Battery operated LED light

Have a look through this thread.

BTW - I think you'll find most single-chip white LED's have Vf ≈ 3.5V. Blues are highest, at 3.5 - 5V, while reds have Vf ≈ 2V.

I think you'll find that if you string together 4 LEDs in series hooked up to a 12v supply you'll be doing OK. If they aren't bright enough, try groups of 3, then use a 10-turn pot to fine tune the current, or, use a 3 terminal positive voltage regulator, hooked up as a current regulator - all you need is 1 resistor or pot from the ADJ terminal to the OUT term, power goes to the IN term. Look at this PDF, page 9...

http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS009063.PDF

very stable and reliable current regulation with 2 cheap parts.

if you want to spend a little more, but have a lot better set-up, check these babies out...

http://www.fairchildsemi.com/whats_new/led_drivers_fan5607.html

PLEASE READ THIS!!!!

YES I'M SHOUTING!!!

Even with one of those LEDs at full current DO NOT under any circumstance look directly at the LED while it is illuminated! (Or even in a mirror)

We manufacture lamps with 20mA and 50mA LEDs. Any observation work is to use smoked glass and sunglasses for operator protection. We prefere to use video camera so that intensity is not "blinding".

Sorry to be so blunt, but I'd hate you to be so blind that you don't get the benefit of the light!

Are you warning about regular light emmitting diodes or LASER diodes?

Try this site, led.linear1.org/led.wiz. It is a tool to calculate an l.e.d. array, including resistor values and the serial and or parallel circuits that work best given the information provided. Really quite handy. Hope this helps!

Thanks to all for your comments and useful info. So, my calculations were all wrong. I will need some time for sifting through all the useful information given by you all. Right now, I am looking for -

1) A simple circuit which can work with may be even 15/20 bright 5 dia 20mA LEDs which I guess should be able to give me enough light, may be about 50 cd. I wish to see my own handmade LED light glowing soon. I will think of improving the circuit design subsequently to ensure that the battery does not get drained fast.

2) White LEDs of say 1000 to 2000 mcd which are of good quality and cheaper. I do not think these can be harmful to eyes. I checked and found out NICHIA has some LEDs with as much as 20000 to 30000 cd each, but I guess they will be quite expnesive. My worry is quality consistency for designing the circuit.

3) A simple circuit for recharging the battery at approx. 14V

H E,

1) A CREE 80 Lumen LED which has a runtime of 1.5hrs from a single AA cell is not a fast drain rate.

2) As the man said-DON'T look directly at it.

3) Your local battery supply store or electronics store will have chargers/or self assembly kits. You will have to decide if you really want a simple transformer powered unit or one of the modern pulse width ones. Ask them.

Cheers,

Stu.

HE,

I've read all the other replies and they do make sense, however, I use leds every day and the ones I use are required to be in series with a 100k resistor so that they don't fry on a 12v supply. No, they don't come with a circuit. Just the diode.

All sorts of colours, but I use red and white mostly.

Made in China.

Depends on what you want to use them for. Instrumentation? General illumination?

How many lumens?

I've also gone to the other end of the spectrum. Cree circuit driven diode will give 80 lumens/m from a 1.5v cell. Massive.

Need more information to be of real help to you.

Cheers,

Stu.

Thanks once again to all of you for comments and suggestions

Since I am a layman as far as electronic circuitry is concerned, frankly, I have not been able to understand most of your suggestions.

I guess you all have either over estimated by knowledge on electronics or you want me to work on it on my own. I was looking for a simple LED lighting circuit which now I will do it myself.

Again, all your suggestions will certainly come in handy for me. Thanks.

Bud,

Dissappointed that you got nothing out of your thread.

However it must be now apparent that you need to answer some of our questions so that we may fully understand 'where you're at'.

Please reply. Just tell us the answers where there are question marks.

For instance, we don't know if you even have a neighbourhood electronics store. Where are you located?

For my part, I'd like to help. I know all of the other guys share the same ambition.

I'm sure that there is no feeling in the community that you are required to go it alone, it's just that when you're talking to engineering types like most of us we often make the mistake that you know something of rudimentary science. I'm sorry !

There are a whole bunch of options you have in this arena and you need to tell us what components you have and where you'd like to go with them.

We don't have the time to teach you all you really need to know in the realm of electronics ( I've been at it for 65yrs and still don't know enough), so sometimes you may be better advised to access specific knowledge from other sources. Don't be insulted. Take the advice in the kind spirit in which it offered.

Cheers,

Stu.

Hi Stu,

No disappointment and absolutely no hard feelings.

Unfortunately, right now I can not give you much information because I do not have anything other than a battery with me.

I am a mechanical engineer, still working and interested in learning new things. As soon as I get some spare time, may be within a week, first I will go for shopping for suitable LEDs. Yesterday, one of my friends, an electronics engineer has agreed to help in designing suitable circuit to match the LEDs and my battery.

I will try to understand the circuit and will work on it improve it. My intention is to get best possible illumination with the locally and readily available LEDs at low cost. If I find it economical, I will use LEDs for lighting at home with AC supply or may be solar panels. On surfing the net I found the ones available are quite expensive compared to the price of incandescent lights and CFLs for the same illumination. I guess the manufacturing cost is actually not very high, but the profit is.

So, right now I am only at initial stage, it will take me some time, but I will certainly get back to you all if I encounter any problems.

Thanks Ess,

I know about 'the fun of the chase', but sometimes it's just better time management and economic sense to just go and buy the stuff.

We have it readily available here, which makes it easy. Right down to the MR61 converters for the dichroic DC halogens. Electronics stores carry the components, including the LED's

You still didn't tell where you are.

Cheers,

Stu.

If you can borrow a simple variable voltage power supply and you have a meter for current measurement you should be able to string your LEDS together however you like and feed them power note your readings and there you are.

garth CR4

Hi Randall,

Bullseye!! Your reply is excellent and precisely what I wanted. I have given you a GAR. I wish I could give you a higher rating.

I could easily understand your explanation. The info on German Company will also be helpful to start with. I will procure LEDs from them soon. Thanks a lot.