 10A. For an hour, the battery should have 30~40 Ah capacity.
Isn't?
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Old 30-04-2012, 16:13   #6
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Re: A bit off topic electrical question

Assuming one 12v battery and a voltage tripler with zero loss. But batteries in dive lights have to be portable, and it is more likely a 12-17Ah battery would be used and simply deep cycled, as few dives last more than one hour and having a lighter load counts more than battery longevity for most divers.
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Old 30-04-2012, 16:29   #7
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Re: A bit off topic electrical question

7000~8000 lumens is a lot of light. 3000 lumens not enough? If it was, battery would be a simple 3.7 volt lithium. I have a custom built light at 3000 lumens, good flood, and by far the most illumination I've held in my hand.


This shot was with a 20 watt quartz 6 volt lantern style flashlight.


Same exposure, using the LED flashlight.


This is overkill, but maybe that is what you want, another one off build.




Normal $250 store bought LED.


The one off creation.
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Old 30-04-2012, 17:05   #8
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Re: A bit off topic electrical question

Bob-
You may already know this, but "lumens" can be misleading. From the Wiki: '
The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. Mathematically, 1 lx = 1 lm/m2."

IOW, that LED is claiming 7-8000 lumens across 140 degrees--which is one hell of a wide spread for that much brightness. Maybe 10-12x more than the typical "flashlight" beam, considering it goes by square not linear spread.

Or he might be planning to cook fish with it.<G>
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Old 30-04-2012, 17:14   #9
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Re: A bit off topic electrical question

That emitter is 100 watts, so should produce light output that comes close to matching a 1000 watt incandescent, by the rough rule of thumb that a CF is about 5X in light at same wattage, and LED are close to 10X.
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