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Servo problem — Parallax Forums

Servo problem

ArchiverArchiver Posts: 46,084
edited 2004-06-08 15:25 in General Discussion
I am trying to experiment with a servo motor (Hitec HS-300) on BS2
but
have the following problem:

when using the following simple programs;

again:
for b2=100 to 200
for b3 = 1 to 5
pulsout 0,b2
pause 15
next
next
goto again

which is supposed to drive it from one extreme end of the servo's
motion to the other in small intervals, I can only get the servo to
move in one direction. Even if I use it with the following;

For b2 = 1 to 10
pulsout 0,150 ' center it with 10 pulses
next

the servo still turns in the counter clock direction for 10 pulses
intead of being centered! Even if I substitue 150 with 200 which is
supposed to move the servo to the extreme clockwise position, the
server moves in the ccw direction!

Th servo comes with three wires: black = ground, red = +5v and
yellow
which is supposed to be the signal. I have the yellow going to line
0
on the BS2, the red to an external 5vdc source and the black goes to
both the ground from the external source and the BS2's Vss line.

any help?

thanks

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-08-22 05:37
    Your code would work with a BS1 which generates pulses in 10us units;
    however, the BS2 pulses in 2us units, so you should vary b2 from 500 to
    1000. Also, I believe the "standard" pulse rate for servos is 50 Hz, so you
    might try pause 20, but this may not be a problem.

    Ray McArthur

    Original Message
    From: <alnajjar@s...>
    To: <basicstamps@egroups.com>
    Sent: Monday, August 21, 2000 11:58 PM
    Subject: [noparse][[/noparse]basicstamps] Servo problem


    > I am trying to experiment with a servo motor (Hitec HS-300) on BS2
    > but
    > have the following problem:
    >
    > when using the following simple programs;
    >
    > again:
    > for b2=100 to 200
    > for b3 = 1 to 5
    > pulsout 0,b2
    > pause 15
    > next
    > next
    > goto again
    >
    > which is supposed to drive it from one extreme end of the servo's
    > motion to the other in small intervals, I can only get the servo to
    > move in one direction. Even if I use it with the following;
    >
    > For b2 = 1 to 10
    > pulsout 0,150 ' center it with 10 pulses
    > next
    >
    > the servo still turns in the counter clock direction for 10 pulses
    > intead of being centered! Even if I substitue 150 with 200 which is
    > supposed to move the servo to the extreme clockwise position, the
    > server moves in the ccw direction!
    >
    > Th servo comes with three wires: black = ground, red = +5v and
    > yellow
    > which is supposed to be the signal. I have the yellow going to line
    > 0
    > on the BS2, the red to an external 5vdc source and the black goes to
    > both the ground from the external source and the BS2's Vss line.
  • ArchiverArchiver Posts: 46,084
    edited 2000-08-25 22:10
    Thanks! It works fine. However, it turns very slowly even with a
    delay of 15 ms, which is the shortest delay that I can put in to make
    work properly. Do you think that this servo may need 8.3V instead of
    the 5 that I am providing? Otherwise, there is really no way to make
    the servo respond faster.


    Al




    --- In basicstamps@egroups.com, "rjmca" <rjmca@w...> wrote:
    > Your code would work with a BS1 which generates pulses in 10us
    units;
    > however, the BS2 pulses in 2us units, so you should vary b2 from
    500
    to
    > 1000. Also, I believe the "standard" pulse rate for servos is 50
    Hz, so you
    > might try pause 20, but this may not be a problem.
    >
    > Ray McArthur
    >
    >
    Original Message
    > From: <alnajjar@s...>
    > To: <basicstamps@egroups.com>
    > Sent: Monday, August 21, 2000 11:58 PM
    > Subject: [noparse][[/noparse]basicstamps] Servo problem
    >
    >
    > > I am trying to experiment with a servo motor (Hitec HS-300) on BS2
    > > but
    > > have the following problem:
    > >
    > > when using the following simple programs;
    > >
    > > again:
    > > for b2=100 to 200
    > > for b3 = 1 to 5
    > > pulsout 0,b2
    > > pause 15
    > > next
    > > next
    > > goto again
    > >
    > > which is supposed to drive it from one extreme end of the servo's
    > > motion to the other in small intervals, I can only get the servo
    to
    > > move in one direction. Even if I use it with the following;
    > >
    > > For b2 = 1 to 10
    > > pulsout 0,150 ' center it with 10 pulses
    > > next
    > >
    > > the servo still turns in the counter clock direction for 10 pulses
    > > intead of being centered! Even if I substitue 150 with 200 which
    is
    > > supposed to move the servo to the extreme clockwise position, the
    > > server moves in the ccw direction!
    > >
    > > Th servo comes with three wires: black = ground, red = +5v and
    > > yellow
    > > which is supposed to be the signal. I have the yellow going to
    line
    > > 0
    > > on the BS2, the red to an external 5vdc source and the black goes
    to
    > > both the ground from the external source and the BS2's Vss line.
  • ArchiverArchiver Posts: 46,084
    edited 2000-08-26 00:03
    Al:
    I am not familiar with the Hitec HS-300 servo, but there are many on this
    list with lots of servo experience...someone should be able to tell you what
    voltage it is designed for.

    Glad it's working, at least,
    Ray McArthur

    > Thanks! It works fine. However, it turns very slowly even with a
    > delay of 15 ms, which is the shortest delay that I can put in to make
    > work properly. Do you think that this servo may need 8.3V instead of
    > the 5 that I am providing? Otherwise, there is really no way to make
    > the servo respond faster.
    >
    > > I am trying to experiment with a servo motor (Hitec HS-300) on BS2
  • ArchiverArchiver Posts: 46,084
    edited 2000-08-26 15:53
    At 09:10 PM 8/25/00 -0000, Al wrote:

    >Thanks! It works fine. However, it turns very slowly even with a
    >delay of 15 ms, which is the shortest delay that I can put in to make
    >work properly. Do you think that this servo may need 8.3V instead of
    >the 5 that I am providing? Otherwise, there is really no way to make
    >the servo respond faster.

    Hi Al,
    I can't tell from this post what it is you're trying to do with the
    servo, it would help if you could post the entire code you are using now.
    Don't increrase the voltage to the servo, this will drastically reduce it's
    life (burn out the motor windings). For standard hobby servos 5v is
    correct. I don't know what you mean by '15ms delay'...is this the interval
    between the pulses you are sending to the servo? If so, it's a bit short,
    as servos expect a 50hz pulse train. This will also depend on what else you
    are getting your stamp to do. Adjusting this value will have no effect on
    how fast the servo turns in any case. To make the servo turn faster, you
    need to adjust the rate_of_change of the value you're using for the pulsout
    command. This will adjust how quickly the width of the pulses changes.

    ie.
    loop:
    x=x+10
    pulsout x
    goto loop

    will cause the servo to move at a rate five times faster than

    loop:
    x=x+2
    pulsout x
    goto loop

    Do you see what I mean? Of course, no matter how fast you change the
    pulsewidth there is an upper limit on how fast the servo will go. This is
    the transit time of the servo, usually indicated in degrees/sec in the
    documentation for your particular model.

    HTH, Duncan
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 01:29
    Original message from: "Al Williams" <alw@a...>
    >
    >Just connect the 6V ground to the Stamp's ground. Without it, you
    servo is
    >"floating". Presumably you are driving the Stamp from a 5V supply or
    a 9V
    >battery or something. Just hook the - of the 5V supply or the battery
    or the
    >Stamp's Vss pin to the - terminal of the 6V supply for the servo.
    >
    >Regards,
    >
    >Al Williams
    >AWC

    >--- RONNIE GODWIN
    >--- kb6rrt@e...
    >--- EarthLink: It's your Internet.
    >do you have all your grounds connected together ? >that might stop
    the
    >little jumps

    Thanks for your help! It's actually working now.


    Jason

    __________________________________________________________________
    Get your free Australian email account at http://www.start.com.au
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 13:40
    I'm new to this list and to the stamp, and a beginner to electronics,
    and I am hoping
    someone on this list can help me with some very annoying servo related
    problems that
    I have been struggling with.

    I have my Stamp 2, 6V 1A powersupply, and servo connected EXACTLY like
    this:







    pin 0
    | STAMP II |
    |SERVO |

    | |
    | |
    -| |+
    |POWER 6V |


    (no capacitors, resistors or diodes in the circuit at all)










    the code I'm running with this setup is:

    '

    servo:

    pulsout 0, 750 'servo centre position
    pause 15

    goto servo

    '


    I think this SHOULD centre the servo and hold it in that position, but
    what happens is the
    servo just keeps moving one way until it stops at the end of it's 180
    deg movement range.
    I thought maybe the servo had a badly positioned pot inside, but I
    have tried all different
    pulse lengths and pause lenghts and the servo still only moves in one
    direction and stops
    at it's limit of movement.

    One clue is that even when I remove the "pulsout" command from my code
    the servo
    still makes little jumps forward, very randomly. Perhaps it's being
    moved by some sort of
    noise in the circuitry or something?


    I'm also using a R/C hitec servo, instead of the more general futaba,
    but the sources on
    the net indicate that both types run on the same signal type, ie a
    1-2ms
    positive pulse every 20 ms.

    Does anyone know what's going on? Maybe I'm making some simple
    mistake?



    Also, would it be possible to run five or even ten servo's from just
    one stamp 2?
    It seems that if I keep the entire program loop time under 20 ms it
    should supply
    all the servo's with correctly timed pulses. Or is it impossible to
    control so many servos
    wit a single stamp for power reasons etc?


    sincerely,

    Jason

    __________________________________________________________________
    Get your free Australian email account at http://www.start.com.au
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 14:13
    > [noparse][[/noparse]Original Message]
    > From: Jason 1 <plugger2@s...>
    > To: basicstamps@egroups.com <basicstamps@egroups.com>
    > Date: 10/13/00 4:51:22 AM
    > Subject: [noparse][[/noparse]basicstamps] Servo Problem
    >
    > I'm new to this list and to the stamp, and a beginner to electronics,
    > and I am hoping
    > someone on this list can help me with some very annoying servo related
    > problems that
    > I have been struggling with.
    >
    > I have my Stamp 2, 6V 1A powersupply, and servo connected EXACTLY like
    > this:
    >
    >
    >
    >
    >
    >
    >
    >
    pin 0
    > | STAMP II |
    |SERVO |
    >

    > | |
    > | |
    > -| |+
    >
    > |POWER 6V |
    >
    >
    >
    > (no capacitors, resistors or diodes in the circuit at all)
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    > the code I'm running with this setup is:
    >
    > '
    >
    > servo:
    >
    > pulsout 0, 750 'servo centre position
    > pause 15
    >
    > goto servo
    >
    > '
    >
    >
    > I think this SHOULD centre the servo and hold it in that position, but
    > what happens is the
    > servo just keeps moving one way until it stops at the end of it's 180
    > deg movement range.
    > I thought maybe the servo had a badly positioned pot inside, but I
    > have tried all different
    > pulse lengths and pause lenghts and the servo still only moves in one
    > direction and stops
    > at it's limit of movement.
    >
    > One clue is that even when I remove the "pulsout" command from my code
    > the servo
    > still makes little jumps forward, very randomly. Perhaps it's being
    > moved by some sort of
    > noise in the circuitry or something?
    >
    >
    > I'm also using a R/C hitec servo, instead of the more general futaba,
    > but the sources on
    > the net indicate that both types run on the same signal type, ie a
    > 1-2ms
    > positive pulse every 20 ms.
    >
    > Does anyone know what's going on? Maybe I'm making some simple
    > mistake?
    >
    >
    >
    > Also, would it be possible to run five or even ten servo's from just
    > one stamp 2?
    > It seems that if I keep the entire program loop time under 20 ms it
    > should supply
    > all the servo's with correctly timed pulses. Or is it impossible to
    > control so many servos
    > wit a single stamp for power reasons etc?
    >
    >
    > sincerely,
    >
    > Jason
    >
    > __________________________________________________________________
    > Get your free Australian email account at http://www.start.com.au
    >
    >
    >
    >



    --- RONNIE GODWIN
    --- kb6rrt@e...
    --- EarthLink: It's your Internet.
    do you have all your grounds connected together ? that might stop the
    little jumps
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 15:00
    Hi Jason (hmm... Jason on Friday the 13th....)

    Do you have a common ground point between your 6V and the supply for the
    Stamp? How is the Stamp powered?

    You can run multiple servos at once, but as you point out, you rapidly get
    to the point where all you are doing is running the servos. Check out the
    link below to see our PAK-VIII which can run 8 servos at once without
    loading the Stamp at all. In fact, you can see it doing just that in our
    Stamp project of the month this month
    (http://www.al-williams.com/awce/som.htm).

    Regards,

    Al Williams
    AWC
    * Control 8 servos at once with the PAK-VIII:
    http://www.al-williams.com/awce/pak8.htm
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 15:33
    I wrote:
    >
    >I'm new to this list and to the stamp, and a beginner to electronics,
    >and I am hoping
    >someone on this list can help me with some very annoying servo
    related
    >problems that
    >I have been struggling with.
    >
    >I have my Stamp 2, 6V 1A powersupply, and servo connected EXACTLY
    like
    >this:
    >
    >
    >
    >
    >
    >
    >
    >
    pin 0
    >| STAMP II |
    |SERVO |
    >

    > | |
    > | |
    > -| |+
    >
    > |POWER 6V |
    >
    >
    >
    >(no capacitors, resistors or diodes in the circuit at all)






    My ascii picture didn't seem to make it intact, so I have made a gif
    of my circuit, perhaps this will help.








    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >the code I'm running with this setup is:
    >
    >'
    >
    >servo:
    >
    >pulsout 0, 750 'servo centre position
    >pause 15
    >
    >goto servo
    >
    >'
    >
    >
    >I think this SHOULD centre the servo and hold it in that position,
    but
    >what happens is the
    >servo just keeps moving one way until it stops at the end of it's 180
    >deg movement range.
    >I thought maybe the servo had a badly positioned pot inside, but I
    >have tried all different
    >pulse lengths and pause lenghts and the servo still only moves in one
    >direction and stops
    >at it's limit of movement.
    >
    >One clue is that even when I remove the "pulsout" command from my
    code
    >the servo
    >still makes little jumps forward, very randomly. Perhaps it's being
    >moved by some sort of
    >noise in the circuitry or something?
    >
    >
    >I'm also using a R/C hitec servo, instead of the more general futaba,
    >but the sources on
    >the net indicate that both types run on the same signal type, ie a
    >1-2ms
    >positive pulse every 20 ms.
    >
    >Does anyone know what's going on? Maybe I'm making some simple
    >mistake?
    >
    >
    >
    >Also, would it be possible to run five or even ten servo's from just
    >one stamp 2?
    >It seems that if I keep the entire program loop time under 20 ms it
    >should supply
    >all the servo's with correctly timed pulses. Or is it impossible to
    >control so many servos
    >wit a single stamp for power reasons etc?
    >
    >
    >sincerely,
    >
    >Jason
    >











    __________________________________________________________________
    Get your free Australian email account at http://www.start.com.au
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 22:08
    Just connect the 6V ground to the Stamp's ground. Without it, you servo is
    "floating". Presumably you are driving the Stamp from a 5V supply or a 9V
    battery or something. Just hook the - of the 5V supply or the battery or the
    Stamp's Vss pin to the - terminal of the 6V supply for the servo.

    Regards,

    Al Williams
    AWC
    * Floating point math for the Stamp, PIC, SX, or any microcontroller:
    http://www.al-williams.com/awce/pak1.htm


    >
    Original Message
    > From: Jason 1 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=sZRKGZpi9937B6D8dzSt_xlD1yMhehlTgoRvomFYXMe9bEtj4NMDx3ejUJ2Fztwen52_6GWRDzU96-8BKSElBQ]plugger2@s...[/url
    > Sent: Friday, October 13, 2000 5:28 PM
    > To: basicstamps@egroups.com
    > Subject: Re: [noparse][[/noparse]basicstamps] Servo Problem
    >
    >
    > Original message from: "Al Williams" <alw@a...>
    > >
    > >Hi Jason (hmm... Jason on Friday the 13th....)
    > >
    > >Do you have a common ground point between your 6V and the supply for
    > the
    > >Stamp? How is the Stamp powered?--- RONNIE GODWIN
    >
    > --- kb6rrt@e... wrote:
    > >--- EarthLink: It's your Internet.
    > >do you have all your grounds connected together ? >that might stop
    > the
    > >little jumps
    >
    > Thanks for your help guys.
    >
    > I have attached a small gif file showing the circuit I'm using,
    > because my original picture was scrambled.
    >
    > No, I do not have a common ground. How do I do this? What pins or
    > wires do I join together to get a common groud?
    >
    >
    > Jason
    >
    > __________________________________________________________________
    > Get your free Australian email account at http://www.start.com.au
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-13 23:28
    Original message from: "Al Williams" <alw@a...>
    >
    >Hi Jason (hmm... Jason on Friday the 13th....)
    >
    >Do you have a common ground point between your 6V and the supply for
    the
    >Stamp? How is the Stamp powered?--- RONNIE GODWIN

    --- kb6rrt@e... wrote:
    >--- EarthLink: It's your Internet.
    >do you have all your grounds connected together ? >that might stop
    the
    >little jumps

    Thanks for your help guys.

    I have attached a small gif file showing the circuit I'm using,
    because my original picture was scrambled.

    No, I do not have a common ground. How do I do this? What pins or
    wires do I join together to get a common groud?


    Jason

    __________________________________________________________________
    Get your free Australian email account at http://www.start.com.au
  • ArchiverArchiver Posts: 46,084
    edited 2000-10-14 05:37
    you MUST connect the ground of the servo's power source and the ground of
    the stamps power source, or the servo doesnt have any referance to know what
    voltage is feeding the pulse line.
    norm



    >From: Jason 1 <plugger2@s...>
    >Reply-To: basicstamps@egroups.com
    >To: "basicstamps@egroups.com" <basicstamps@egroups.com>
    >Subject: Re: [noparse][[/noparse]basicstamps] Servo Problem
    >Date: Sat, 14 Oct 2000 7:7 +1000
    >
    >I wrote:
    > >
    > >I'm new to this list and to the stamp, and a beginner to electronics,
    > >and I am hoping
    > >someone on this list can help me with some very annoying servo
    >related
    > >problems that
    > >I have been struggling with.
    > >
    > >I have my Stamp 2, 6V 1A powersupply, and servo connected EXACTLY
    >like
    > >this:
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    pin 0
    > >| STAMP II |
    |SERVO |
    > >

    > > | |
    > > | |
    > > -| |+
    > >
    > > |POWER 6V |
    > >
    > >
    > >
    > >(no capacitors, resistors or diodes in the circuit at all)
    >
    >
    >
    >
    >
    >
    >My ascii picture didn't seem to make it intact, so I have made a gif
    >of my circuit, perhaps this will help.
    >
    >
    >
    >
    >
    >
    >
    >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >the code I'm running with this setup is:
    > >
    > >'
    > >
    > >servo:
    > >
    > >pulsout 0, 750 'servo centre position
    > >pause 15
    > >
    > >goto servo
    > >
    > >'
    > >
    > >
    > >I think this SHOULD centre the servo and hold it in that position,
    >but
    > >what happens is the
    > >servo just keeps moving one way until it stops at the end of it's 180
    > >deg movement range.
    > >I thought maybe the servo had a badly positioned pot inside, but I
    > >have tried all different
    > >pulse lengths and pause lenghts and the servo still only moves in one
    > >direction and stops
    > >at it's limit of movement.
    > >
    > >One clue is that even when I remove the "pulsout" command from my
    >code
    > >the servo
    > >still makes little jumps forward, very randomly. Perhaps it's being
    > >moved by some sort of
    > >noise in the circuitry or something?
    > >
    > >
    > >I'm also using a R/C hitec servo, instead of the more general futaba,
    > >but the sources on
    > >the net indicate that both types run on the same signal type, ie a
    > >1-2ms
    > >positive pulse every 20 ms.
    > >
    > >Does anyone know what's going on? Maybe I'm making some simple
    > >mistake?
    > >
    > >
    > >
    > >Also, would it be possible to run five or even ten servo's from just
    > >one stamp 2?
    > >It seems that if I keep the entire program loop time under 20 ms it
    > >should supply
    > >all the servo's with correctly timed pulses. Or is it impossible to
    > >control so many servos
    > >wit a single stamp for power reasons etc?
    > >
    > >
    > >sincerely,
    > >
    > >Jason
    > >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >__________________________________________________________________
    >Get your free Australian email account at http://www.start.com.au
    >
    >
    ><< JasonsServoCircuit.gif >>

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  • ArchiverArchiver Posts: 46,084
    edited 2004-06-07 11:37
    hallo

    Take a look at mine servo.doc file in the files directory

    and please give some help




    Thanks for any suggestion
    Cyrill
  • ArchiverArchiver Posts: 46,084
    edited 2004-06-07 16:43
    Summary:

    He's connected a Servo (with separate 5 x 1.5 battery
    , 7.5 volt pack) to a BS2 (with a 9-volt battery).
    The grounds LOOK properly connected -- but that is
    one possible problem -- do you REALLY have a ground
    on the Stamp board?


    Also -- you probably want a 10 uF capacitor between
    the 7.5 volt + and Ground. You should already have
    a 10 uF capacitor on the Stamp side.

    Also -- your diagram shows the yellow wire on the
    far left. Usually, the signal wire is in the middle.
    Are you SURE your BS2 is talking on the signal wire,
    and not the voltage supply wire?



    --- In basicstamps@yahoogroups.com, "Cyrill" <creukelaar@h...> wrote:
    > hallo
    >
    > Take a look at mine servo.doc file in the files directory
    >
    > and please give some help
    >
    >
    >
    >
    > Thanks for any suggestion
    > Cyrill
  • ArchiverArchiver Posts: 46,084
    edited 2004-06-08 12:32
    thanks for the reaction

    What do you mean with really ground ?that the stamp board is connected
    to some kind off mass?Well it isn't.perhaps you wanna explain it some more.
    and why.it should be conneced to really ground.

    >Are you SURE your BS2 is talking on the signal wire,Yes
    I'm sure.

    But it aint possible that the servo uses the current of the 9 volt battery
    ?

    > Also -- you probably want a 10 uF capacitor between
    > the 7.5 volt + and Ground.
    I ll do it.

    cyrill




    Original Message
    From: "Allan Lane" <allan.lane@h...>
    To: <basicstamps@yahoogroups.com>
    Sent: Monday, June 07, 2004 5:43 PM
    Subject: [noparse][[/noparse]basicstamps] Re: servo problem


    > Summary:
    >
    > He's connected a Servo (with separate 5 x 1.5 battery
    > , 7.5 volt pack) to a BS2 (with a 9-volt battery).
    > The grounds LOOK properly connected -- but that is
    > one possible problem -- do you REALLY have a ground
    > on the Stamp board?
    >
    >
    > Also -- you probably want a 10 uF capacitor between
    > the 7.5 volt + and Ground. You should already have
    > a 10 uF capacitor on the Stamp side.
    >
    > Also -- your diagram shows the yellow wire on the
    > far left. Usually, the signal wire is in the middle.
    > Are you SURE your BS2 is talking on the signal wire,
    > and not the voltage supply wire?
    >
    >
    >
    > --- In basicstamps@yahoogroups.com, "Cyrill" <creukelaar@h...> wrote:
    > > hallo
    > >
    > > Take a look at mine servo.doc file in the files directory
    > >
    > > and please give some help
    > >
    > >
    > >
    > >
    > > Thanks for any suggestion
    > > Cyrill
    >
    >
    >
    >
    > 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.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2004-06-08 15:25
    "Really Ground" -- to work with a Servo, you
    MUST have a good common ground between the
    BS2 and the servo voltage supply.

    The pin supplying the 'common ground' from the
    BS2 supply was not clear in your diagram. It
    didn't seem to be connected directly to the
    BS2 power-supply. It seemed to be some distance
    away. So I was not sure that it was even a
    ground pin.

    What happens is, the BS2 drives the signal
    wire with a pulse. The BS2's reference for
    this pulse is the BS2 ground. The Servo's
    reference for reading this pulse is the
    Servo's ground. If both grounds are not
    the same, the pulse looks shifted in voltage
    to the Servo, and won't be read properly.

    If it is read properly, the Servo then uses
    it's Power and Ground wires to actually drive
    the motor inside it. This can again shift the
    ground reference (if both grounds are NOT
    connected properly) leading to 'ghost pulses'
    on the signal wire.


    --- In basicstamps@yahoogroups.com, "Cyrill" <creukelaar@h...> wrote:
    > thanks for the reaction
    >
    > What do you mean with really ground ?that the stamp board is
    connected
    > to some kind off mass?Well it isn't.perhaps you wanna explain it
    some more.
    > and why.it should be conneced to really ground.
    >
    > >Are you SURE your BS2 is talking on the signal wire,Yes
    > I'm sure.
    >
    > But it aint possible that the servo uses the current of the 9 volt
    battery
    > ?
    >
    > > Also -- you probably want a 10 uF capacitor between
    > > the 7.5 volt + and Ground.
    > I ll do it.
    >
    > cyrill
    >
    >
    >
    >
    >
    Original Message
    > From: "Allan Lane" <allan.lane@h...>
    > To: <basicstamps@yahoogroups.com>
    > Sent: Monday, June 07, 2004 5:43 PM
    > Subject: [noparse][[/noparse]basicstamps] Re: servo problem
    >
    >
    > > Summary:
    > >
    > > He's connected a Servo (with separate 5 x 1.5 battery
    > > , 7.5 volt pack) to a BS2 (with a 9-volt battery).
    > > The grounds LOOK properly connected -- but that is
    > > one possible problem -- do you REALLY have a ground
    > > on the Stamp board?
    > >
    > >
    > > Also -- you probably want a 10 uF capacitor between
    > > the 7.5 volt + and Ground. You should already have
    > > a 10 uF capacitor on the Stamp side.
    > >
    > > Also -- your diagram shows the yellow wire on the
    > > far left. Usually, the signal wire is in the middle.
    > > Are you SURE your BS2 is talking on the signal wire,
    > > and not the voltage supply wire?
    > >
    > >
    > >
    > > --- In basicstamps@yahoogroups.com, "Cyrill" <creukelaar@h...>
    wrote:
    > > > hallo
    > > >
    > > > Take a look at mine servo.doc file in the files directory
    > > >
    > > > and please give some help
    > > >
    > > >
    > > >
    > > >
    > > > Thanks for any suggestion
    > > > Cyrill
    > >
    > >
    > >
    > >
    > > 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.
    > >
    > > Yahoo! Groups Links
    > >
    > >
    > >
    > >
    > >
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