Is 4 * 1W LS equal to 1 * 5W ?

I'm curious about this because in another thread, someone posted that the 5W is essentially 4 of the 1W dies put together.

If it is 4 1W dies, could I achieve similar output if I used 4 of the 1W LS and used a larger collimator to focus all the light? (Similar in terms of lux and then similar in terms of candela, ie number of photons and concentration of photons.)

Apart from the larger mounting area needed, what are the pros and cons of making such a light? Material costs, power consumption, etc.?

Hiya Jeff! Enjoying those trasers, I hope?

It is quite true - the 5W is made up of 4 1W dies arranged in a paralled-series configuration, thus explaining the 2x voltage and current.

You could quite easily get the same, probably more light from 4 1-watters than you would from a single 5W, reasons being efficiency and thermal management. The problem with using 4x 1-watt is the size and complexity of the package, and very likely the optics too, since you will need 4 collimators - one will not do.

4 single watters will cost you more as well. One other problem is bin matching. Its gonna be hard buying 4 well-matched luxeons unless you buy them by the reel, or the mounted ones in qtys. The mounted ones are made in 4x4 arrays using bin-matched luxeons, so if they're side-by-side each other on an unbroken array - you can be pretty sure they're matched well (if you flip over a mounted luxeon like the Star/O you'll see the binning info printed on the back). Other problems I can think of:

- uneven lumen depreciation among the 4
- uneven color shift among the 4
- difficulty in perfect optics alignment

The single biggest advantage of using 4 1-watters instead of a single 5W is thermal management. The 5W allows you a max metal-core pcb temp of 75C so that you don't broil the die to death. Because of the lower heat density in the 1W, these fellas will allow you a max metal-core pcb temp of 105C - a whopping 35C increase in headroom!

Hotfoot:

Very well said -- clearly encompasses and summarizes all I've read on the topic.

Originally posted by lemlux:
Hotfoot:

Very well said -- clearly encompasses and summarizes all I've read on the topic.

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<font size="2" face="Verdana, Arial">Ditto!

Dan

The 1w LS is 1.25w.
4x1.25=5

Is the 1w in the Arc LS overdriven (original version). How many "volts" is it designed to take without being classified as overdriven?

And yes, you can probably tell that I know nothing about this subject....I'm just curious.

Doesn't really matter bout volts, it's more about amperes... 350 milliamps... what whatever voltage necessary to drive it to 350 milli amps.

oh....ok....then back to my original question.

Is the 1w in the Arc LS overdriven (original version) with either the single 123 or 2 aa batteries in use? Or, is it underdriven or driven at spec?

If I had to answer with a single word - no.

Otherwise, I'd say:

AFAIK, the original Arc-LS was "conservatively" driven at or very near spec. Hey - it was early days then! At that time, no one made an LED flashlight powerful enough to get worryingly warm in your hand.

How bright your unit turned out depended hugely on the luck of the draw (ie. the batch of luxeons PG received from Lumileds at the time) and whether or not yours was classified as a factory first or second.

With the Arc LS original, you *could* "overdrive" the thing a little using 3 'N' cells, or any other combination as long as it was no more than 6V (the circuit's max rating). Of course, you'd blow your warranty and Peter was clear about that.

Because of the way LEDs usually react to changes in voltage, they are generally rated by current rather than voltage.

The 1w LS devices are rated at 350mA. For the red and yellow devices this takes something like 2.8 volts (plus or minus several tenths of a volt), and for the green, blue, and white devices this requires something like 3.3 to 3.6 volts. In order to feed more current to the device, you need to raise the voltage, but again the voltage needed will be different for each device.

IMHO anything more than 350mA is 'overdriven', but with good heatsinking people have driven the LS 1 watters to more than an amp. However, please see http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=14;t=000684 . There is little reason go much beyond 500mA if this data is correct.

-Jon

Originally posted by Nerd:
Doesn't really matter bout volts, it's more about amperes... 350 milliamps... what whatever voltage necessary to drive it to 350 milli amps.

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<font size="2" face="Verdana, Arial">Nerd, that is not quite correct. While LEDs are indeed current-based animals, if you are taking this in the context of power calculations for luxeons, voltage *does* matter.

Don't forget that luxeons are binned, amongst other things, according to forward voltage, which may reach as high as 3.99 volts before it'd light up. Some luxeons will glow even way below 3 volts, particularly the reds and ambers. Point is - if you drove a luxeon with 2 volts at 350ma, its not likely to light up.

Remember too that 350ma is a nominal (and recommended) current drive rating as well and is not a hard and fast rule.

Hi Hotfoot: Thanks for the Trasers. I have a couple of the greens hooked on to my "emergency" lights and I've set a couple away for gifts. Very cool. When we meet again, if I should forget, don't hesistate to remind me to pay you. I know we asians are a little "touchy-feely" about asking for money from friends, but I sure as heck don't want to stiff you.

Light-headed: Sent a couple of emails your way. Can you check and reply? Thanks.

Thanks for the answers everyone. Pretty much what I expected. So LEDs haven't gotten much more efficient than the Luxeon Star 1W design. And we have heat problems to boot, although driven at 350mA, it doesn't generate as much heat to be a serious problem. (Isn't the heat evidence that it isn't as efficient as it should be?) And there is such a huge variance in power requirements, needing between 3-4V and 350mA to run.

I'm guessing that since these are current driven devices, I can line up 4 LS in series and lay 12V across the terminals and expect all 4 to find their own best voltage but all run at approximately 350mA? And will they all deliver similar levels of illumination if powered like that?

Originally posted by Light-Headed:
oh....ok....then back to my original question.

Is the 1w in the Arc LS overdriven (original version) with either the single 123 or 2 aa batteries in use? Or, is it underdriven or driven at spec?

Click to expand...

<font size="2" face="Verdana, Arial">The original Arc-LS were designed to drive the LS at 350mA. However, the circuit was apparently a voltage-controlled type, so with the variations in the LS foward voltages, there was quite a lot of problems with the Arc-LS (which is also why there were so many more seconds as they had problems and had to be returned for tweaking or repair).

The hybrids that everyone is talking about these days apparently have a new circuit that is current-controlled, so that it doesn't matter if the forward voltage of each LS varies between 3V and 4V. The hybrids were driven first at 500mA, and then brought back to a slightly more conservative 400mA. The heat generated at 500mA was just too much. The heat generated at 400mA was more acceptable. Again the problems of brightness versus efficiency and non-destructive running conditions.

The LS rev2 uses the new current controlled circuit set to drive the LS at 400mA. The differences between the hybrid 400mA and LS rev2 are in the physical head, not the circuit. The hybrids used the new circuit but the old, 2-piece, head.

Hope I got that right.

Originally posted by hotfoot:
Don't forget that luxeons are binned, amongst other things, according to forward voltage, which may reach as high as 3.99 volts before it'd light up. Some luxeons will glow even way below 3 volts, particularly the reds and ambers. Point is - if you drove a luxeon with 2 volts at 350ma, its not likely to light up.

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<font size="2" face="Verdana, Arial">Quite true, but the point is that with a Luxeon binned to 3.99V, you _couldn't_ drive it at 2V and 350mA. It isn't as though you could apply 2V to the device, and 350mA would flow through it. Instead, if any current flows you will get light (in relation to the amount of current flowing), but you need to reach sufficient voltage to get the current to flow in the first place.

It is true that you need to consider voltage to get the power calculations correct; and if you have a Luxeon binned to a lower voltage then you will both get more light with a fixed voltage source (eg a pair of AA cells), and I'd bet that you could drive it harder (since the lower voltage would mean less power dissipation at any given current level.)

-Jon

Well put, Jonathan! I kinda flubbed over that explanation a bit. That's what they mean by forward voltage - ie. to overcome the LED's "inertia" so to speak. What I meant to say was if you drove with a power supply that was capable of delivering that 350ma, you'd still need sufficient voltage to realize activation and function - whatever the current requirement of that LED. Thanks for clarifying things.

Originally posted by Steelwolf:
I'm curious about this because in another thread, someone posted that the 5W is essentially 4 of the 1W dies put together.

If it is 4 1W dies, could I achieve similar output if I used 4 of the 1W LS and used a larger collimator to focus all the light? (Similar in terms of lux and then similar in terms of candela, ie number of photons and concentration of photons.)

Apart from the larger mounting area needed, what are the pros and cons of making such a light? Material costs, power consumption, etc.?

Click to expand...

<font size="2" face="Verdana, Arial">I just put 3 of the 1W emitters into a StarLux, direct drive. Each emitter pulls about 500mA in this setup, so they are not overdriven too hard. Is it brighter than a single 5 watt? I don't know.

Three 1W emitters are definatle bright! Seems comparable to the cyan 5W flashlights I've made. I measured 1170 lux. That is not a tiny hot spot, but a huge flood of light.

See the post on the StarLux TripleStar.

Wayne J.
www.elektrolumens.com