Make a simple USB light

The parts list is simple and I had the materials lying around. You can probably get this from a Radio Shack for a few dollars or scavenge something broken.

Parts
-62ish OHM resistor***
-LED of your choice
-Old USB plug
-Twisted wire or hookup cable
-Relatively stiff wire (doesn't have to conduct electricity)
-Sugru (optional)
-Some tape (electrical is probably the best)

***Resistor may vary depending on your LED needs. Source voltage is about 5 volts from USB. I suggest this website if you don't want to second guess yourself: http://led.linear1.org/1led.wiz. I use it all the time because I doubt my math abilities.


Tools
-Wire snips
-Soldering tools
-Scissors/hobby knife




First you will want to decide how long you want the light to be. I guesstimated and cut mine about 15 inches. You will want to cut two of these for positive and negative. Second you will want to cut up your USB plug as it show in the picture.

Pro Tip: Don't use a USB plug with shielding like I had. It makes it far more annoying to cut up with shielding.

After you hack up the USB plug, find the positive and negative wires. Don't assume that red is positive and black is negative. Never assume in electronics. In my case, yes red was + and black was - :). But I checked and that's what counts. Cut the other wires if any, you just need power.

Strip your main wires and solder them closely to the LED on the LED pins. Remember which pins are positive and negative. If you forget, you can look inside the diode and tell. The to pins connect to a large metal piece and a small metal piece in the diode. The larger of the two inner metal pieces is the negative side, the smaller is positive. Found this out by forgetting which one was which after I cut them.

Once you have the positive and negative wires separated out on the USB plug, it's time to start soldering. Solder the resistor to one of the wires. You want to solder it as close to the base as possible just to keep everything compact. Once the resistor is soldered on, solder the LED wires to the USB plugs wires and remember to get the polarity right.

After it's all soldered up, plug it in and make sure it works. This is important in case something was messed up. You don't want to finish the project just to find out a wire was wrong or a solder joint was bad. After you confirm it's working, seal the joints with tape or some liquid tape. Cram the wires on the USB side back in to the sheath as much as you can and then tape it back up.

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This can be done many ways and has many options. Below are a few things I may try if I ever do a version 2. I found out too this is a pretty good laptop light for typing at night. However, it's a little long for that so if you want it for just a computer light, I would suggest just a few inches.

-Use a potentiometer (like a 0-200 ohm pot in series with a 62ish ohm resistor) for variable light.
-An on off switch
-Use magnet wire so you don't have to have the conducting wire and support wire separate.
-Have the LED swappable so you can change colors.

Posted in: Electronics, LED