# I want to make a different kind of flashlight with ordinary LEDs for emergencies



## Chuckt (Nov 7, 2011)

(I'm approaching this from an electrical, electronic, microcontroller perspective. I want to build something new.)

I went through hurricane season last summer and I remember being in the hardware store and there were probably at least six people in line at any one time looking at sump pumps. Most stores were sold out of flashlights for a week or two except for the most expensive flashlights.

We lost power but we were fortunate that we were only without power for about six hours. Our area has a limit on how much rain it can accept. Some people easily lost power for half a week or more. We have flashlights with the lantern batteries and I have some flashlights that take double A batteries. 

I began to think about our needs and when the flashlights were back in stock, I bought a few more flashlights. Since we have rechargeable batteries and (double AA) batteries are in abundance, I bought a couple more flashlights that use double A batteries and one of them has an LED in it. I have two other LED flashlights with multiple LEDs in them. The problem is that they aren't bright enough and the LED flashlight says it will operate for about seven hours.

I'm approaching this from an electrical, electronic or microcontroller perspective. What I would like to do is have a flashlight that can switch from the number of LEDs it uses from low to high and I would also like to have this flashlight work with a 6 volt lantern battery. I want it to be able to provide a lot of light and also be able to last a long time because LEDs use less electricity than regular bulbs. I want to be able to switch from low to high brightness and also be an energy saver in case we need a flashlight for a couple of days.

The kind of flashlight we have to convert (in abundance) is here (you will have to copy the whole link as it all isn't underlined). It is basically an Energizer flashlight with a 6V lantern battery:

http://www.lowes.com/pd_355538-346-...currentURL=/pl__0__s?Ntt=flashlight&facetInfo=

Or should I just buy this flashlight:
http://www.walmart.com/ip/Dorcy-13-LED-6V-Volt-Lantern-with-Battery/17351562
Some of these flashlights are only 40 lumens even though they use 19 LEDs:

http://www.walmart.com/ip/Hoffco-08-N104-PL-Norlite-19-LED-Flashlight-Platinum/16480853

Should I bother with this project or just go out and spend the money on a good flashlight? Can I do this with some resistors or do I also need to use a chip? If a good design is created, it could radically help others and it could also be a best seller. I was hoping for 100 lumens in a flashlight from regular LEDs.

This flashlight has 52 LEDs:
http://www.walmart.com/ip/Trademark-Global-Super-Bright-52-Bulb-LED-Flashlight/17155395
I found these other projects on the web that are sort of like what I want to do so they may give me ideas.

Lantern Torch LED Conversion
http://www.instructables.com/id/Lantern-Torch-LED-Conversion/

How to Make an LED Flashlight
http://www.popsci.com/flashlight
Honorable mention:

The universal multicolour torch (flashlight)
http://www.instructables.com/id/The-universal-multicolour-torch-flashlight/

This flashlight has 500 LEDs and isn't something I'm going to build:
http://hackaday.com/2010/03/26/thats-a-big-flashlight/


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## xul (Nov 7, 2011)

Chuckt said:


> a flashlight that can switch from the number of LEDs it uses from low to high
> 
> have this flashlight work with a 6 volt lantern battery.


You need a current source.

With LED voltages at >2v and more three LEDs you need a convertor that goes from 6V constant voltage to a current source that sources the recommended LED current, assuming each LED is identical. 

Decide on your max number of LEDs.

Of course, battery watt-hours > LED energy consumption.


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## eh4 (Feb 19, 2012)

dimension engineering has an up/down switching regulator called AnyVolt3 that weighs about 1.5 oz and can supply 3 amps out at 3-24volts from 5-30 volts in, costs about 50$.
they also have a some nice, tiny step down switching regulators that give 1.5 amp out and a little boost converter that will deliver up to 1.5A at 2.2-5volts. -those run around 25$.
I'm sure there are cheaper ways to do it but these are plug and play, ready for breadboard.


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## jellydonut (Mar 3, 2012)

I would recommend regulating the amount of current going to the LED rather than using a ton of LEDs and switching them on and off. LEDs get more efficient as less current goes through them, so a single LED working at very low currents would be more efficient than a swath of small LEDs working at the higher end of their operating curve.

In that case, buying an off-the-shelf light with adjustable output would be better and easier.


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## Norm (Mar 17, 2012)

Test bump


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