USB Rechargeable Li-Ion LED Flashlight



Introduction: USB Rechargeable Li-Ion LED Flashlight

Greetings fellow Makers,

The inspiration for this little project came to me when my cheap Chinese MP3 Player died on me.
After a failed to bring it back toy life, I found out that the battery and charging circuit
where intact and in good working order.
So I now had the basic "module" for this flashlight at hand!!  :-)

THE PARTS LIST... and descriptions:

Even if you do not a broken one, this really is the easiest and cheapest way I could find
to get your hands on a small Li-Ion battery, complete with a charging circuit and a miniUSB connector.
Just do a search on eBay for "SD MP3 PLAYER CLIP" and get the cheapest one you can find.
TIP: Try to get the one with the little screws on the side. It should be easier to open up.
I had to Dremel me way inside mine.

This is going to be the project enclosure. We need something cheap and nice looking.
I had those 4xAA battery boxes laying around that are a perfect match for this build.
Go on to eBay and search for "AA BATTERY PLASTIC BOX".
CURRENT PRICE = $0.99 for a set of two (2) boxes.

Fairly generic item. Just to go for the brightest ones you can get (over 17000mcd).
I used four (4), but you could use 3 or 5 even. "Battery life VS brightness" should be considered here.
I found that 4 LEDs give a nice compromise between them.
As with everything in this build, I had some laying around,
but on eBay 10 pcs 20000mcd 5mm LEDs have a CURRENT PRICE = $1.38

Here you can use whatever switch fits in the box.
But given the size there aren't many options out there.
Micro-Switches can be salvaged from a lot of machines (ex. large printers),
but are quite cheap to buy also. On eBay they have a CURRENT PRICE = $1.84, lot of three (3).

That it as far as materials go...

Now you have your basic TOOL LIST:
Small side cutters, small flat file, soldering iron with fine tip, digital multimeter,
needle-nose pliers, small Phillips screwdriver, and a Dremel maybe...

And in case you haven't already figured it out... here is the INSTRUCTIONS:

1. Open up the MP3 Player an remove the PCB along with the battery.
2. Remove any protrusions from inside the plastic battery case using a side cutter.
3. Test fit the PCB inside the box as per the photos.
    Some filing will be necessary in order to fit. You can use a Dremel for this.
    In any case be very careful not to damage any coper traces on the PCB.
4. Make small holes for the LED legs to pass through.
    Use a very small hand-drill. You can use your soldering-iron tip also, but keep them small.
    Also cut out holes for the miniUSB and the micro-switch with the side-cutter.
    Use the file to make the edges nice and smooth.
5. Put in the LEDs and glue them in place with super-glue (GEL type glue is preferred).
6. Solder the LEDs in parallel. OBSERVE POLARITY HERE!!!
7. Connect the Negative lead of the paralleled LEDs to a ground point on the PCB.
    The metal casing of the small switch worked for me, but you could find other points also.
8. Connect the Positive lead from the paralleled LEDs to one of the contacts on your mSwitch.
    And then the other contact to the PCB, where the little red cable from the battery is soldered.
    (In essence, you are wiring your LEDs, through a switch all in parallel with the battery)
9.  Glue the switch and the PCB down with super-glue. But don't glue the lid shut!

And here you got.
You just made a small USB rechargeable LED flashlight!

Now you can close up the lid of the box.
You can find a rubber band that muches the box color and use it as permanent-on switch
(by holding down the Micro-Switch). Beauty!

And even if you had none of the parts laying around,
the total cost of materials is $4.80

Hope you liked it.
Leave you comments at will!  :-)

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