How to Light a LED or Regular Light With USB!!




This Instructable is going to teach you how to light a light bulb through a USB!!

SORRY: I currently have no camera so I can not load up any pictures!

BUT: I do have a scanner so I will do the best I can.

I guess you could use this when its dark and you don't have a light source or you want to save money. :P

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You will need:

1) USB Cable. (Male Type A)
2)LED, regular light (what I used)
3) Electric Tape (I didn't have any so I used regular clear tape and burned it to mold it)
4)A Computer (duh... to power the light)
6)Wire Strippers

Step 2: USB Preparation

1) Cut USB cable to desired length.
2) Strip about 1 inch of the insulation.
3) There should be four wires, cut off the green and white wires.
4) Strip about 1/4 inch of the insulation of the red and black wires.

It Should Look Like This:

Step 3: Light Preperation

Do I really need to explain this?
If you really don't know, then make it so it looks like the picture below:

Step 4: Joining the Two

Just hook up the wires together. It doesn't really matter which way you do it.
if you have a soldering iron, than go ahead and use it.

Step 5: Plug It IN, Plug It IN!

Plug the USB into the Computer and wha-la!! It works!!

i'll try to upload a picture as soon as i can so you can see it actually works for all you non- believers.

Oh and, i found out that if the light is plugged in for about 10 minutes, it goes out. if anyone knows how to fix this problem, please contact me via email or comment. thank you.

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25 Discussions


10 months ago

Does it matter which wire goes where? I have led lighr bulb with two pins sticking out and they look exactly the same...


10 months ago on Step 5

I think that the l.e.d went out because you are using 5v for your l.e.d instead of 1.5 volts. You can get 5v l.e.d.s from eBay that have a built in resistor to limit the current.


7 years ago on Step 4

cool substitute for soldering irons, i have to try that !!! :))))


7 years ago on Introduction

nice idea of scanning the objects instead of taking pics.... ill try that sometime :)


Reply 10 years ago on Introduction

yup, i did. i had a conversation if you read the comments. but the resistor i used really dulled out the light


Reply 8 years ago on Introduction

You just used too big a resistor. Try a 100ohms, then if it's not blasting go to a 47ohms one, etc. (33>22>10>4.7ohms). LEDs aren't very forgiving of too much voltage!


10 years ago on Introduction

I tried something similar. Using an LED hooked up to the end of a USB. The LED light worked, but after a while started smoking and would have eventually burnt out, or worse.

I also tried it with an on/off switch and got an error from Mac OS X that it was disabling the USB port because it drew too much power...had to restart to get it back to normal. Thank god for safeguards eh? Needless to say thats the last time I will experiment with my pricey Mac USB ports until I know EXACTLY what I am doing.

A resistor was definitely needed in my case. Here is a site with instructions for various LED configurations and a resistance calculator that I found very helpful for an electronics noob.

The point is that impatience and experimentation without proper knowledge almost always leads to disaster. I was lucky.

4 replies

It's still a good idea to include a resistor. When you power an led from a battery, the battery's internal resistance acts as the limiting resistor. However, depending on the actual led, it may need less or more voltage. I usually stick in a small resistor no matter what (10ohms or so) just in case a new battery has a slightly higher voltage. The 1.5v battery probably won't even light a white led, torches which use only one battery have a step up circuit to raise the voltage to the volts needed by the led. Have a look at Joule thieves here for a simple circuit.


Reply 10 years ago on Introduction

It also helps to know what type of LED you are planning to use. Don't expect to just de-solder one from something else and hope for the best.


8 years ago on Introduction

Adding a resistor over 100ohms should be fine. This will give approximately 20mA drive current, which won't blow anything up. You could go down to 47ohms probably. As you go over 100ohms, the led will just get slightly dimmer, but anything between 100-330ohms should be fine, bright enough without any blown leds..


10 years ago on Step 5

The reason that it went out is that your usb port gives out 5v and most led's use around 3 volts. SInce your providing too much electricity to the LED is burned out and cant be used again. You'll need to connect a resistor to your circuit to lower the current from 5v to the voltage you need. And ide recomend using a LED Resistor Calculator to see what resistor you need based on the voltatge that your led requires.

2 replies

Reply 10 years ago on Step 3

no its not, its a regular light. but it works either way, led or regular light.