Newbie Needs Help -- cheap 1-cell LED setups

(Hoping I've gotten the right forum for this kind of question...)

Hello all... as the subject says, I'm fairly new to LED lighting, and VERY new to the idea of making my own, so please bear with me. I got started in all this when I became fascinated with an EternaLight from Technology Associates, in case any one wonders.

In any case -- I have a problem that does kinda run counter to the projects people seem to be working on here; if this sort of thing is old news, please point me to the relevant old threads... I've tried searching, but I suspect I don't have the right vocabulary in this area to find what I need.

What I want to do is to build some inexpensive (OK, *CHEAP*) LED lights to use on a club camping trip. I'd like to make a bunch of single-AA models for marking/illuminating trails, and a couple larger units of 2 to 4 LEDs (whether single-D or multiple-AA powered) for lighting the outhouses.

The reason for this is that the club currently uses candles in glass containers for this, which I consider to be (a) painfully low-tech and (b) a fairly significant fire hazard, and (c) high maintenance, as someone has to go around and light the blasted things. What I'm aiming for here is something that will run non-stop for about 96 hours. This way, they could be set up the first evening and not bothered with until we leave.

I first got the idea looking at the "Joule Thief" circuit at http://www.emanator.demon.co.uk/bigclive/joule.htm but quite frankly the idea of having to wind those ferrite beads by hand just doesn't appeal to me, especially considering how many of these I'd like to build.

So; here are my priorities. The units need to be cheap, almost disposable. They need to be reasonably easy to make, preferably on perfboard, as I've never gotten into etching PCBs. And of course, they need to run for (at least) 96 hours. (Some extra run-time would be nice, but not at the sacrifice of a lot of brightness during the main period.)

Any assistance is welcome, and I offer my thanks in advance.


George

Maybe you should consider modifying one of those solar yard lights. I've got one that I found for $6, basically it's just two rechargeable AAs, a solar charger, and a LED. They come with a relatively dim LED, but you could ad a brighter one. These will not run 96 hours, but will run the entire night with just one day's charge.

GeorgeM,
Welcome to the CPF! /ubbthreads/images/graemlins/thumbsup.gif If you want something basic that puts out a small amount of light and is basically disposable, you can get coin-cell LED keychain type lights. $20 for 20 of them. http://www.countycomm.com/light10.htm

If you want to use single AA batteries, it would require a boost curcuit and that would add to cost. You could get a few white LEDs on a perf board and drive them with three AA batteries and a variable resistor to adjust the output.

Luxeon 1 watt LEDs will run for days and gradually dim as time goes on. I have a Mini-LGI and ran it for two days straight in a hotel bathroom with 3 AAA batteries. It was bright enough after two days to not use the light! If you bought some Inretech Minimags with the Luxeon LEDs in them, load them up with Lithium AA batteries...they would run for 4 days with no problem. The Inretechs run $25 a pop. Another way to do it would be use "dummy" cells and wire in two Alkaline D cells so it would run bright for a week or so.

For single AA lights, pick up some CMG Infinity Ultras. The kids can throw them, drop them in water and kick em around with no damage. They run around $15 a piece if that is in your range and last 10 hours on a single AA cell. The Inretechs and CMGs are not disposable by any means, but they are relatively inexpensive and will last a lifetime.

Using one AA means you need a voltage boost circuit, which adds cost and complexity. I think it's simpler and cheaper to use multiple cells. You can use two AA's to run a red or orange LED or three AA's to run a white LED (the hotter colors need higher voltage).

If you really want to mark a trail for 96 hours on a single AA, look at the LM3909 LED flasher circuit. It will blink a red LED for months on one AA. It's fairly simple to hand-wire without any inductors or PC boards, but it does need a fairly large capacitor. Each blinker will cost a couple bucks for parts plus a few minutes of assembly time (you can probably get it down to a few minutes each if you make a bunch of them).

Finally, think about whether you really need to light up those trail markers continuously (even with a blinker). It sounds like unnecessary light pollution.

http://www.darksky.org

Ah... I see in my attempt to cover "everything" I left out some key points....

I'm interested in stuff I can fix in place -- to the ceilings of the outhouses, to trees along the paths. My tacky but (hopefully) practical idea was to drop each unit in a ZipLoc bag, and staple to a tree, for instance. This event draws 125-150 people, far too many to issue flashlights to, even if they are disposable. I've got several months, so building them myself isn't a problem. *Ideally*, I'd like to keep the price to around $5/each or less, if I can. (Yeah, I know, with the LED being $1 or more that's not easy, but...)

They don't have to be pretty, just functional. /ubbthreads/images/graemlins/wink.gif

George

The best idea is go to BIG LOTS and
get those Malibu Solar lights for 6 bucks.
Then modify them to your heart's content.
The lights don't need to work during daylight.
I bet you could come up with some great configurations.

I'm also trying to imagine 150 people wandering through the woods at night and NOBODY has enough common sense to bring a flashlight????

I'd love to watch this train wreck....<g>

I'd use 9V batteries with red 5mm led (bright) driven with appropriate resistor, plenty of run time, bright light. Elektrolumens has 9V battery holders for $2.50, just solder a LED and resistor to it.
Rob

Take a look here . You might find someting useful.

Decent LED's cost 20 cents or so. Really good LED's cost a dollar or more. We flashaholics on CPF like those because we're connoisseurs, but they're not really needed for what you're doing.

Really, I think step-up circuits are just not worth the hassle when even alkaline AA's cost 25 cents each or less.

Note that you cannot get 96 hours of useful continuous light from a single AA. There's just not enough power there. Use multiple AA's, or use D cells, or use a flasher circuit.

You haven't mentioned if you need a particular color of LED.

I think your best bet may be get some cheap 2D or 3D flashlights ($1.00 each at the local discount store around here) and replace the bulb with an orange LED and current limiting resistor (15 mA or so). The orange LED should run ok on two cells and you can use cheap (non-alkaline) D cells which are 25 cents each or so.

George,
http://www.superbrightleds.com/leds.htm The 10,000mcd newest, brightest LEDs cost $1.52 each in quantities of 10 to 49. Get two of those, a resistor and a 9V battery clip and you would have 20,000mcd lights for about $5 a pop. Put that thing in a plastic bag and it should be great. If you need all your lights to run for 4 days, run one LED from 3AA batteries (Rayovac 18-packs of AA are $5.96 at Wal-Mart)

The cheapest way to build them would be get those 10,000mcd white LEDs (~$1.75 each including shipping) a resistor (25 cents) a switch from Radio Shack ($1) a little wire, solder and some tape. Three Rayovac AA batteries are 90 cents. We are at $3.90 for your light including batteries. If you are really cheap, you could solder the wires directly to the batteries.

Elektrolumens sells 3 AA battery boxes with a switch for $4.00 each. Add the LED and resistor and you would have a light for $6 each http://www.king-cart.com/cgi-bin/cart.cgi
It would only be soldering the LED and resistor to the battery holder, very quick and easy to do. You could also tape the LED/resistor to the top of the box and throw it in the plastic bag. Heck, you could use epoxy and pot it to the top of the battery holder.

If it was me, I would go for the Elektrolumens 3AA battery holder/10,000mcd 5mm LED and a resistor. It should run easily for 4 days and with Rayovac batteries, costs about $7.00 each ready to go.

Flashing red lights sound great for paths. They can run the whole 96 hours no problem. How about 2 white LEDs for pottys and such? Just wire them to 2 D batteries. Disconnect durring the day. Re-connecting and disconnecting a few bathroom lights is LOTS easter than blowing out dozens and dozens of candles and re-lighting them every night.


Just because some of the lights will have to be turned off durring the day doesn't mean they ALL have to be turned off durring the day.

Hopefully not ALL the lights will get destroyed, but even if a couple do it's probably cheaper in the long run to use LEDs over candles...

*heh* I see your point... but that's not quite accurate.

Everyone *does* bring flashlights, the problem is that most trees tend to look much alike; it's useful to have some points of reference to assist in navigation.

And then you have the inevitable bulb failures (well, not me, everything I have is LED now /ubbthreads/images/graemlins/wink.gif, batteries dying (ditto /ubbthreads/images/graemlins/wink.gif, etc...

George

[ QUOTE ]
paulr said:
Really, I think step-up circuits are just not worth the hassle when even alkaline AA's cost 25 cents each or less.


[/ QUOTE ]

I've come to realize that... I suppose I was just taken with the idea of going really "high tech" to the point I somewhat lost sight of practicality. Spending several dollars on parts to avoid using 50 cents worth of batteries doesn't make a lot of sense....

I appreciate the reality-check.

If we're marking a path, why not use two cells and a red LED with a resistor? If you want flashing, that's cheap and easy as flashing LEDs are also very cheap.

I think a switch is a bad idea, something to go wrong and cost money. Put the cells in, when you put them up, take them out when you're done.

FWIW, some time back someone was selling surplus store POS attention getters, two cell AA holder and flashing red LED for two for a buck? You could easily solder up a pile of them in an evening.

Doug Owen

Doug's right, I forgot there are those flashing LED's which don't need any external circuit. I don't know what input voltage they need or how much total power they need. The LM3909 is cleverly built to use the timing capacitor (typically 200 microfarads or so) as a voltage booster so it can run on one cell. I used to build AAA powered LED blinkies into dead chemical lightsticks. The one-piece LED flasher should be simpler though, if you don't mind possibly needing multiple cells.

If I'm trying to save costs and not trying for ultra miniaturization I think I'd rather use two 5000 mcd leds at 20 cents each than one 10,000 mcd led at $1.52 /ubbthreads/images/graemlins/smile.gif.