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Servo Mismatched — Parallax Forums

Servo Mismatched

Daniel L.Daniel L. Posts: 7
edited 2009-07-25 16:43 in BASIC Stamp
The P13 Servo which controls the left wheel is too fast, way too fast. I tried reducing to to:

[noparse][[/noparse]code]
'.......
DO
·· PULSOUT 13, 793
'........
[noparse][[/noparse]/code]

With no effect

when I change it to.

[noparse][[/noparse]code]
'.......
DO
·· PULSOUT 13, 792
'........
[noparse][[/noparse]/code]

It curves left then. The servos are centered. They both are stopped at 750, I don't know whats wrong scool.gif .
·

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-25 00:03
    Servos are not matched although there shouldn't be large differences between two of the same model. What happens if you set them to run at near maximum speed (PULSOUT ---,500 or PULSOUT ---, 1000)?

    Do the servos have the same model number? How are they marked?
  • Daniel L.Daniel L. Posts: 7
    edited 2009-07-25 16:27
    Hmm? I thought max speed was 850 and 650...

    Oh thats weird... when p13 was set to 1000 and p12 to 500 it went perfectly straight. The boe bot book said max was either 650 or 850. Why does that happen?

    Oh and sorry for putting this in the wrong forum, I didn't see the boebot forum.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Daniel L.

    AKA, The Ninja of Frozen Milk
    AAKA, ゆきごくろさき (Yukigo Kurosaki )
  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-25 16:38
    Servos are designed to work with pulses from 1ms to 2ms in width. That corresponds to PULSOUT values of 500 to 1000 (see the Stamp Manual or Stamp Editor help file). Some servos will go as far as 0.5ms to 2.5ms, but not all. You have to experiment with an individual servo to find its limits.

    Continuous motion servos like the wheel servos on a BoeBot are actually modified standard servos with the position feedback mechanism disabled and the mechanical stops removed. They're not very precise things. I suspect that the BoeBot documentation talked about PULSOUT values of 650 and 850 because there's a 100 difference from the stop value of 750 and most of the speed change for the servo is close to the stop value. It's not linear.
  • Daniel L.Daniel L. Posts: 7
    edited 2009-07-25 16:43
    Huh... Well thank you very much Mike, you were a great help, now I can move on to instaling the whiskers.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Daniel L.

    AKA, The Ninja of Frozen Milk
    AAKA, ゆきごくろさき (Yukigo Kurosaki )
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