What to make, suggestions please

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Cliffdenyer
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What to make, suggestions please

I have an old 950mah battery (From old blue cig chargein case) it’s usb rechargeable, was thinking of using it to power some kind of light. It’s 3.7 volts nom but it only outputs 0.2 amps is there any kind of led I can power with this? what can I make?

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Edited by: Cliffdenyer on 10/01/2018 - 17:16
DavidEF
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Well, you could power just about any “normal” 3volt LED from it. But, as you know, it will not put out very much light. Perhaps a nightlight or camping light?

You could make a flashlight still. Just don’t expect too much from it. Do you have any LEDs or would you need to buy them? For an idea how much you could get, I have some old XP-E2 R3 emitters. According to CREE PCT they will put out just under 90lm at 0.2 amp current. But, a XPL HI V3 at 0.2 amps will give you over 100lm and a XP-G3 S6 can make it over 120lm at the same current. Any of those would be a useful amount of light for anything close up, or for a night light or tent light.

If you do decide to build something from scratch, I think it’s not too late to join the contest. Wink

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Cliffdenyer
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I think it’s the perfect size to go in an altoids tin, with an emitter and switch, current is already regulated so just fix the star directly on the tin as heat sunk. Then find some kind of lens to cover it……

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DavidEF
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Yeah, that would be interesting to see. I think with such low output, not much heatsink is needed, so fixing it directly to the tin should be fine. But, how will you protect the LED from physical damage? You could use a TIR optic and just have to find a way to mount it.

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Cliffdenyer
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Time to get to in my local shop and find an altoids tin…..

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Cliffdenyer
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Hmmm the power supply won’t come on and light an led when connected to the star, but the multi meter reads 3.7v tried with two different LEDs…..

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Cliffdenyer
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Ah, the power out circuit won’t switch on if resistance is less than 1 ohm, maybe a switch will add enough resistance….

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Cliffdenyer wrote:
Ah, the power out circuit won’t switch on if resistance is less than 1 ohm, maybe a switch will add enough resistance….

Or a “sense” resistor.

Look here: LED calculator for single LED circuits and here: LED series/parallel array wizard for multiple LED emitter arrays.

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Cliffdenyer
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Thanks David, super helpful so now I’m after a 1 ohm 1/8 watt resistor….

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https://drive.google.com/folderview?id=0B8pVbTjh0vt8Sy1WV3pjUlB2YVk

Battery and charge board mounted in an old Gameboy game case, switch and led attached with reflector.

Next job will be to mount it in a small tin of some kind, estimated lumens 50-80 ish compared to low mode on some of my other lights.

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What is the max current rating on that LED? Is it enough to handle the 0.2A output of the battery?

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Since you’re making this light from scratch, would you like to enter the 6th Annual Old Lumens Scratch Build Contest? There’s no reason not to, and you might win a prize. You’d just need to tell _ the_ that you are entering and start a separate build thread for it.

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I’m not sure it will be worthy of that….

The led is still attached to its original board with a resistor attached so current shouldn’t be an issue,

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Now have a small tobbaco tin to mount everything in,

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