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P w m

ArchiverArchiver Posts: 46,084
edited 2004-06-01 19:18 in General Discussion
Hi everyone,

is that possible to do a kind a PWM with a 555 controled by a BS2 is
anyone did before. I want to do a motor speed controler.

Regards

Chris

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2004-06-01 17:45
    It might be fun to find out. Connect the 555 as a VCO and use the PWM
    filtered PWM output to control it.

    -- Jon Williams
    -- Applications Engineer, Parallax
    -- Dallas Office

    Original Message
    From: vermettechristian [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=izD--Gk2DjPenLyX9mTsdX0aWUGsrpkCPktXpk223sQw6BUlwkt4fR_M7pTUIuAUokJ5tIx1evYIj6n4QeSYU14zeGSYKA]christian_vermette@v...[/url
    Sent: Tuesday, June 01, 2004 11:32 AM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] P W M


    Hi everyone,

    is that possible to do a kind a PWM with a 555 controled by a BS2 is
    anyone did before. I want to do a motor speed controler.

    Regards

    Chris
  • ArchiverArchiver Posts: 46,084
    edited 2004-06-01 18:35
    --- In basicstamps@yahoogroups.com, "vermettechristian"
    <christian_vermette@v...> wrote:
    > Hi everyone,
    >
    > is that possible to do a kind a PWM with a 555 controled by a BS2 is
    > anyone did before. I want to do a motor speed controler.
    >
    > Regards
    >
    > Chris


    What benifit would you get with a 555 ?

    It seems the PWM in not a perfect duty cycle, but makes the full count
    come out right over time. For motor control, the more accurate the
    pulse stream the higher efficency you will get in the motor.

    I may have answered my own question. you send a varying signal to
    the 555 instead of a pot and that will adjust the more accurate 555
    duty cycle....

    Dave
  • ArchiverArchiver Posts: 46,084
    edited 2004-06-01 19:18
    >--- In basicstamps@yahoogroups.com, "vermettechristian"
    ><christian_vermette@v...> wrote:
    > > Hi everyone,
    > >
    > > is that possible to do a kind a PWM with a 555 controled by a BS2 is
    > > anyone did before. I want to do a motor speed controler.
    > >
    > > Regards
    > >
    > > Chris
    >
    >
    >What benifit would you get with a 555 ?
    >
    >It seems the PWM in not a perfect duty cycle, but makes the full count
    >come out right over time. For motor control, the more accurate the
    >pulse stream the higher efficency you will get in the motor.
    >
    >I may have answered my own question. you send a varying signal to
    >the 555 instead of a pot and that will adjust the more accurate 555
    >duty cycle....
    >
    >Dave


    I was going to suggest a method that involves using two Op-Amps.
    One generating a triangle wave, and the other acting as a comparator.
    The Triangle wave feeds one leg of the comparator, while the other
    leg of the comparator is fed PWM from the stamp. The Output of the
    comparator is a 0% to 100% duty cycle.

    When searching for a relatively simple circuit to generate a triangle
    wave from an Op-Amp, I came across these excellent article which basically
    describe what I had in mind...

    http://www.cpemma.co.uk/throbber.html
    http://www.cpemma.co.uk/pwm.html#classic

    ... have fun!


    >
    Beau Schwabe Mask Designer II National Semiconductor Corporation
    500 Pinnacle Court, Suite 525
    Mail Stop GA1
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