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tank tread base for robot. — Parallax Forums

tank tread base for robot.

totcohandtotcohand Posts: 28
edited 2010-09-17 18:37 in Robotics
I am just looking to see if anybody has used this for a robot application. http://www.robotmarketplace.com/products/AB-70108.html

I imagine I would just use the power supply that comes with it, and then how do I hardwire it into my bs2. I have the homework board. As im sure you can tell, I am very new to this and would appreciate the help.
Also, if anyone has any suggestions of another base with treads that is relatively cheap.
Thanks!

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-12-11 20:24
    Please note that this platform cannot be skid-steered as it comes. The single motor does not allow for independent control of the two tank treads, though it seems they sell the dual-unit a little lower on the page. Take care.

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    Chris Savage
    Parallax Engineering
  • totcohandtotcohand Posts: 28
    edited 2008-12-11 21:59
    Thanks I saw that and would order the dual-gearbox also. I guess my question is that if there would be a signal wire coming from the gearbox that I could plug into my BS2 homework board, or how could I control the steering.
  • UghaUgha Posts: 543
    edited 2008-12-11 22:40
    I have the dual gearbox and its just two motors plugged into a configurable gear set.
    It's quite nice and the motors are very small and powerful.

    I'm interested in that tank tread base and may end up getting it in a couple months. I'll let you know if I do.

    In order to hook it to a BS2 you'll need an H-bridge. Usually these come in dual packages that will let you hook
    up two motors at once so it works out good.

    It'll take 2-3 (depending on how the h-bridge is configured) stamp pins per motor and the h-bridge will easily fit on
    the breadboard on the BOE or homework board.

    Try to get an H-bridge that'll take up to 2 amps but I've used one with a 1amp max with no problems... so far.

    Note: The motors are designed for 3volts. If you go higher (say the regulated 5volts on the BOE) then they'll be
    faster/more powerful... but you'll reduce the life of the motors to around 1/4th of what they are designed for.

    I use a 2 AA battery pack as a supply for the motors and it works well... although you can use a voltage divider or
    regulator to drop down the 5volt from the BOE/homework board.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-12-11 23:34
    The answer to your question is no…you would not connect the wires from the motors directly to the BASIC Stamp I/O pins. You would need a motor controller to handle the motors. The BASIC Stamp I/O pins would not be able to handle the current of the motors directly. You can find a variety of motor controllers that would work on our website.

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    Chris Savage
    Parallax Engineering
  • totcohandtotcohand Posts: 28
    edited 2008-12-12 15:37
    Thank you chris and ugha for all your help. Looks like maybe ill just stick to the servos until I get a little more cash together. lol. Thanks again! this forum has been a great help!
  • WarumaWaruma Posts: 21
    edited 2010-09-15 21:43
    Chris Savage (Parallax) wrote: »
    The answer to your question is no…you would not connect the wires from the motors directly to the BASIC Stamp I/O pins. You would need a motor controller to handle the motors. The BASIC Stamp I/O pins would not be able to handle the current of the motors directly. You can find a variety of motor controllers that would work on our website.

    Chris Savage
    Parallax Engineering

    Hi Chris,

    If the BS2 cannot handle the current required of the motors, how does it do it normally using the PULSOUT commands? That current is still coming from Vdd of the BOE. Just curious.

    -Waruma
  • John R.John R. Posts: 1,376
    edited 2010-09-16 06:24
    You might also want to considder the "Rescue Crawler" http://www.robotmarketplace.com/products/0-TAM70169.html

    It includes the dual motor gear box, and has a few other parts :-)


    John R.
  • TimmooreTimmoore Posts: 1,031
    edited 2010-09-16 19:00
    I have used this base, I replaced the gearbox with the dual motor version. I also replaced the motors with these http://www.pololu.com/catalog/product/604

    The original motors use a low voltage (3V) but high current. An H-bridge for those is more expensive than the replacement motors which use a higher voltage (I used 7.2V) but lower current. I used a single L293D ($2-3) H-bridge to drive both motors.
    Not sure if you can drive a L293D directly with a stamp - I was using a prop.
    I have attached a picture of an early test with a prop board sat on top of the base.
    bots 015.jpg
    1600 x 1200 - 201K
  • W9GFOW9GFO Posts: 4,010
    edited 2010-09-17 18:37
    Waruma wrote: »
    Hi Chris,

    If the BS2 cannot handle the current required of the motors, how does it do it normally using the PULSOUT commands? That current is still coming from Vdd of the BOE. Just curious.

    That's not how it works. PULSOUT is used to control servos, not drive them. A servo has three wires; Power, Ground and Signal. The current to operate the servo's motor flows through the Power and Ground wires. The PULSOUT command, which tells the servo what to do, flows through the Signal and Ground wires. The only current that the BS2 supplies is the tiny amount required for the Signal.

    Rich H
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