Colored tape instead of punched tape

Discussion in 'General Electronics Chat' started by Robin Mitchell, Dec 17, 2009.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    Hi guys,

    I was wondering how to do this.
    I know that you can get the robots that follow a black line against a white background, how could i use this to my advatage so instead of having to punch card i could draw a thick black line?

    Thanks!
     
  2. BMorse

    Senior Member

    Sep 26, 2009
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    very simple, use some IR photodetectors with some IR LEDs, and hook them up to a LM339 comparator... It is best to use 4 pairs to determine how far off the line it is, use o sets on the left side of the line and a second set on the right, the line it is following should stay in the middle of both sets.... you can actually follow a dark colored line on a light backround or a light colored line on a dark background with this setup, I used this setup on my Cylindro robot (Cylindrical Line Following Drone).
     
  3. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    um, thats great but i just want to be able to detect a black line
    So, when a black line is detected it sends it to memory
     
  4. BMorse

    Senior Member

    Sep 26, 2009
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    then use three pairs, one pair (center) to detect the line, and the other pairs can be on each side to verify it is a line, set the 2 outside ones as wide apart as the line.
     
  5. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    is there any other way that is more simple?
     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    here is the simplest way you can hook up a Photodetector and IR led pair...

    [​IMG]

    with this you either get a High when no dark line is detected and a Low when dark line is detected......
     
  7. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    so then i want to invert the output to get a high on the detects
     
  8. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    also, how do i position the detector and emiter, is there a specific angle
     
  9. BMorse

    Senior Member

    Sep 26, 2009
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    No specific angle is necessary, just point both straight down, place the emitter close to the detector (about 1/4" apart worked good for me with 5mm sized LED + emitter pair), but you have to put some kind of barrier between the 2 so it only detects IR when there is reflection off the floor.
     
  10. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    great, acctually, its not the floor, its a roll of paper that has a grid, with each cell representing one bit of data :)
     
  11. BMorse

    Senior Member

    Sep 26, 2009
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    Oh, so you are building a "Player bot", similar to those player pianos that run off of punched rolls of paper.... actually I have a ton of IR proximity sensors that are used in printers for detecting the paper, that I used for a similar project... the IR emitter and the Photodetector is all in one package... you can find these IR sensors in many different types electronics.... floppy drives used to have one, printers definitely have a few for detecting paper... photodetector pair.jpg
     
  12. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    o, o, i have an old floppy drive
     
  13. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Years ago I worked for Texas Instruments. We had a mail bot that would follow an "invisible line" on the floor and deliver mail. If thet wanted the bot to stop they would just put a break in the line or have some kind of marker.


    They would have to repaint the line from time to time. When they did they placed a sign. "Do not step on the invisible line"! Maybe just my sense of strange humor but I always would chuckle when I read that. I grabbed a sign one day and had it for a while but it has become misplaced over the years.
     
  14. BMorse

    Senior Member

    Sep 26, 2009
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    You would probably need atleast 4 sets to control 2 motors, you will have a grid on the paper 4 squares wide, the first 2 control direction and power to one motor the other pair controls direction and power for the other motor.

    Player Bot GRID.gif
     
  15. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    why,

    all i need is the paper with the lines on to be fed through and when a line has been detected it does computy stuff with it (cant be bothered to get into detail).
     
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