Minimalist 555 Line Follower
I successfully combined three of my recent passions into one tonight: cheap line follower robots, the magnificent 555 timer, and using copious amounts of alarmingly cheap Ebay China parts. I've been saying for ages that we're foolish for not using 4-cent 555 timers and multiple nickel photocells in every project. Well, that's nearly all I used here. I hacked one of the $5 Ebay line follower kits. Tossed the 393 comparator, two trimpots, two driver transistors, and four resistors. Now one 555 does it all: reads two photocell line sensors and drives two motors. Minimalism rules. Beau & PhiPi et al: any way to do it cheaper yet?
![](https://img.youtube.com/vi/4Ysq47gt8t8/0.jpg)
![](https://img.youtube.com/vi/4Ysq47gt8t8/0.jpg)
Comments
Really? I would have liked to meet him!
Evil Mad Science helped judge the early rounds. Hans and Forrest Mims were final-round judges!
http://www.evilmadscientist.com/2011/some-gems-from-the-555-contest/
Then a year later Make had a retrospective after Hans passed away:
http://makezine.com/2012/08/22/555-timer-contest-highlights/
Nice and smooth.
You should be working for NASA or the military, they could be looking to save a few bucks.
Amazingly smooth for such a simple circuit. any idea what frequency the 555 is toggling at?
Seriously though, I love the simplicity, but wasn't expecting it to be as smooth as it was.
The S3 in your video sounds like a mad rooster.
What's funny is that all these parts have been around since 1972. Why weren't there $5 robot line follower kits when I was growing up?
No eBay China, no $5 anything
No electronics?
I had to look it up. Here's a hint, you have to use a smooth surface, like the included board, and something waxy like a crayon to draw the line.
I still haven't seen that movie, so I can neither confirm nor deny these allegations of impropriety.
Very good! Actually 3 wheels, all gear linked. One wide rear roller/wheel driving forward and two front rollers, rolling sideways in opposite directions straddling the line. The waxy crayon line is much stickier than the plastic mat, so that friction differential guides the car. Pretty slick mechanical stuff, circa 1977. The 555 timer was just 5 years old, and photocells (electric eyes!) were plentiful then. My cheap & cheesy method coulda been a contender!