Power a Luxeon Star with two AA batteries?

Build a switcher. There are lots of circuits available. Here is one:

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VCC = .8 to 3V ,---o---------------------. | | | .-. | C| 470R| |

You might want to check out

Streamlight makes a 2 AA Luxeon flashlight and a dimmable 3 AAA Luxeon headlight. I believe the flashlight has a DC-DC voltage converter, so it runs well on NiMH rechargeables.

"BruceW..1" writes:

has a infinite amount of information on flashlights and led's

In article , Robert C Monsen wrote: [...] I'm making a small change:

R2 gives Q2 a little protection. If a huge current tries to go through Q2, R2 will develop more than 2 diode drops of voltage and cut the "on" part of the cycle short.

It doesn't add many parts (one) but its protection is not all that good.

[...]

I'd use something faster for D1

This is a good idea. Over current spikes can slowly kill a transistor.

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kensmith@rahul.net   forging knowledge

The Linear Technology LT1618

Looks like a useful part for this application. Unfortunately like most switchers for portable applications it is only available in tiny surface mount packages.

It'll put out a lot more light at low average currents if you keep the peak current at 350ma.

For most of the SMPS chips available, they are significantly more efficient at a battery voltage of 2.4V, rather than 1.2V. You can probably get away with a step-up only device, 2 fresh alkaline AA cells won't provide enough current at ~3.5V to kill the luxeon device, even neglecting diode drops. Synch rectification will buy you a little bit, but not much.

What may also be useful would be a 3 cell device.

2 AA 1.5V cells, and 1AA 3V cell, for emergencies.

In article , Ian Stirling wrote in part:

I have found the efficiency of red, orange and yellow Luxeons to be maximized at instantaneous currents somewhat less, maybe around 200 mA. For white and blue ones, the efficiency is maximized at even lower instantaneous currents around 100 mA or less. If your average current is around or over 50 mA and the Luxeon is a white one, I recommend steady rather than pulsating current. But if the average current is only a few milliamps, then you are better off using pulses with a higher instantaneous current - perhaps 50-100 mA.

- Don Klipstein ( snipped-for-privacy@misty.com)

Zetex

have a range of single and double cell LED constant current drivers that are used in many commercial LED headlamps.

Dave :)

What's that Lassie? You say that BruceW..1 fell down the old sci.electronics.basics mine and will die if we don't mount a rescue by Mon, 06 Sep 2004 00:33:27 GMT:

Ask here:

Search in the electronics forum.

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Dan

Check candlepower.com or ledmusuem.com reviews before buying the Argo headlamp. One review alleged the 3 AA batteries lasted only an hour. Would be very costly, if NiMH rechargeable batteries weren't used. The new model Argo may have an improved (more efficient) driver.

What is the cost of building a LS 2-AA headlamp?

rechargeables.

Well, the 1W LS with lens, AKA -NW98, is about $16 or maybe a bit less. So I'd say that that's the most expensive part. You can also buy a kit of a LS and a Micropuck for about $25 and put into yout own case. I bought two of them from LED Supply and put them each in its own project box.

Micropuck:

df

sales:

Just make sure you heatsink the LS to some copper or aluminum.

In my humble opinion, the candlepower guys are a bunch of elitists, trying to make some bucks. They make these good looking flashlights, but they all use CR123 lithium cells which cost up to $10 each or more, and are hard to find. I think the only way to go is the two AA cells, and use rechargeables if you use it a lot. Two AA cells are only fifty cents on sale. See

What's that Lassie? You say that Watson A.Name - "Watt Sun, the Dark Remover" fell down the old sci.electronics.basics mine and will die if we don't mount a rescue by Thu, 23 Sep 2004 05:02:14 -0700:

You can get them for $1.00 at

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Dan