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Boe Bot going backwards — Parallax Forums

Boe Bot going backwards

william chanwilliam chan Posts: 1,326
edited 2009-05-03 21:39 in Robotics
Help!

Can I assume that the PING))) sensor is the front end of the Boe-bot?
Everytime I call GOSUB pulse_forward the robot goes in reverse.
When I call GOSUB Back_Up the bot moves forward.

Is there something wrong with the way I assembled the boe-bot?

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www.fd.com.my
www.mercedes.com.my

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-29 14:34
    You may have the servos connected to the wrong I/O pins. If the left and right servo cables are reversed, that would reverse the robot direction. Try swapping them.
  • ManetherenManetheren Posts: 117
    edited 2009-04-29 20:04
    Also the robot is considered to be going forward when the little wheel is in the back. I personnaly have it going the other way.

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    Tia'Shar Manetheren
  • william chanwilliam chan Posts: 1,326
    edited 2009-04-30 00:57
    Mike,

    You are right. After swapping the left and right connections, the robot is going forward correctly now.

    But it's movement is jerky. Seems like the BS2 cannot move all the servos at the same time.

    Now I wish Parallax has come up with a Propeller based Boe Bot, or do I have to make my own board?

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    www.fd.com.my
    www.mercedes.com.my
  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-30 01:34
    The BS2 can move several servos (like 2 or 3) at the same time without jerkiness if the code is written carefully. The movement is probably jerky because the BS2 is not producing servo control pulses fast enough. There are probably PAUSEs there in the program that should be shortened.

    You can certainly do a Propeller-based BoeBot using a Propeller Protoboard with the accessory kit. BoeBotBasic (in the OBEX) was developed for just that purpose. You can even use a SpinStamp on the BoeBot. If so, I'd recommend putting 1K resistors in series with the servo control lines. That's how BoeBotBasic was originally developed (with a SpinStamp).
  • william chanwilliam chan Posts: 1,326
    edited 2009-04-30 03:00
    What is the purpose of the 1k resistors?

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    www.fd.com.my
    www.mercedes.com.my
  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-30 03:44
    1) Motors generate noise, even servo motors. This noise can feed back through the servo control line and the 1K resistors attenuate it if present without interfering with the control pulses coming from the Propeller. I think it was Beau that suggested this.

    2) There are plenty of sources of +5V on the BoeBot board. If you have a 1K resistor in series with the control line close to the SpinStamp and the control line accidentally gets shorted to the +5V supply, the 1K resistor will save your SpinStamp from going poof!
  • dandreaedandreae Posts: 1,375
    edited 2009-04-30 15:55
    william chan said...
    Mike,

    You are right. After swapping the left and right connections, the robot is going forward correctly now.

    But it's movement is jerky. Seems like the BS2 cannot move all the servos at the same time.

    Now I wish Parallax has come up with a Propeller based Boe Bot, or do I have to make my own board?

    Hi William,

    Parallax is coming out with a Propeller based robot.· Please check back in a few·months for more information.

    Kind regards,

    Dave

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    Dave Andreae

    Parallax Tech Support·
  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-30 19:23
    Here's the link to the thread on the Propeller BoeBot I made:
    http://forums.parallax.com/showthread.php?p=635533

    I had to add an I/O Expander (PCA9554) for the HM55B compass because I wanted to keep the VGA / mouse / keyboard / TV features available, but you could leave out one of these to handle the compass if you wanted.
  • W9GFOW9GFO Posts: 4,010
    edited 2009-05-01 01:48
    Dave Andreae (Parallax) said...

    Parallax is coming out with a Propeller based robot. Please check back in a few months

    Do you mean the Stingray or something similar in size to the BoeBot?

    Rich H
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-05-01 17:04
    The Stingray is what Dave was referring to. Information can be found on the following forum thread. Take care.

    http://forums.parallax.com/showthread.php?p=793913

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    Chris Savage
    Parallax Engineering
  • william chanwilliam chan Posts: 1,326
    edited 2009-05-02 01:35
    Why is it called a stingray when the wings are missing?

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    www.fd.com.my
    www.mercedes.com.my
  • NinjaTechNinjaTech Posts: 8
    edited 2009-05-02 09:43
    Try checking the programming of the subroutines.
    Make sure the servo values are correct.
  • slamerslamer Posts: 52
    edited 2009-05-03 21:39
    I noticed the same thing with the BOE bot. It can get a bit jerky when it is trying to send the PWM signal and read sensors or even radio signals. Keeping in mind that processors only do one thing at a time. I added a PSC servo control board to the BOE bot and let it send the signals to the drivetrain servos. This frees up the BASIC stamp2 to do other things like monitor switches or sensors. It's good to hear that the propeller chip will have a robot to learn with as well. Multiple processors solve a lot of problems.

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    undefinedundefinedundefinedundefinedSteven Kirk Nelson (slamer)
    Team K.I.S.S

    Post Edited (slamer) : 5/3/2009 9:45:54 PM GMT
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