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Need For Speed — Parallax Forums

Need For Speed

StampedeStampede Posts: 3
edited 2005-11-23 22:34 in BASIC Stamp
Hi All,

I just discovered the Basic Stamps. Great stuff.
I have a project in mind and I wonder if the Stamps can help me. I want to rotate a mirror (10 x 10 cm / 4 x 4") around an axis. The mirror should move about 15 degrees, then·a contact is closed and after a respons·the next move of 15 degrees begins. This·seems very·simple, but I want to do this five times a second :-).
So the mirror should move 15 degrees in 0.1 second and be motionless for the next 0.1 second before it moves again.
The standard servo seems to slow (1.5 sec for 180 degrees) but the mini servo might do it (0.5 sec for 180 degrees). The mirror will be able to move very light, so it's only a matter of starting and stopping the mass of the mirror.
I wonder if this will work, taking into account the processing time of the Stamp. Can anyone·hint on·what Stamp and motor I should use? I was planning to go with the USB Education board.
Any input very much appreciated.

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-11-23 21:35
    You might want to try a stepper motor -- it will give you control over the rotation and by knowing the number of steps you're going to rotate in each part of the sequence, you can be tidy with the code and I think you'll be able to pull it off. We have demo code for stepper motors on our web site (attached to our stepper) and in the StampWorks book.

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    Jon Williams
    Applications Engineer, Parallax
  • StampedeStampede Posts: 3
    edited 2005-11-23 22:02
    Thanks Jon,
    I much appreciate your help.

    So If I would purchase the USB "Basic Stamp Discovery Kit":
    http://www.parallax.com/detail.asp?product_id=27807
    and two stepper motors:
    http://www.parallax.com/detail.asp?product_id=27964
    then it would basically work? Or do I need an additional "Motor Controller"? I want to use two motors to rotate around X- and Y-axis but only move one at a time.
    Sorry for maybe asking the obvious but I'm totally new to this (except for Lego Robotics and Visual Basic).

    Thanks,
    Philip
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-11-23 22:07
    You don't have to use a specialized controller, but you do need a driver -- steppers use a lot of current and you can't connect them directly to the BASIC Stamp. If you want to go direct drive you can use the ULN2803 (would let you handle unipolar two motors) or the L293D (just on motor, but it could be unipolar [noparse][[/noparse]5/6 wire] or bipolar [noparse][[/noparse]4 wire]).

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    Jon Williams
    Applications Engineer, Parallax
  • StampedeStampede Posts: 3
    edited 2005-11-23 22:32
    Thanks again Jon,

    I'll go with the ULN2803 and the two unipolar stepper motors. If I search the Parallax site for ULN2803 I find the "ULN2803A Darlington Array" and I suppose that is what you mean. The pdf on the page seems to indicate in this direction smile.gif.

    Thanks for your help!
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-11-23 22:34
    That's the ticket. Just keep your pins on Nibble alignments (i.e., OUTA, OUTB, etc.) and it will be no trouble at all to control two motors.

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    Jon Williams
    Applications Engineer, Parallax
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