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Servo troubles — Parallax Forums

Servo troubles

ArchiverArchiver Posts: 46,084
edited 2001-10-01 15:07 in General Discussion
I am using a simple Hitec servo with a BS2. I have the serial line of
the servo on p7, and supplying 6v from a separate power supply. I am
connecting the ground line from the servo supply to Vss of the Stamp
circuit as recommended in the manual.

Using the following:

again:
pulsout 0,200 ' or for that matter any value from 100 to 200
pause 15
goto again

all that happens is that the servo goes fully to -45 position, even
though it should go to +45 and keeps humming rapidly. The current on
the external supply jumps to .58A!!

When I bring p7 low, the servo relaxes and stay in position, and of
course the current drops to 0.

Please help! is the problem the code? is it the wiring?

thanks

Al Najjar

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2001-10-01 06:14
    Your servo is moving all the way in one direction and banging against the
    stop. Not good for the servo. This means your numbers for the PULSOUT
    statement are not correct.

    According to the Stamp manual, a BS2 outputs a 2 microsecond (.000002
    second) pulse for every unit in the pulsout command. Most servos need a 1.5
    millisecond (.0015 second) pulse to move to the center position.

    With this in mind dividing .0015 by .000002 gives you 750. This means a
    value of 750 should move the servo to the center position. This value may
    vary as the timing on the Stamp and the servo will vary.

    What I do is power off the servo and turn it by hand all the way in both
    directions, making note of the position. I then figure out where the center
    position should be and juggle the PULSOUT value to center the servo.
    Original Message

    > I am using a simple Hitec servo with a BS2. I have the serial line of
    > the servo on p7, and supplying 6v from a separate power supply. I am
    > connecting the ground line from the servo supply to Vss of the Stamp
    > circuit as recommended in the manual.
    >
    > Using the following:
    >
    > again:
    > pulsout 0,200 ' or for that matter any value from 100 to 200
    > pause 15
    > goto again
    >
    > all that happens is that the servo goes fully to -45 position, even
    > though it should go to +45 and keeps humming rapidly. The current on
    > the external supply jumps to .58A!!
    >
    > When I bring p7 low, the servo relaxes and stay in position, and of
    > course the current drops to 0.
    >
    > Please help! is the problem the code? is it the wiring?
  • ArchiverArchiver Posts: 46,084
    edited 2001-10-01 13:08
    The pulse width given in some books is not wide enough. I have found that my
    Futaba servos need from a pulsout signal from 180 to 1170 for full motion.
    Try this code to test your servo. Hope it works for you!


    'Servo signal on pin 7
    'Fully CW = 180
    'Fully CCW = 1170



    'Variables & Constants
    Counter Var Byte
    Position Var Word
    ToServo Con 7

    '*********************Main Program

    Start:

    For Position = 180 To 1170 Step 20
    Pulsout ToServo, Position
    Pause 15
    Next

    For Position = 1170 To 180 Step 20
    Pulsout ToServo, Position
    Pause 15
    Next

    Goto Start


    Original Message
    From: brownstamp@y... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=bZxp9TJeFfX1CTIhnTVzMtCpWwQGNZfvyOWxd6LilfjchYdRFgPho7CFF1rw5raQj4IogcaIyoUOZg]brownstamp@y...[/url
    Sent: Sunday, September 30, 2001 11:49 PM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] Servo troubles

    I am using a simple Hitec servo with a BS2. I have the serial line of
    the servo on p7, and supplying 6v from a separate power supply. I am
    connecting the ground line from the servo supply to Vss of the Stamp
    circuit as recommended in the manual.

    Using the following:

    again:
    pulsout 0,200 ' or for that matter any value from 100 to 200
    pause 15
    goto again

    all that happens is that the servo goes fully to -45 position, even
    though it should go to +45 and keeps humming rapidly. The current on
    the external supply jumps to .58A!!

    When I bring p7 low, the servo relaxes and stay in position, and of
    course the current drops to 0.

    Please help! is the problem the code? is it the wiring?

    thanks

    Al Najjar


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  • ArchiverArchiver Posts: 46,084
    edited 2001-10-01 15:07
    when the current jumps to that high I believe that you have stalled out the
    motor/geartrain against a mechanical stop. I don't know what numbers to tell
    you to use but stay away from the pulse width that stalls out the motor in
    either direction.

    richard

    Original Message
    From: "Dennie Bishop" <dbishop@e...>
    To: <basicstamps@yahoogroups.com>
    Sent: Monday, October 01, 2001 7:08 AM
    Subject: RE: [noparse][[/noparse]basicstamps] Servo troubles


    > The pulse width given in some books is not wide enough. I have found that
    my
    > Futaba servos need from a pulsout signal from 180 to 1170 for full motion.
    > Try this code to test your servo. Hope it works for you!
    >
    >
    > 'Servo signal on pin 7
    > 'Fully CW = 180
    > 'Fully CCW = 1170
    >
    >
    >
    > 'Variables & Constants
    > Counter Var Byte
    > Position Var Word
    > ToServo Con 7
    >
    > '*********************Main Program
    >
    > Start:
    >
    > For Position = 180 To 1170 Step 20
    > Pulsout ToServo, Position
    > Pause 15
    > Next
    >
    > For Position = 1170 To 180 Step 20
    > Pulsout ToServo, Position
    > Pause 15
    > Next
    >
    > Goto Start
    >
    >
    >
    >
    Original Message
    > From: brownstamp@y... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=EF8PS7kbDUvVOR_EiVPJp1yOyFR5x9SGCbncoNR5oLTFDbva6n56gZgqaD8sHTBSOxe1wavg13NEedtDjsu-]brownstamp@y...[/url
    > Sent: Sunday, September 30, 2001 11:49 PM
    > To: basicstamps@yahoogroups.com
    > Subject: [noparse][[/noparse]basicstamps] Servo troubles
    >
    > I am using a simple Hitec servo with a BS2. I have the serial line of
    > the servo on p7, and supplying 6v from a separate power supply. I am
    > connecting the ground line from the servo supply to Vss of the Stamp
    > circuit as recommended in the manual.
    >
    > Using the following:
    >
    > again:
    > pulsout 0,200 ' or for that matter any value from 100 to 200
    > pause 15
    > goto again
    >
    > all that happens is that the servo goes fully to -45 position, even
    > though it should go to +45 and keeps humming rapidly. The current on
    > the external supply jumps to .58A!!
    >
    > When I bring p7 low, the servo relaxes and stay in position, and of
    > course the current drops to 0.
    >
    > Please help! is the problem the code? is it the wiring?
    >
    > thanks
    >
    > Al Najjar
    >
    >
    > To UNSUBSCRIBE, just send mail to:
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    > from the same email address that you subscribed. Text in the Subject and
    > Body of the message will be ignored.
    >
    >
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    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject and
    Body of the message will be ignored.
    >
    >
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    >
    >
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