Introduction: USB or AC Powered Flashlight

Picture of USB or AC Powered Flashlight

Change this battery powered flashlight to USB powered or AC powered by using the AC charger with a USB port for any 5V device.

Step 1: These Are the Things You Will Need.

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27 LED flashlight from discount tool store
USB cable
3 feet (approximately) of red and black wires
5 ohm resistor or equivalent
heat shrink tube or electrical tape
small phillips screwdriver
round file
wire strippers
soldering iron
solder
RTV

Step 2:

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Test the light by pressing its switch several times.  If it is working proceed by removing 3 screws from the back of the light.

Step 3:

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Remove the batteries and four screws in order to remove the front cover.

Step 4:

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Remove the 2 screws that secure the LED board.

Step 5:

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Cut the USB cable to give you enough wire to easily work with.
Strip off the casing.
Peel back the shielding to expose the four wires of the USB cable.
Remove the shielding and cut off the green and white wires.

Step 6:

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Put small pieces of shrink tube on the wires.
Solder the red and black wires to their corresponding color of the USB cable.
Heat the shrink tube over the bare wires or cover exposed wires with electrical tape.
Put a longer piece of shrink tube over both wires and the USB cable and shrink to fit or cover with electrical tape.

Step 7:

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I did not have a 5 ohm resistor so I soldered two 10 ohm resistors in parallel.

Step 8:

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Insert a small piece of shrink tube onto the black wire.
Solder the black wire to one side of the resistors.
Cover the connection with the heat shrink tube or electrical tape.

Step 9:

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Remove a piece of black wire from the discarded USB cable.  Make sure it's longer than the green wire on the negative side of the LED board.
To find the negative side of the LED board turn the assembly over.  Look at the battery holder and find the side that shows to install the negative side of the batteries.  This is represented by a minus sign.  Turn the board back over.
Unsolder the green wire from the board.
Solder the black wire to the board where the green wire was attached.

Step 10:

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Make an opening for the wires in the empty end of the housing by using the round file.

Step 11:

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Insert a long piece of shrink tube onto the black wire.
Solder the black wire to the other side of the resistors.
Cover any exposed wire or resistor leads with the heat shrink tube or electrical tape.

Step 12:

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Remove the remaining green wire from the positive side of the LED board.
Attach the red wire to where the green wire was removed.
Now is a good time to see if the light works.
Plug in the USB connector to a powered on computer.
Press the on/off switch several times to test both sets of lights on the device
If the light does not come on it is possible you may have connected the wires to the wrong spots on the LED board.

Step 13:

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Tuck the excess wire and resistors into the empty end of the housing.
Be careful to avoid the screw holes and accidental damage to the wires.
Then secure the LED board to the housing with two screws.

Step 14:

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Reassemble all the pieces of the light.
Squeeze a small amount of RTV into the hole around the wires.  Allow to dry for several hours.

Step 15: You Did It!

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Test your light by inserting the USB connector into the USB port of a powered on computer.
Press the on/off switch to test both sets of lights on the device.
If you have an AC adapter with a USB port for charging a 5 volt device you can also use this to power your light.
Congratulate yourself.

Comments

joshabgvghn (author)2015-01-05

Runs on AC n batteries, batteries yes AC. Nonononono unless you're looking to set fires.

beljar4 (author)joshabgvghn2015-02-28

After it is modified, you plug in the usb connector to a 5 volt phone charger that is plugged into an ac outlet.

cosimaradu (author)2014-03-03

Quick question: Why do you need to add the resistor?

beljar4 (author)cosimaradu2014-03-03

The flashlight is meant to run on 3 AAA batteries. Since each battery is 1.5 volts the total is 4.5 volts. You need the resistor to drop 0.5 volts or else the whole 5 volts from the USB would power the light. I know from experience this is too much. It may work for a few minutes without a problem but it WILL melt the plastic and burn up the componemts inside the light.
I hope this answered your question appropriately.
Thanks for asking, it was a good question.

dray

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