My friend Oscar asked me if I could help him with the electronics for his "Ghost Buster" Halloween costume this year. His vision was to recreate the original proton packs from the movie. The circuit would simply turn the four red lights on the back of the proton pack on and off in sequence. This would also include a power switch and a knob to control the rate of the blinking LEDs. I started by searching the web for LED circuits and the first thing I stumbled upon was great website which turned out to have a large resource of free circuit designs. I found an LED Chaser circuit that could control the LED sequence. The circuit combines two IC's (integrated circuits) a 555 timer chip and a 4017B CMOS decade counter. Most of the materials and parts you'll need to build the chip can be found either online or at your local electronics store(RadioShack, ect). To build a prototype on a breadboard you'll need a few resistors (1K, 10K), a 2 10uf capacitors, a 10K-500K potentiometer, 11 LEDs and lots of wire. Below is the circuit design for the LED chaser from www.elecfree.com.
We started off by building a prototype on a bread board. This step is easy just follow the diagram and make sure that all of your connections match the circuit above. Once we tested the chip on the bread board we were ready to design our PCB (printed circuit board). Oscar found a free multi-platform application online for designing and testing PCB's called EAGLE. The program is easy to use and comes with a library full of parts to use. You simply select the parts you need, lay them out and wire them together. Export the final board from EAGLE as an image file and print it out on a laser printer. If you don't own a laser printer you can always go to a copy store. Because the etching process is much more involved I've written a separate tutorial on the blog showing you the process, here (DIY PCB etching).
If you'd rather skip the etching process and you just so happen to be a fountain of patients you can solder the parts directly onto a pre-perforated board. To do this you have to have a clean work space and the right tools. Soldering this board took me around 4-5 hours but I imagine with a little more practice I could have it done in about half the time.
In this video you can see as I turn the potentiometer controlling the 555 timer's pulse i'm also changing the rate of the blinking LED. The although the 4017B(the larger chip on the board) is not hooked up in the video it does function and can sequence up to 10 LED's at one time.
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