Halloween Costume
It's been a couple weeks since halloween, but this is worth writing up anyway. Last year I had been thinking about doing some sort of costume using LEDs. The prices on flexible RGB LED strips have gotten really cheap, so it seemed like a good time to try to build something with them. I hadn't come up with any good ideas for what to actually make until a few days before Halloween, when a friend showed me a video of an LED stick figure costume that had gotten a lot of attention last year. So, a few days before Halloween, I decided to try building my own. Thanks to the magic of Amazon, I got a 5 meter roll of LED strip shipped next day for $15. An old sweatshirt and pants were found to attach everything to.
Putting it together was fairly simple: lay out each section of strip and cut it to length, solder wires on, then stick it in place using the adhesive back on the strip. Each section was wired in parallel so they would all light up the same color. The power supply and controller are directly connected to the section on the pants, which the sweatshirt then connects into with a 4-pin header.
I only had a couple hours to throw the controller together and get everything working, so I stuck to using a Teensy 3.1 for simplicity. TIP120 transistors are used to control each of the red, green, and blue channels. The whole thing is powered from a 3S RC battery via a 5V voltage regulator. The LED strips can draw over an amp when all three colors are on full brightness, so the regulator really should have had a heat sink. As it turned out though, running the LEDs at a max of about 20% PWM duty cycle was more than bright enough at night. With the patterns I was using, power usage was only in the 100-200 mA range, so everything could run off of a tiny 1000 mAh battery for several hours.
Since the Teensy is programmed the same as an Arduino, getting the code working was easy. At first, I just made a simple pattern that fades in random colors. I later added a button to switch between modes and made a few more patterns. One of those was strobe mode, which flashed white at full brightness… it produced quite the effect outside in the dark!
It all ended up working well for something thrown together last minute. The adhesive on the LED strips held onto fabric better than expected, although not enough to be a permanent solution. After the first night running around with it, some of the strips were peeling off, so I spent much of the next day sewing everything on permanently. Very tedious (probably since I have no idea how to do it correctly), but made things much more durable.