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Need Help determining if Parallax Servos is working ... — Parallax Forums

Need Help determining if Parallax Servos is working ...

sealion99sealion99 Posts: 23
edited 2011-12-04 18:07 in General Discussion
I have both a standard & continuous Parallax servo and am having some trouble getting them to work properly. I'm just trying to get them to respond properly to a basic 1.5ms pulse to start (sent continuously with an approx. 20ms wait between pulses). Attached is a scope trace of the pulse.

Here's what's happening -- the standard servo moves CW to the far right stop and holds, the continuous servo moves slowly CW. I cannot adjust the continuous to STOP with the trimpot. I can get it to slow down, but not STOP. Can't get much change in operation if I vary the pulse width.

I am driving with a TI MSP430 controller running at 3.5V. The HI on the output pin that I'm driving the SERVO with is approx. 3.5V. I'm powering the servo from a bench power supply at 5.5V.

Just want to verify if these SERVOS are any good at this point.

Appreciate any help.
bmp
bmp
ServoPulse -- 1.5ms.bmp
2M

Comments

  • PublisonPublison Posts: 12,366
    edited 2011-12-04 13:32
    The scope is showing a 2.46ms period. Are you sending a 20ms period?
  • PropabilityPropability Posts: 142
    edited 2011-12-04 14:30
    The pulse on the scope looks good (1.5 ms) . Are ALL the grounds common? The centering pot on the continuous is a little touchy to say the least.
  • sealion99sealion99 Posts: 23
    edited 2011-12-04 15:58
    Yes, I have a 1.5ms pulse with a 20ms wait between. I think the problem might be the ground reference. I have not specifically connected the grounds from my bench power supply & the MSP430 LaunchPad board, which is getting it's power from the computer USB. Let me try that and see what I get. Appreciate the help.
  • sealion99sealion99 Posts: 23
    edited 2011-12-04 16:48
    The ground was the problem. Both SERVOs are working fine now. Appreciate the help.
  • PublisonPublison Posts: 12,366
    edited 2011-12-04 18:07
    sealion99 wrote: »
    The ground was the problem. Both SERVOs are working fine now. Appreciate the help.

    Good Deal! Thanks for the report back. That could help people in the future.
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