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Minimalist 555 Line Follower — Parallax Forums

Minimalist 555 Line Follower

ercoerco Posts: 20,244
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?


Comments

  • ercoerco Posts: 20,244
    BTW, I've wondered if a 555 could line follow ever since Parallax's amazing LFO course in 2012, so I can die happy now.

  • Too bad you didn't think of this a few years ago when they had the 555 contest. Hans Camenzind even was one of the judges, if I recall.
  • ercoerco Posts: 20,244
    Forgive me, Ken: 555 timer vs. Propeller multicore. :)





  • ercoerco Posts: 20,244
    Jeff Haas wrote: »
    Hans Camenzind even was one of the judges, if I recall.

    Really? I would have liked to meet him!

  • Unfortunately the website for the contest is gone, but there are still articles about it up.

    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/
  • @erco, The cheaper you get, the better they run.

    Nice and smooth.

    You should be working for NASA or the military, they could be looking to save a few bucks.
  • kwinnkwinn Posts: 8,697
    MikeDYur wrote: »
    @erco, The cheaper you get, the better they run.

    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?
  • ercoerco Posts: 20,244
    Probably 200-400 Hz, depending on the lighting & photocells.
  • Nice! I want to make one, can you post the code?

    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.
  • ercoerco Posts: 20,244
    Ha, Yes, smooth. But no, can't turn too sharp, therefore the large radius. The photocells & LEDs are just hanging out in the breeze and the voltage differential isn't that great. Probably with some experimentation, isolation and aligning it could be improved.

    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?
  • erco wrote: »
    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 :)

  • ercoerco Posts: 20,244
    edited 2017-07-25 19:00
    Also uses two photocells. Cute.


  • ercoerco Posts: 20,244
    Drats. For rock-bottom minimalism, I still can't beat this one-motor, no electronics line follower. :(



  • The 555 timer is a fun IC to play with. I submitted an entry (555 Music Box Player) to the contest, which I found listed as one of the gems of the contest on the Evil Mad Science link/page below. Unfortunately my entry didn't make to the finals, but it was fun to participate anyway.
    Jeff Haas wrote: »
    Unfortunately the website for the contest is gone, but there are still articles about it up.

    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/

  • erco wrote: »
    Drats. For rock-bottom minimalism, I still can't beat this one-motor, no electronics line follower. :(

    No electronics?
  • Seairth wrote: »
    erco wrote: »
    Drats. For rock-bottom minimalism, I still can't beat this one-motor, no electronics line follower. :(

    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.

  • ercoerco Posts: 20,244
    All mechanical.
  • I'm guessing two wheels, one on either side of the line? If one wheel gets on the line, it slips and causes the other wheel to pull back to center?
  • RaymanRayman Posts: 13,805
    Somehow, I have the feeling that erco has a Hugo (movie) automaton at home...
  • ercoerco Posts: 20,244
    Rayman wrote: »
    Somehow, I have the feeling that erco has a Hugo (movie) automaton at home...

    I still haven't seen that movie, so I can neither confirm nor deny these allegations of impropriety. :)
  • ercoerco Posts: 20,244
    Seairth wrote: »
    I'm guessing two wheels, one on either side of the line? If one wheel gets on the line, it slips and causes the other wheel to pull back to center?

    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!

  • Turns on a crayon... I find it comforting to know that something worse than turns in reverse exists.
  • ercoerco Posts: 20,244
    You can see the 3 white wheels turning on the red chassis' underside at 4 seconds into that "Trail Tracker" video.
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