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BS2 and servos at 6V: acting weird — Parallax Forums

BS2 and servos at 6V: acting weird

iamscottymiamscottym Posts: 30
edited 2006-04-22 15:29 in BASIC Stamp
I bought some futaba servos for a robot I'm building, and they say they can run at 6V. So I hooked them up to 6v on the BOE, and tried using a pseudo stepper program that I had been using at 5V with no problems. Basically it sends the servo all the way to the right, normal pulse, and then steps it back to the left.

When I tried it on 6v, the servo went to the right(really fast), and that was it. Reset didnt do anything either, even after moving the servo to the left so that it could go right, and then step left.

What's up with this?

Thanks,
iamscottym

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-04-22 04:27
    Just a quick question... Are the GND (Vcc) connections shared between your servo and the BOE?

    If the grounds are not connected, and the circuit is susceptible to 60Hz noise, the servo could
    behave this way.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • iamscottymiamscottym Posts: 30
    edited 2006-04-22 05:00
    I'm not sure what you mean. Sorry, I'm new at this. I see Vcc on above p15 next to the stamp, and i saw Vcc on the schematic, but I dont see how it'd be connected to the servo. I had a p15 signal wire to the servo, Vdd and Vss were connected to a separate battery from the BOE.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-04-22 05:05
    There needs to be at least 2 connections to the servo when running seperate power supplies.

    1) the signal line to the servo
    2) the ground connection between the servo's ground connection, and the controller's ground connection.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • iamscottymiamscottym Posts: 30
    edited 2006-04-22 05:11
    ah, it works. Thanks
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-04-22 05:38
    Glad that helped.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • iamscottymiamscottym Posts: 30
    edited 2006-04-22 05:41
    Hmm...seemed i stripped the gears...should this have happened? its a futaba s3101 micro servo, running no load. servo position 200-1200. i put it on a loop to go right, then left, then center and had it going for maybe a minute.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-04-22 06:21
    "Hmm...seemed i stripped the gears...should this have happened?"
    Without the grounds connected, it could have.

    200 seems to low...Even using BS2 at 2uS resolution this equates to 400uS.
    On the high side, if you are using a value of 1200 @ 2uS resolution, the resultant pulse
    will be 2400uS ...This is also to high. The "safe" range is between 1000uS and 2000uS.
    At 2uS resolution, the values should be 500 to 1000 on the BS2. If you have a faster
    BS2 with .8uS resolution, then these numbers should range from 1250 to 2500 on the
    BS2.

    Can you post your code?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • iamscottymiamscottym Posts: 30
    edited 2006-04-22 15:29
    The grounds were only disconnected for a few runs- with the old prog.

    DO
    FOR counter=1 TO 100
    PULSOUT 15, 1200
    PAUSE 20
    NEXT

    FOR counter=1 TO 20
    PULSOUT 15, 200
    PAUSE 20
    'NEXT

    FOR counter=1 TO 20
    PULSOUT 15, 800
    PAUSE 20
    NEXT


    LOOP
    END
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