Author Topic: cheap LED light disassembly  (Read 3534 times)

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dnix71

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cheap LED light disassembly
« on: March 10, 2013, 02:49:45 PM »
The $1US or so palm sized LED lights made in China and sold under no name have a reputation here for failing base switches.

I have quite a few and it took me a while to discover why the "switch" was failing. Disassembly isn't straight forward. The lens is the last piece put in place and it snaps in. With a curved pick and some effort the led circuit disk can be pushed back enough to get behind the lens and flex it out. The led circuit disk can then be pushed out from the inside. There is a spring under the disk which comes out last.

That large spring is the ground return through the body of the light. The center spring is positive into the disk and it is secured by a split contact that is tanged after the spring is set in it's slot. If either the center positive contact works loose or the spring fails to solidly contact three solder points on the disk, the light will fail. If you can disassemble the light, adding solder to those 4 spots is usually a permanent fix.





The three solder blobs at the edge of the back of the LED cluster is what returns current through the spring and then the body of the light.

richhagen

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Re: cheap LED light disassembly
« Reply #1 on: March 10, 2013, 07:00:56 PM »
I needed a small portable black light for a project and wound up taking one of those apart and soldering in UV leds. It worked out pretty well.  Rich
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RandomJoe

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Re: cheap LED light disassembly
« Reply #2 on: March 10, 2013, 08:29:29 PM »
Interesting, mine appear to have identical parts, but the head is made differently.  Instead of everything going in the front of the body, the head unscrews just like the back end.  The lens drops into the head first, the LED board next, then a ground-return ring screws in and tightens everything against the front of the head.  The big spring goes in last, compressed between the screw-in ring and the body of the flashlight.

Turns out that ground-return ring is what was giving my lights grief, not the switches.  Found that when I was messing with the LiFePO4 batteries yesterday.  On mine that ground-return ring had loosened and was making intermittent contact with the LED board.  My switches "failed" because I was pushing too hard (and frequently) trying to "get them to work"!  ::)  Once I tightened that ring, put the switches back together in the tail end, and tried them again - still work fine every time.  Of course I have to be careful - just a bit too much pressure and the switch pops out of the housing and I have to put it back together.

My flashlights are store-branded, bought at Office Depot.  Couldn't find them on their website, they are (were) just in a big bin by the registers.  They were a bit more than $1 though, maybe $3?

dnix71

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Re: cheap LED light disassembly
« Reply #3 on: March 10, 2013, 09:26:03 PM »
richhagen The price varies a lot here. At local auto part stores they were $1.99, elsewhere the price was higher, but at Walgreens one day I found a 4 pack for $5.

http://www.ebay.com/itm/140914429268?hlp=false&var=

This is very close to what I see locally. Note the retail delivered price for a single piece from China is $2US.

http://compare.ebay.com/like/380586135787?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

50 for $46US including shipping.

RandomJoe

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Re: cheap LED light disassembly
« Reply #4 on: March 10, 2013, 09:49:55 PM »
Now that's a lot of flashlights!  :P

Here are a couple images of the style I have:





Showing the 18500 LiFePO4 I'm using instead of the 3-AAA holder.  The black tape around the cell centers it nicely and keeps it from rattling.

richhagen

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Re: cheap LED light disassembly
« Reply #5 on: March 11, 2013, 12:48:00 AM »
I gave some of those away on past trips to folks who could use them, although at the time I bound a lot that had .5 watt led's and ran on one double A with some type of a booster circuit.  Once I found those I bought them because I thought they would be easier to keep operating where humidity and lack of batteries would take their toll.  I retrofitted them with the energizer lithium batteries for the trip to give them a bit more life before battery replacement.  I like the idea of the lithium iron phosphate batteries though because I figure I could pretty easily rig a charger for one off of the 12V available from the small batteries with the solar lights, and at $46 for 50 the lights themselves would be less than the batteries and if I grease up the inner threads and spring contacts well they could likely be kept running for quite a while even under those conditions.  Rich
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