Shop OBEX P1 Docs P2 Docs Learn Events
DC motor speed control signal — Parallax Forums

DC motor speed control signal

ArchiverArchiver Posts: 46,084
edited 2001-02-28 04:33 in General Discussion
I need a tachometer signal to time slow rotations (10-80 deg/sec) of a
4-inch drum driven by a DC motor. Is it realistic to try to print an
alternating black/white stripe sequence on a laser printer, tape it around
the drum, and then to "watch" this sequence with a source/receiver
photodiode to generate a square wave tachometer signal? If so, would
printing on white paper be OK, or is another surface better?

Thanks,
Dennis

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2001-02-26 05:26
    Good method, works pretty good especially for slow signals. I've used IR
    reflective photosensors at about 3/4 inch and had good results. The ones
    I've used have the emitter and sensor mounted at "an optimal angle" in a
    plastic body with a mounting slot. I think Digikey has these for a buck
    or two each.

    On Sun, 25 Feb 2001 20:49:46 -0800 "Dennis P. O'Leary"
    <doleary@h...> writes:
    > I need a tachometer signal to time slow rotations (10-80 deg/sec) of
    > a
    > 4-inch drum driven by a DC motor. Is it realistic to try to print an
    > alternating black/white stripe sequence on a laser printer, tape it
    > around
    > the drum, and then to "watch" this sequence with a source/receiver
    > photodiode to generate a square wave tachometer signal? If so,
    > would
    > printing on white paper be OK, or is another surface better?
    >
    > Thanks,
    > Dennis
    >
    >
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >

    ________________________________________________________________
    GET INTERNET ACCESS FROM JUNO!
    Juno offers FREE or PREMIUM Internet access for less!
    Join Juno today! For your FREE software, visit:
    http://dl.www.juno.com/get/tagj.
  • ArchiverArchiver Posts: 46,084
    edited 2001-02-26 18:05
    >I need a tachometer signal to time slow rotations (10-80 deg/sec) of a
    >4-inch drum driven by a DC motor. Is it realistic to try to print an
    >alternating black/white stripe sequence on a laser printer, tape it around
    >the drum, and then to "watch" this sequence with a source/receiver
    >photodiode to generate a square wave tachometer signal? If so, would
    >printing on white paper be OK, or is another surface better?
    >
    >Thanks,
    >Dennis


    Hi Dennis,
    A laminated plastic film _might_ be better from the standpoint of
    dimensional stability and water/oil resistance. For inkjet
    printing, I swear by the white opaque polyester film from Luminos:
    http://www.lumijet.com/Lumijet.htm


    best regards,
    -- Tracy
  • ArchiverArchiver Posts: 46,084
    edited 2001-02-26 18:45
    Another solution is to use a pair of hall effect sensors with a
    couple magnets glued to the inside or outside of the drum. You'll
    want to get a PAK-VII from http://www.al-williams.com/awce/ so you
    can count the two channels at once. You could count rotations with a
    single sensor, but for RPM's, two would be best mounted 90 degrees
    apart and measure the time between them.

    Hope this helps...

    - Brice

    > >I need a tachometer signal to time slow rotations (10-80 deg/sec)
    of a
    > >4-inch drum driven by a DC motor. Is it realistic to try to print
    an
    > >alternating black/white stripe sequence on a laser printer, tape
    it around
    > >the drum, and then to "watch" this sequence with a source/receiver
    > >photodiode to generate a square wave tachometer signal? If so,
    would
    > >printing on white paper be OK, or is another surface better?
    > >
    > >Thanks,
    > >Dennis
    >
    >
    > Hi Dennis,
    > A laminated plastic film _might_ be better from the standpoint of
    > dimensional stability and water/oil resistance. For inkjet
    > printing, I swear by the white opaque polyester film from Luminos:
    > http://www.lumijet.com/Lumijet.htm
    >
    >
    > best regards,
    > -- Tracy
    >
    >
    >
    >
    > Your use of Yahoo! Groups is subject to
    http://docs.yahoo.com/info/terms/
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2001-02-28 02:08
    Thanks to Tracy, Orrin and Brice for good suggestions. Because my drum
    problem requires such slow rotations, less than 1/4 revolution per second,
    I'm trying a really simple approach -- operating "open loop" without a tach
    signal. I'm using a 12 V geared, DC reversible motor from Jameco which
    requires only 45 mA at no load. I need 4 constant velocities, selectable by
    4 pins on a Stamp, so the plan is to use 4 open-collector channels of a
    ULN2003 driver chip, each with a different valued 1% current-limiting
    resistor in series with the motor's ground. The resistor values will
    determine the speed to an accuracy of about 1%, and a regulated 12 V supply
    will keep everything more or less stable, at least in theory. This does
    require 4 stamp pins, each selecting a motor speed, but simplifies
    programming and parts count.

    I though this approach might also be useful for some slow 'Bot applications,
    like arm or head movements.

    Dennis
    Original Message
    From: Orrin f Drew [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZH8fjfwf1s1lr4FaBcDfwypT4CwOnbJ3oxJWA612IagqDEVnujLh-ZczjLxAx6aUlZqu8HYZ6A]odrew@j...[/url
    Sent: Sunday, February 25, 2001 9:27 PM
    To: basicstamps@yahoogroups.com
    Subject: Re: [noparse][[/noparse]basicstamps] DC motor speed control signal


    Good method, works pretty good especially for slow signals. I've used IR
    reflective photosensors at about 3/4 inch and had good results. The ones
    I've used have the emitter and sensor mounted at "an optimal angle" in a
    plastic body with a mounting slot. I think Digikey has these for a buck
    or two each.

    On Sun, 25 Feb 2001 20:49:46 -0800 "Dennis P. O'Leary"
    <doleary@h...> writes:
    > I need a tachometer signal to time slow rotations (10-80 deg/sec) of
    > a
    > 4-inch drum driven by a DC motor. Is it realistic to try to print an
    > alternating black/white stripe sequence on a laser printer, tape it
    > around
    > the drum, and then to "watch" this sequence with a source/receiver
    > photodiode to generate a square wave tachometer signal? If so,
    > would
    > printing on white paper be OK, or is another surface better?
    >
    > Thanks,
    > Dennis
    >
    >
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >

    ________________________________________________________________
    GET INTERNET ACCESS FROM JUNO!
    Juno offers FREE or PREMIUM Internet access for less!
    Join Juno today! For your FREE software, visit:
    http://dl.www.juno.com/get/tagj.



    Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
  • ArchiverArchiver Posts: 46,084
    edited 2001-02-28 04:33
    Why not use a binary decoder and just three pins? 000 = off, 001-100 = 4
    speeds.
    Original Message

    > Thanks to Tracy, Orrin and Brice for good suggestions. Because my drum
    > problem requires such slow rotations, less than 1/4 revolution per second,
    > I'm trying a really simple approach -- operating "open loop" without a
    tach
    > signal. I'm using a 12 V geared, DC reversible motor from Jameco which
    > requires only 45 mA at no load. I need 4 constant velocities, selectable
    by
    > 4 pins on a Stamp, so the plan is to use 4 open-collector channels of a
    > ULN2003 driver chip, each with a different valued 1% current-limiting
    > resistor in series with the motor's ground. The resistor values will
    > determine the speed to an accuracy of about 1%, and a regulated 12 V
    supply
    > will keep everything more or less stable, at least in theory. This does
    > require 4 stamp pins, each selecting a motor speed, but simplifies
    > programming and parts count.
    >
    > I though this approach might also be useful for some slow 'Bot
    applications,
    > like arm or head movements.
    >
    > Dennis
    >
    >
    Original Message
    > From: Orrin f Drew [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=qIp3hyRoUgPFJf5BL94W8KVUJ1LeGc_VBndSmybdeXVHtrO4VN0ZjOnIj4_EFqi49q_2qQ]odrew@j...[/url
    > Sent: Sunday, February 25, 2001 9:27 PM
    > To: basicstamps@yahoogroups.com
    > Subject: Re: [noparse][[/noparse]basicstamps] DC motor speed control signal
    >
    >
    > Good method, works pretty good especially for slow signals. I've used IR
    > reflective photosensors at about 3/4 inch and had good results. The ones
    > I've used have the emitter and sensor mounted at "an optimal angle" in a
    > plastic body with a mounting slot. I think Digikey has these for a buck
    > or two each.
    >
    > On Sun, 25 Feb 2001 20:49:46 -0800 "Dennis P. O'Leary"
    > <doleary@h...> writes:
    > > I need a tachometer signal to time slow rotations (10-80 deg/sec) of
    > > a
    > > 4-inch drum driven by a DC motor. Is it realistic to try to print an
    > > alternating black/white stripe sequence on a laser printer, tape it
    > > around
    > > the drum, and then to "watch" this sequence with a source/receiver
    > > photodiode to generate a square wave tachometer signal? If so,
    > > would
    > > printing on white paper be OK, or is another surface better?
    > >
    > > Thanks,
    > > Dennis
    > >
    > >
    > >
    > >
    > > Your use of Yahoo! Groups is subject to
    > > http://docs.yahoo.com/info/terms/
    > >
    > >
    >
    > ________________________________________________________________
    > GET INTERNET ACCESS FROM JUNO!
    > Juno offers FREE or PREMIUM Internet access for less!
    > Join Juno today! For your FREE software, visit:
    > http://dl.www.juno.com/get/tagj.
    >
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
    >
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
    >
Sign In or Register to comment.