|Blink On! Blink Off!|
I built one of these as a kid from a different article in MR, and it ran off of a 9 volt battery. A friend helped me build it, and I remember it has a potentiometer which allowed you to adjust the rate of the blinking. I wanted to do it again but couldn't find the article, and a call for help on the MR online forum didn't produce the article. If you know what article it was, please let me know. So, I went with a different design using a LM 3909 circuit chip. They are not manufactured anymore in the USA, but I found a couple on Ebay for $3 each and bought them from China. Very cheap, but shipping took a month and a half.
While reviewing the circuit diagram I found an error in the MR article. The diagram showing the LED has the polarity (+ and -) notations correct but the length of the anode and cathode reversed. Trust the polarity as indicated and not the length of the LED prongs. I used a small project board to make everything cleaner and mounted it all in a boxcar that I had lying around. I cut a gap in the bottom of the boxcar for the circuit to stick out from, as I didn't want to have it permanently mounted to the boxcar's body should I need to get inside. It isn't a perfect scale model of a EOD, but it does demonstrate my electrical abilities. I love cabooses but I may actually purchase a D&H decorated boxcar to use for times when I want to ... shudder... model a period train when cabooses weren't used anymore.