Hacked Gadgets Forum

March 6, 2007

Make a USB Charging Flashlight

at 5:26 am. Filed under DIY Hacks, Electronic Hacks

After reviewing the Forever Flashlight for The Gadget Panel I couldn’t help but take its capabilities to the next level. I wanted a portable USB charger that could recharge things like my iPod Shuffle. I know there are lots of battery powered options, but I wanted something that didn’t need battery replacement. USB power is 5 Volts and that is exactly what this flashlight puts out on the auxiliary power plug so there is no voltage level conversion required. I also like the fact that this flashlight has Ni-MH batteries inside, not just some big capacitors like some other units.

The parts and tools you need are:

* Flashlight
* Female USB connector
* Small barrel connector
* Heat shrink (optional, could use electrical tape)
* Lighter or heat gun (if heat shrink is used)
* Solder
* Soldering iron
* Wire strippers
* Multi-meter

You can use any female USB connector, I bought a USB extension cable which obviously has a male end and a female end. You could also harvest the USB connector from an old motherboard.

I had a barrel connector that was the correct size, it came from an old plug in power supply that was used for something else. The barrel connector should be available at stores like Radio Shack.

There are a few different styles of connectors, this one has an exposed metal area. I would have preferred one that was completely covered in plastic but this is what the store had…

Strip the ends of the barrel connector with the wire strippers. If you have bought a barrel connector you can simple skip this step.

Chop of the length of USB cable desired and strip off the outer insulation. Be careful not to damage the wires inside since the wires are very delicate.

Cut the braided wire and remove the white and green wire. The wire and green wires are used for USB data which we will not be using. When cutting the white and green wires make sure that they will not short together or to the braided wires. The Red and black wires are used for the USB power, use the wire strippers to strip some of their insulation.

Now plug in the power adapter into the flashlight (the adapter is included with the flashlight). Insert the barrel connector into the power adapter ensuring that the wires do not short out. Use the meter to check the polarity of the wires. As you can see the meter is indicating 5 Volts. The red lead is connected to positive and the black lead is connected to negative. Mark the positive in some way so that it can be easily identified.

Slip some small heat shrink over the barrel connector leads and a large piece of heat shrink over the USB wire. I wanted the large heat shrink to be black but I ran out of that color…

Twist the wire from the barrel connector that was determined to be positive to the red USB wire and solder them together.

Next solder the negative wires together, make sure the wires are the same length when soldering to ensure they will have the same amount of strain on them.

Slide the heat shrink over the wires and heat with a heat gun or a lighter.

Don’t over heat the heat shrink since it can melt the solder inside and cause a bad connection or even a cold solder joint.

Slide the large heat shrink over the entire splice and heat that into place.

Plug in any USB device and check it out! I plan to keep this unit in my car, now if my cell phone dies or my iPod needs a quick charge I will be prepared.