Shop OBEX P1 Docs P2 Docs Learn Events
GuiBot & HiTec Servos — Parallax Forums

GuiBot & HiTec Servos

Joseph OsborneJoseph Osborne Posts: 13
edited 2008-11-13 15:44 in Robotics
I have built a sort of a BoeBot using two HiTec HS-300 servos that I hacked myself. When I use GuiBot to run it the servos turn backwards. Why is this? Can I change the rotation direction from within GuiBot?

Joseph Osborne

PS- GuiBot is a wonderful tool for Middle School classroom use. I would love to see its capabilities expanded.

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-15 23:22
    What happens if you switch the servos so that the left one is connected to where the right one was, and the right one is connected to where the left one was?· That should reverse both servos and correct your problem.



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Joseph OsborneJoseph Osborne Posts: 13
    edited 2004-09-16 00:55
    The left and right won't match the Test display on the GuiBot but it might work. I'll try that.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-16 16:11
    Joseph,

    · I maybe should've clarified...I have seen two BOE-Bots put together where the user was unaware of the connections for left/right servos, and thus had them backward, making the servos both turn backward.

    ·· To save you undo messing around, I should've asked if you can control the left/right servos independently, so that when you control just the left servo, it turns, even if not the right direction.

    ·· In my examples above, the test code for each independent wheel turned the opposite side, which turned it the wrong way as well...That is a sign of reversed connections.· I apologize for typing without thinking/clarifying...



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Joseph OsborneJoseph Osborne Posts: 13
    edited 2004-09-17 23:36
    Nope. Doesn't work. Either Forward and backward are reversed or the Left and right turns are reversed. Are Futaba hacked servos different from HiTec hacked servos?

    Or is there a bug in GuiBot?

    Joseph Osborne
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-18 00:32
    The other possibility is that when you hacked them you missed something?· A good way to tell,is to try the test WITHOUT the GUIBot software.· Just try writing some BS2 code to move the servos,and see if you get the expected results.



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Joseph OsborneJoseph Osborne Posts: 13
    edited 2004-09-18 01:35
    Thanks Chris.

    These servos worked fine with the BoeBot Maze Rover program. The bot behaved as expected. But the GuiBot program is giving trouble. I wish there were a 'switch dirrection' switch like on the back of a transmitter.
    Do the Parallax tech people monitor this forum or do I need to contact them directly?


    Joseph Osborne
  • Jonny555Jonny555 Posts: 46
    edited 2004-09-18 04:31
    Search for "servo reversing' and you'll find alot of info. I believe that there are special circuits sold that reverse servos, but by simply opening the servo up and inversing the leads attached to the servo motor and the pot, the diretion will be reversed.

    Slow loading pdf i found after a google search: http://www.glide.dyndns.org/on-the-wing4/ServoReversing.pdf


    "Servo reversing is accomplished by reversing the power wires to the motor and by reversing the two outer leads on the potentiometer."
    Taken from: http://www.alansmodels.com/links/tom_younger/servo.htm

    Jonny

    Post Edited (Jonny555) : 9/18/2004 4:34:26 AM GMT
  • Joseph OsborneJoseph Osborne Posts: 13
    edited 2004-09-22 02:58
    Thank you all for your advice.

    I have reversed the motor leads and the bot works OK, at least in Basic mode. I just don't think I should have to do that just because I am using HiTec rather than Futaba servos.

    Joseph Osborne
  • Jonny555Jonny555 Posts: 46
    edited 2004-09-22 14:56
    Futaba and Hitec servos are the same. I have tested the futaba and Hitec servos I have and they rotate in the same direction. All depends what signal they receive.
  • Joseph OsborneJoseph Osborne Posts: 13
    edited 2004-09-23 00:50
    That's interesting. I can't think of any way one could reverse servo direction by hacking. I installed 20 turn 5K pots so I could adjust the null point also, and they work fine.

    The mystery deepens...

    I'm very surprised that no-one from Parallax has weighed in on this.
  • jakjrjakjr Posts: 88
    edited 2004-09-23 06:27
    Most all servos regardless of brand will work the same, The only difference between a futaba servo and a hitec servo (other than the obvious) is that a futaba servo has a polarity tab on the connector which can be filed off if needed.

    As far as I know the only exception is airtronics brand equipment, some of their stuff is reverse polarity. IE rather than the wire order being "ground, hot, signal" it is "hot, ground, signal".

    Your problem is probobly just caused by a simple software error, not by the choice of brand.
  • LAWMANLAWMAN Posts: 4
    edited 2008-10-18 03:58
    · The direction of rotation can vary depending on the manufacturer and type.· Example: My Futaba servo turns differently from the Hitec.· My·Hitec spec says that the servo will turn clockwise for a pulse of 1500us to 1900us( 1.5ms to 1.9 ms).
  • MovieMakerMovieMaker Posts: 502
    edited 2008-11-13 15:44
    May be a silly question, but did you think to calibrate the servos?
Sign In or Register to comment.