Introduction: Hack Ikea Ljusa Crank LED Flashlight Into an Emergency USB Charger

This is my first instructable. Note: I WILL NOT BE RESPONSIBLE FOR ANY DAMAGE!

If you live anywhere there is a risk of losing household power and you don't have alternative sources of electricity, you might find this useful.

What you need:

- Ikea Ljusa Crank LED Flashlight ($6+tax)
- USB extension cable
- A drill and drill bit with the same diameter as the USB extension cable
- Soldering iron/gun and solder of course
- Voltmeter or multitester (useful for checking)
- Philips screwdriver
- Knife or precision screwdriver (for prying open)

Step 1: 1. Start Prying

Using a knife or flat precision screwdriver, carefully lift off the front cover. Sorry for the blurred image.

After I pried the cover off, I found out it is screwed on. I assume it was also glued because I could not unscrew it.

Step 2: 2. Remove the Cover

The cover, lens, and LED bulb housing should come off. There will be a black (negative) and a white wire connected to the LED bulb housing. The white is connected to the switch. 

Remove the three screws to release the switch. 

Step 3: 3. Solder the Wires

I wasn't able to take pictures of the cable because I was reusing an old one, but it shouldn't be hard to figure out these steps.

Cut the female USB extension cable about 4" from the female end. Strip off about 2" from the outer insulation, then strip off about 1/8" off the insulation of the black and red wires for soldering. By common convention, power is coursed through wires of these colors.  Cut off the other wires.

Take the remaining male end of the cable and expose the red and black wires. You will find this useful later for testing.

Note: Your USB cable may have different colors, so you will need a voltmeter/multitester to find out which wires have power, and which ones have the correct polarity. Just plug the male end into any USB port and with the multitester find out which pair of wires register 5V.

Drill a hole on the side of the flashlight about 2" from the front of the flashlight, on the side opposite the switch. Remember this is plastic, so do sowith care. Push in the USB cable into the hole and pull out the exposed ends.

Solder the RED (positive) wire to the WHITE wire where it connects to the switch FROM the capacitor found farther inside the flashlight (NOT where the white wire connects to the LED bulbs). Do this quickly so you don't unsolder the white wire from the switch terminal. 

Solder the black (negative) wire from the USB cable to where the black wire in the flashlight connects to the LED bulbs. As with the other wire, do this quickly and carefully.

Step 4: 4. Replace the Cover

Replace the switch using the three screws. Make sure you line up the switch with the silicone cover, and that the wires don't get in the way.

Test the flashlight by giving it a few cranks, then pressing the switch. Turn off the flashlight, then test whether it is actually producing electricity through the USB port by plugging in the cut male side of the USB extension cable and using a voltmeter/multitester to measure the power at the exposed ends. You can of course also test it by plugging in a device and see whether it is charging.

After testing, screw back the cover. The only thing to note is that there are notches on the LED bulb housing that should line up with the slots on the flashlight body.

Step 5: 5. Secure the USB Port

Secure the USB outlet to the side with a glue gun. As you can see from the sloppy result, mine needs replacing.

Note where the hole should be drilled.

I considered installing the USB port inside the flashlight to get a cleaner look, but there isn't enough space.

Step 6: 6. Test It

As the images show the phone is charging. Note that this charger should be used only for devices whose batteries are drained. Otherwise the device might charge the flashlight, with unforeseen consequences!

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