Small Eiger LED Torch

[Widget]

Hopefully this falls under "weird devices".

I have a small torch, nothing special. I tried using it today, but it turned off after a few seconds. This happened a few times. Then the LED inside started to get dim and flicker, then it would go off, then it would come on bright, then off, then on dim and flicker etc... if you get my drift. The battery is a AA 1.5v which works fine.

Now, it won't come on, so thought I'd tear it down and have a tinker. I'm still a novice, so don't really know what I'm doing. I thought I'd try the LED to see if it works (which lead me here).

I desoldered the LED and supplied battery power, but it doesn't light up. When I use Diode mode on the Multimetre, it lights up very little. So this part confuses me. Why does it light up (a little) with the MM but not a battery?

Surprisingly this torch has a tiny circuit board, which I didn't take any components off due to the size.

Bunnings don't sell them anymore but I found an ebay listing saying it's a 1W LED @ 60 Lumens.

Here's my Flickr album with pictures of the LED+circuit board.

https://www.flickr.com/gp/198784515@N03/D56jM1vY0V

Sorry for the odd post. Hope someone can point me in the right direction.

[EDIT] Do these types of LEDs have a specific name? I found some on ebay 20 Pieces 1W LED High Power SMD LED 28mil Light Bead SUPER COOL WHITE LED Diodes though not 100% sure if they're correct as it says normal voltage is 3v.

Regards,

[stj]

Re: Small Eiger LED Torch

the circuit is a boost convertor - it's driving the led with 3 to 4v

[Widget]

Re: Small Eiger LED Torch

Couldn't EDIT original thread so editing as a reply

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[EDIT] Ok, a bit of reading and found (the) LED needed higher voltage (3v) to function. I supplied it with 3V and it light up OK. So looks like the issue is with the little circuit board not the LED.

[Widget]

Re: Small Eiger LED Torch

the circuit is a boost convertor - it's driving the led with 3 to 4v

ha! thanks stj. Just tried to edit the original post with the updated info. Thanks for getting back to me

Looks like I'll have to tinker with the circuit board now. Will I need to remove all components to properly test? I tried checking the resistor, it started at a figure then dropped down to 0.01, so not sure if there's interference.

Thanks again

[eccerr0r]

Re: Small Eiger LED Torch

I have a boost converter 1-AA LED flashlight, if the battery is not quite up to snuff it does some weird flickering as if there's some connectivity issue but rather it just needed a new battery.

[CapLeaker]

Re: Small Eiger LED Torch

It has also something to do with the internal resistance of a battery. Same 1AA flashlight on a single NIMH battery, shines brighter than when using some alkaline battery.

[petehall347]

Re: Small Eiger LED Torch

switches and battery contacts should be checked first

[stj]

Re: Small Eiger LED Torch

some clicky switches are crap and need to be sprayed inside with contact cleaner.
easy to test by just bypassing it

[eccerr0r]

Re: Small Eiger LED Torch

Yes due to the internal resistance of alkaline/carbon zinc batteries* and the fact that these converters have hysteresis on acceptable voltages, this can lead to weird flickering when using a high internal resistance battery.
Note that with a 1.5V battery trying to power a 3V LED, you need to draw 2x the amount of current in a ideal world. My 1-AA flashlight uses a 1W LED, and at 1.5V would need to draw almost 1 amp of current due to conservation of energy and component losses. At 1 amp, any resistance in wires or internal to battery will cause significant voltage drop, and these voltage drops will mean less voltage to the power supply, causing it to shut down.

Yes a 600mAh NiCd AA battery only lasts like 30 minutes in my 1-AA flashlight!

* carbon zinc batteries are frequently not recommended in these boost circuits because their internal resistance is so high, causing short battery life (measured in single digit minutes likely) and significant heating of these batteries.

[Widget]

Re: Small Eiger LED Torch

I have a boost converter 1-AA LED flashlight, if the battery is not quite up to snuff it does some weird flickering as if there's some connectivity issue but rather it just needed a new battery.

It has also something to do with the internal resistance of a battery. Same 1AA flashlight on a single NIMH battery, shines brighter than when using some alkaline battery.

switches and battery contacts should be checked first

some clicky switches are crap and need to be sprayed inside with contact cleaner.
easy to test by just bypassing it

Thanks Guys. i tried a new battery ('Activ Energy' from ALDI) but still did the same thing. Interesting information on the batteries though. Are there any recommendations on a particular brand or type (NiMH or other) you would recommend over Alkaline?

The clicker on the back I tested first with continuity. Seemed to test good, though as the LED itself seems ok, I'll resemble and bypass the clicker just to confirm.

Yes due to the internal resistance of alkaline/carbon zinc batteries* and the fact that these converters have hysteresis on acceptable voltages, this can lead to weird flickering when using a high internal resistance battery.
Note that with a 1.5V battery trying to power a 3V LED, you need to draw 2x the amount of current in a ideal world. My 1-AA flashlight uses a 1W LED, and at 1.5V would need to draw almost 1 amp of current due to conservation of energy and component losses. At 1 amp, any resistance in wires or internal to battery will cause significant voltage drop, and these voltage drops will mean less voltage to the power supply, causing it to shut down.

Yes a 600mAh NiCd AA battery only lasts like 30 minutes in my 1-AA flashlight!

* carbon zinc batteries are frequently not recommended in these boost circuits because their internal resistance is so high, causing short battery life (measured in single digit minutes likely) and significant heating of these batteries.

Hmmm, thanks eccerr0r. But with a new good 1.5v battery, it should still work though, even for a limited time, right? I might put back together and probe the PCB for voltage (should have done that first I suppose).

Thanks again

[eccerr0r]

Re: Small Eiger LED Torch

It may work for a few minutes (like 5 minutes) if brand new before it won't work anymore, at least for carbon zinc. Alkaline batteries should last longer, probably on the order of a half hour to hour or so, but the rechargeable cells have much longer lifetime compared to alkaline batteries of the same capacity. Measure the voltage of the battery while the lamp is on and ensure it stays above a volt or so.

Again since it was designed for single cell use, these flashlights are a huge drain on the battery. It's the tradeoff from needing to use 3 cells which is the easy way out trying to light a flashlight with off the shelf batteries.

I'm using a NiMH cell in my 1-AA LED flashlight now, it has acceptable battery life.

[stj]

Re: Small Eiger LED Torch

your problem could be the led going open-circuit as it warms up,
or the clicky switch - try linking the lamp body and battery with a bit of metal instead of fitting the endcap with switch.

as for batteries, the best are made by Eneloop (Panasonic) but they are expensive.
luckily you can get them cheaper because IKEA sells them re-branded as LADDA.
buy the 2400mAh ones - they are high current

https://www.ikea.com/au/en/p/ladda-r...1-2v-50504692/

[Widget]

Re: Small Eiger LED Torch

Thanks for the feedback guys,

I had the LED + circuit setup outside of the torch body and things seem to go well. I re-installed into the body and it started playing up.
I took it apart again and had a closer look, I noticed on the battery housing, the metal tube connecting the ground to the circle circuit, didn't have as much contact on one side but more on the other (see pictures in link)

https://www.flickr.com/gp/198784515@N03/R12BwBD3ty

I rotated the barrel so the tube that protrudes more sits against the ground on the circuit board, if you know what I mean.

So far, light seems to be ok, at least it stays on longer than before, so perhaps a lack of ground contact or or something happening with the contact after a certain period was causing the issue?

[stj]

Re: Small Eiger LED Torch

i like to clean the threads and contact area's on aluminium lights and then grease them - stops oxide forming

[Widget]

Re: Small Eiger LED Torch

i like to clean the threads and contact area's on aluminium lights and then grease them - stops oxide forming

What type of grease would you use?

[stj]

Re: Small Eiger LED Torch

silicon grease.
you can get it from plumbing places for use on rubber seals

[Widget]

Re: Small Eiger LED Torch

silicon grease.
you can get it from plumbing places for use on rubber seals

Thanks stj, I'll give it a shot