Instructables
Picture of Make a simple USB light
I've recently acquired a "high end" soldering station so I find myself enjoying soldering lately. That being said, soldering always needs good lighting. I almost always have my computer next to me when I'm working on something so I decided to make a simple little USB light that was easy to manipulate and put where it needs to be.

Step 1: Parts needed

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

Step 2: Cutting

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.
 
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awesome project :)
snotty2 years ago
Nice project.

It's screaming to be done with shrinky tube instead of tape.
So I saw the part where it said "make the LED swappable" and so I said, Challenge accepted. All you need is an old strand of lights! clip one socket off and then stick some led's in the bulb housings and voila! Interchangeable lights! Thanks for the instructable!
Noahtoyou2 years ago
do you need the resistor?
CaptPikel (author)  Noahtoyou2 years ago
A resistor is needed for an LED for a USB supply. Some LED's come with the resistor built in. You would need to look at the LED specifications. With no resistor, most LED's would burn out almost instantly.
soshimo2 years ago
Just use Ohms law to figure out the resistor value. Find the voltage drop of your LED (it's on the spec sheet), usually 1.7 - 2.4v. Ohms law says I = V/R. You want about 20ma of current through the LED (more and you will shorten the life - a lot more and you will shorten it considerably and let out the magic smoke). So, given that .02 = V / R and we know that V will be supply minus the voltage drop across the LED, or V = Vcc - Vled. Let's use 2.0v as an example, so 5.0v - 2.0v = 3.0v dropped across the resistor. So now we know V, let's solve for R. R = V / .02 or 3.0 / .02, or 150 ohms. The next highest value that is standard is probably 220 ohms so go with that. Anything less and your LED will not last as long and/or you could fry it.
CaptPikel (author)  soshimo2 years ago
I know the math. I just don't like dividing decimals, digging for a calculator and making mistakes. I'd rather use a program. I have a program I wrote on my calculator but I have to find the calculator :). My laptop is always there and I've never lost it. Works for me.

I made sure to point out different diode ratings. I've blown a few in the past assuming they needed the same power.
I personally don't like those calculators. They tend to abstract what calculation is going on. Ohms law, KCR and KVR are all derived from Maxwell's equations. There is a reason why they work and understanding those ratios, at least at a higher level than Maxwell's stuff, is important when building circuits. Just my two cents. When I teach BEE I always stress learning Ohms law over using some calculator app. Will that app tell you how to bias a transistor for class A operation? Of course not, but Ohms law will! :)
CaptPikel (author)  soshimo2 years ago
I agree. Knowing the math is important and will help you in the long run especially in troubleshooting, but I'm lazy lol. I just go with what's easiest and quickest most of the time for simple things like this. I'll admit I'm more of practical electronics than the theory behind it, and I regret it most of the time by burning up things. If it's something complex I'll sit down and work it out, but for LED's, I just use a calculator. I know the rough range it should be in so it's not like I'll trust it if it throws some crazy result at me (I have seen a few do that).
Lolbert2 years ago
Here's an idea! How hard would it be to replace the earbuds on a pair of headphones with LEDs so that the electricity going through the audio jack would make them flash along with any music you're playing? Would the audio cable not supply enough power? Of course, you would have to have a headphone splitter if you actually wanted to listen to the music at the same time.... It's a highly impractical project, but it might be fun for experimentation.
marmand Lolbert2 years ago
Sharpshot, you could hook something like this up but in all likelihood it wouldn't be nearly that simple. To begin with, an analog audio signal like the kind coming out of an audio jack is AC, whereas an LED (by definition of being a diode) only allows current flow in one direction, and so would really only work (or would work most practically) with DC, so you'd need some rectification circuitry to accommodate that so it would accurately reproduce the sound as flickering light. Additionally, the voltage level of that signal is in all likelihood very small, in the millivolts (mV) range, whereas supply voltage and current for an LED would need to be much higher than the signal would provide, so you'd need some amplifier circuitry to step the signal up to the required level.

So yes, it would be possible, just not as simple as your initial thought. If you're interested in finding out more about it you can always play around with it yourself, or check out the link at the bottom, its a similar concept to what you're thinking.

http://www.radioshack.com/product/index.jsp?productId=11007963&CAWELAID=711102272
Led Man2 years ago
question. where do you buy Sugru at?
CaptPikel (author)  Led Man2 years ago
I got mine directly from their site. Other places sell it but from what I googled, it was cheapest directly from them. I ordered 12/3 and got it 12/8.

https://sugru.com/us/buy
you can also make your own. There are several Instructables that tell how to do it.