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Servo: Rotate, rotate, step, step, dead — Parallax Forums

Servo: Rotate, rotate, step, step, dead

ZackaryZackary Posts: 10
edited 2006-01-20 03:28 in General Discussion
Hi!
·· I'm wondering: Do the Parallax continuous servo·motors overheat? I know that when I start working with the motor it's fine. It rotates nicely. After a couple seconds the movement goes choppy. Then it stops altogether.
··· I'm a newbie, so I thought maybe it was code. So I left it to wait for help on forums. I just went back to it, and using the same code it works, rotates, chip, then dead. If I turn of power and wait a bit, it works, choppy dead. After a couple boots, it stops working at all.

·· Sound familar? If so please drop me a post. If you have any ideas, please drop me a post.

·· Also when it comes to calibrating the servo, I don't get it.·I set the pulse to 1.5ms for 20ms intervals, and change the potentiometer but whatever I rotate the potentiometer to,·the servo·never moves (maybe because it's already dead).

Thanks!

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-01-14 23:36
    Z.,

    · Let's see your program (not ALL of it, just the servo part.)
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-01-15 04:37
    How are you powering the servo?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • bulkheadbulkhead Posts: 405
    edited 2006-01-15 08:08
    First, make sure your servo isn't running off your stamp's power. Your servo should only have its signal(white wire) hooked up directly to the stamp.

    Next, check to see if your power source has enough power. Try using fresh batteries if you are using batteries. Also, try running just one servo at a time. Some non-rechargeable AA's can't supply enough current to run several servos at once, so your stamp may be resetting itself constantly when your power source's voltage drops below 5. It may also be a good idea to run the stamp and servos off separate power sources.

    Calibrating the servo should be simple. Once you get your servo to run continuously on a given signal (which you designate as your "neutral," stick a phillips screwdriver in the hole, and turn either left or right until the servo stops (or usually, you will over turn it and it will reverse direction). There's probably only a half turn of the potentiometer between full speed clockwise and full speed CCW (although you can turn the potentiometer several times in either direction, I believe).

    From your description, it does not sound like the servo is dead. These servos are pretty durable, and if they burn out (due to severe overheating), they won't work at all, ever again. I've never had a servo malfunction and not work, and then have it work after another try. If it burns out, it will smell bad too.
  • CJCJ Posts: 470
    edited 2006-01-15 15:46
    lets not forget the common ground between the stamp and servo

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    Who says you have to have knowledge to use it?

    I've killed a fly with my bare mind.
  • ZackaryZackary Posts: 10
    edited 2006-01-16 22:37
    I have the microcontroller connected to the same power supply as the servo. The power supply is that from a computer, so I doubt there's a problem with power comsumption or lack thereof.

    Something I noticed is that the behaviour of the servo at home and at school is different. At home, when the signal wire is disconnected (i.e. not to power or ground), the servo usually doesn't move. When I'm at school, if I disconnect the signal, it continually rotates. What's going on?

    I checked the signal coming out of my microcontroller with a 'scope. It is 1.25 ms pulse, with a total period of 20ms. It's not resetting (I used an LED to check everytime it resets).

    Post Edited (Zackary) : 1/17/2006 9:46:15 PM GMT
  • ZackaryZackary Posts: 10
    edited 2006-01-18 19:40
    It seems that when the servo pic picks up noise from another pin, it rotates 20 degrees every second. The pin that it's picking up the noise is set to pulse for about 5 us every second.

    Any ideas?
  • rockin_rickrockin_rick Posts: 32
    edited 2006-01-18 22:47
    Your output to the servo isn't on ra.4 is it? (you're using a PIC 16F877 or similar, right?) Regardless, have you tried a different output pin?

    Rick
  • ZackaryZackary Posts: 10
    edited 2006-01-20 03:28
    Rick,
    ·· Yes, PIC16F877A. No I'm not using RA4. Thanks a ton for the idea of changing pins. It works now. I was testing on RB7, but my PIC Board uses RB7 for programming or something. Changing to RB5 makes it work.

    Thanks!
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