This project came about because I have a decent amount of LED projects around my house and my friend asked me if I could turn one of those into a light he could put behind his TV! But he has his TV hung on the wall and didn't want to have any wires hanging down or anything that required being plugged in. I took a look at his TV, and it, along with most new flat panels, have a couple USB sockets on the side. And I thought PERFECT I can just use the 5 volt power out of the USB port!
This is a really simple project that looks great! You can use the idea of this project for many different ideas and areas-- not just for behind the TV!
Step 1: Parts and Tools Needed
USB cable (cannibalize it off of any old or broken electronics)
Container (any container that you like, choose one that fits your project!)
Resistors (correct resistance for a 5-volt power supply and your LED's. If you are not sure check out the LED calculator)
LED's (any color you desire)
Spray Paint (whatever color or texture you want!)
Hot Glue Gun
Step 2: Preparing and Painting
Take your container, spray paint and some paper/cardboard outside to get ready to paint. You can paint the inside of the container if you like but there is not really a point so just focus on the exterior of the container. Lay out the container and the lid a foot or so apart so you can paint each piece individually. I suggest painting two or more coats to make sure you have the container well covered.
Once the paint is dry we need to drill some holes for the LED's. I used 3mm LED's so I grabbed a 3mm drill bit. If you are using 5mm LED's, or bigger then grab the appropriate drill bit for those sizes. To get the LED's spaced out nicely on this curved surface can be a bit tricky.
Here are two ideas to help you out
1) Grab a piece of paper (or blue painters tape) and wrap it around the container and mark where the paper overlaps. Lay the paper down flat and you can measure out how to space apart the LEDs and mark them on the paper.
2) Take that paper and fold it in half, then half again, and again. Then you can use the crease marks as the evenly spaced points to mark)
Once the paper has the marks where you want the LED's on it, take the paper and wrap it back around the container and tape it in place. Grab your drill and the drill bit that matches the size of you LED's. Then drill in to each mark. Use very little pressure and go slow to keep the holes nice and clean.
Now we need to drill one more hole for the USB cord to enter the container. You can drill that hole wherever you want the wire to exit the container. When you have finished, give yourself a high-five because you are all ready to start the electronics part!
Step 3: Wiring Up the Electronics
The parts I used are 10 3mm Blue LED's, and for each LED to run off of 5 volts I used a 100 Ohm resistor for each LED. So using 10 LED's and 10 Resistors, you are looking at a 200mA draw from the USB Source. From what I have read, a USB source has about a 500mA capacity, so we are well in our limit!
Here is a little technique that I have come up with in previous projects; take your LED and cut the Negative lead so it is about 1/2 inch long, and take your resistor and do the same to one of the leads (see picture below for example). Now solder the short negative lead of the LED and the lead you cut on the resistor together. Do not take too long to solder so close to the LED because you can overheat the LED and burn it out!
Now you have a LED with a resistor attached! With this you are unstoppable--you can take over the world (or not)!
Repeat for all your LED's (in my case ten of them).
Next grab the LED's and bend the resistors up into a 45-90 degree angle (as seen in the pictures). Put all the LED's into the holes drilled out in the container, so that they are placed into their final positions with the negative/resistor leads pointing up. When the LED's are placed this way, the positive leads of the LED's should be all pointing towards the center. Solder all the positive leads together. If they can't reach each other then use some wire to connect them. I used some of the scraps from the cut-off leads we did earlier!
Once all of those are soldered together, the LED's should feel a bit more sturdy! For the negative leads/resistors, I bent them up into a nice dome to get the ends to reach each other (see pictures for example). The reason for creating this dome is one; looks. Two; you need to make sure the negative and positive leads do not touch! Also I thought it would be kind of nice if the circuit looked interesting, too! In my case I was using a metal container, so I had to make sure the leads were not touching the container.
Now that you have all the Positive leads together and all the Negative/Resistors soldered together, all you need to do is add some power to light them up!
Grab you USB cable and strip back the plastic coating about a inch. There should be multiple wires exposed. You can cut off all but the red and black wires (the red is positive and the black is negative). If your USB cable looks different inside, check which wires are positive and negative before soldering anything.
Strip back the plastic from the red and black wires about 1/4 inch exposing the metal underneath. Slide the wire into the hole in the container that you drilled out earlier. Solder the negative to the negative and the positive to the positive. Grab your hot glue gun and glue the wire in place from the inside of the container.
Step 4: Finish and ENJOY!
I hope you had fun building this project! I have attached a handful of pictures of the TV backlight in action. If you want to see anymore picture, let me know! Also, I am open to any questions or suggestions that you have.
Thank you and enjoy what you have created!