I get a lot of email with requests to build circuits for people. Most are more than I would want to take on for a simple Hack A Week project without some monetary compensation but this one was unique. The email tells the story.
“Hey Dino,
I love your site and have a request if you are taking them. I’m member of a small volunteer fire dept. I’ve talked to many members of many fire depts over the years and they are always talking about where to get reasonably priced emergency response lights like Whalen or Code3 makes (they run in the hundreds of dollars from these companies). In our state the lights would be flashing red LED’s.
I think it would be great idea if you could show how to build a relatively inexpensive set of flashing lights (if possible) – even better if they can have variable flash patterns.
We don’t make any money and we don’t receive any equipment for personal vehicles, so being able to make our own would be a great benefit to our cause.
Thanks for taking the time to read this and all the great videos!”
How could I turn that one down? My first thought was to use the venerable 555 timer because it’s readily available and easy to use. Since I wanted two banks of lights to flash alternately I could use two 555s in astable mode and drive one of them with pin 3 when it’s off and goes low to ground. The first 555 would be driven by another 555 in astable mode oscillating at the rate of 1 hz.
Once again I referenced Rob Paisley’s awesome 555 timer page where you’ll find all kinds of info and applications for the 555.
I’ll post the final schematic, a PCB layout and a parts list in part 2 next week.
It all becomes clear in the video.
Keep on hackin!