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NEW BOE-BOT - Servos Not working — Parallax Forums

NEW BOE-BOT - Servos Not working

Allen_J4Allen_J4 Posts: 8
edited 2011-06-14 11:44 in Robotics
I received a new BOE-BOT last week, and got to ACTIVITY #3 CONNECTING TO SERVO MOTORS, using the instructions for the BOE Rev C, I followed the instructions on pages 42-45. I was using the supplied battery pack with fresh (1.6V) AA batteries. the jumper was set at the Vin position as stated on page 43. When attempting ACTIVITY #4 Centering the Servos - I get no response from the either servo, it doesn't matter which servo, using P12 or P13, The LEDs are set-up on the breadboard as the instructions indicate. I get the expected output on the LED, but absolutely nothing from the servos.

I have tried each servo, in each of the P12 and P13 sockets.

What advice do you have?

Comments

  • Martin_HMartin_H Posts: 4,051
    edited 2011-06-13 10:54
    A gotcha that has bitten me is having the servos plug turned 180 degrees on the header. The center pin is the voltage supply and one outside pin is the ground and the other is the signal pin. When you have them flipped around the servo won't do anything. The servo's black wire goes to ground and white (or yellow) goes to signal.

    If you have a digital multi-meter you could check the voltage of the center servo header pin to ground and make sure it is around six volts. It likely will be, but I always check voltage when something doesn't work as expected.
  • Allen_J4Allen_J4 Posts: 8
    edited 2011-06-13 11:03
    Thanks for the reply, I'm at work - it's at home, so I'll have to wait until I get there.

    I checked the wires - they're oriented correctly, but I didn't have small leads for my home DMM. I'll check the voltage when I get home.
  • Martin_HMartin_H Posts: 4,051
    edited 2011-06-13 11:21
    In complex systems independent unit testing is generally helpful to isolate a faulty sub-system. So you have a way to test the servo's independently? A friend with an RC car or airplane could help. That way you'll know if it is them or the BOEbot.
  • Allen_J4Allen_J4 Posts: 8
    edited 2011-06-13 12:23
    Thanks Martin,

    I'm heading home in a few. I'll check the output on the servo socket.
  • W9GFOW9GFO Posts: 4,010
    edited 2011-06-13 12:24
    Also, do make sure that you have fully turned on the power switch. It has two "ON" positions. The first powers the Stamp and the second powers the Stamp and the servos.

    Rich H
  • Martin_HMartin_H Posts: 4,051
    edited 2011-06-13 13:54
    Rich H, good point, that's bit me once too.
  • Allen_J4Allen_J4 Posts: 8
    edited 2011-06-13 14:52
    That is what just bit me. Thanks for all the answers. I spent 2-3 hours on this...
  • ercoerco Posts: 20,255
    edited 2011-06-13 17:05
    Actually, there is a 4th position on that switch too. Never, repeat NEVER switch in into that position. It's MUCH worse than crossing the Ghostbuster streams.
  • W9GFOW9GFO Posts: 4,010
    edited 2011-06-13 18:08
    erco wrote: »
    Actually, there is a 4th position on that switch too. Never, repeat NEVER switch in into that position. It's MUCH worse than crossing the Ghostbuster streams.

    Uh, actually, there is not. You are really workin' towards that fifth start aren't ya? :innocent:

    Rich H
  • ercoerco Posts: 20,255
    edited 2011-06-13 18:10
    Oh, Rich. You must have one of the OLD boards. ;)
  • Martin_HMartin_H Posts: 4,051
    edited 2011-06-13 18:21
    As an aside, a DMM would have shown there was no voltage to the center pin. So that test would have lead you to the answer.

    Erco, the fourth position switch is only on those boards with the revision number 1.41421356.
  • ercoerco Posts: 20,255
    edited 2011-06-13 23:00
    And revision number 3.1415926535897932384626433 !
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-06-14 11:44
    ON upside down is NO. So that's your answer.

    -- Gordon
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