Analog PID controller on a chip?

I am looking to control the extension of a pneumatic cylinder to a
certain position.

I was hoping to feed the position of the cylinder (through a sensor
such as a pot) back to a simple analog PID controller that would shut
a pneumatic valve on or off depending on where the cylinder is.


In my research I have come across expensive and complicated digital
PID controllers. I have been unable to find a simple analog pid
controller. I could model the system and build my own pid controller
with discrete op-amps and the such, but I need 8 of these controllers
and that approach becomes difficult when multiplied by 8.


Does anyone know if such a product exists, or am I completely off the
deep end with this approach?


Thanks

Ed Lentz
elentz@e...
Tagged:

Comments

  • 6 Comments sorted by Votes Date Added
  • edited September 2000 Posts: 46,084Vote Up0Vote Down
    Hi Ed,

    What you ask is not too difficult. The HVAC industry calls it
    a pilot postioner. These are available in pnuematics for about
    $150.00.

    Electronically, you send a signal of 0-10VDC or 4-20 mADC
    and the on-board circuit changes until the feed-back is of equal
    input value. Typically the feed-back is a load cell and spring, or
    as you mentioned a potentiometer. There are string pull
    potentiometers with a spring return that could be used as the feed-
    back for distance. Alternatively, you could use a linear pot.
    Questions ... How fast is your stroke,
    and how much distance?
    Also, how often is the postion going to change?
    How are you controling the air valves now?

    In addition, if you are driving a shaft that is moving 90° or
    there about, you might be able to use a pot directly linked to the
    shaft.

    Dave


    --- In basicstamps@egroups.com, elentz@e... wrote:
    >
    > I am looking to control the extension of a pneumatic cylinder to a
    > certain position.
    >
    > I was hoping to feed the position of the cylinder (through a sensor
    > such as a pot) back to a simple analog PID controller that would
    shut
    > a pneumatic valve on or off depending on where the cylinder is.
    >
    > In my research I have come across expensive and complicated digital
    > PID controllers. I have been unable to find a simple analog pid
    > controller. I could model the system and build my own pid
    controller
    > with discrete op-amps and the such, but I need 8 of these
    controllers
    > and that approach becomes difficult when multiplied by 8.
    >
    >
    > Does anyone know if such a product exists, or am I completely off
    the
    > deep end with this approach?
    >
    >
    > Thanks
    >
    > Ed Lentz
    > elentz@e...
  • edited September 2000 Posts: 46,084Vote Up0Vote Down
    C'est quoi un PID controller ?


    >From: elentz@e...
    >Reply-To: basicstamps@egroups.com
    >To: basicstamps@egroups.com
    >Subject: [noparse][[/noparse]basicstamps] Analog PID controller on a chip?
    >Date: Thu, 21 Sep 2000 22:36:56 -0000
    >
    >
    >I am looking to control the extension of a pneumatic cylinder to a
    >certain position.
    >
    >I was hoping to feed the position of the cylinder (through a sensor
    >such as a pot) back to a simple analog PID controller that would shut
    >a pneumatic valve on or off depending on where the cylinder is.
    >
    >
    >In my research I have come across expensive and complicated digital
    >PID controllers. I have been unable to find a simple analog pid
    >controller. I could model the system and build my own pid controller
    >with discrete op-amps and the such, but I need 8 of these controllers
    >and that approach becomes difficult when multiplied by 8.
    >
    >
    >Does anyone know if such a product exists, or am I completely off the
    >deep end with this approach?
    >
    >
    >Thanks
    >
    >Ed Lentz
    >elentz@e...
    >
    >
    >
    >

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  • edited September 2000 Posts: 46,084Vote Up0Vote Down
    >
    >In my research I have come across expensive and complicated digital
    >PID controllers. I have been unable to find a simple analog pid
    >controller. I could model the system and build my own pid controller
    >with discrete op-amps and the such, but I need 8 of these controllers
    >and that approach becomes difficult when multiplied by 8.

    Go to Stamps in Class of parallaxinc.com and download the Industrial Control
    manual.
  • edited September 2000 Posts: 46,084Vote Up0Vote Down
    RE: [noparse][[/noparse]basicstamps] Analog PID controller on a chip?

    Hello,

    My name is Nagi Babu. I'm a software consultant living in Minnesota, USA. I'm also a robot hobbyist. I own a www domain that I manage and use to provide free web sites, news groups, etc., to my friends and family members.

    I have participated in this Basic Stamp - message forum for a few months now and have realized that it is way too complicated to follow a conversation thread. For example, when I post a question, I usually care to follow-up on just my conversation thread. I also do care about looking up on the other conversations based on the subject line on the posted message. Since this forum acts like a message board, our mail-boxes fill up fairly quickly - but, most importantly, it gets very difficult to read up on your conversation when those emails flood your in-box - I guess, most of us agree to this.

    Keeping this in mind, I have an idea to create a newsgroup. It will behave just like this forum except, it is far more organized, followable, easy to access, and most importantly, your email box will not be flooded with emails. With a newsgroup concept, you connect to my server using programs such as Outlook Express (or any other news reader program that you might have) and selectively read the message that interest you - and - the converstations that you are participating in.

    Please comment and let me know if you guys will be interested in something like this.

    thanks a lot for your time
    nagi
    nags@crosscity.com
    http://nagi.crosscity.com




    Original Message

    From: carl@gwis.com [noparse][[/noparse]mailto:carl@gwis.com]
    Sent: Friday, September 22, 2000 5:50 AM
    To: basicstamps@egroups.com
    Subject: Re: [noparse][[/noparse]basicstamps] Analog PID controller on a chip?


    >
    >In my research I have come across expensive and complicated digital
    >PID controllers. I have been unable to find a simple analog pid
    >controller. I could model the system and build my own pid controller
    >with discrete op-amps and the such, but I need 8 of these controllers
    >and that approach becomes difficult when multiplied by 8.

    Go to Stamps in Class of parallaxinc.com and download the Industrial Control
    manual.·
  • edited September 2000 Posts: 46,084Vote Up0Vote Down
    Bob Pease (Nat'l Semi) did an analog PID design some years
    ago which IIRC competed with the whiz-bang digital stuff -
    App was controlling the position of a steel ball rolling on
    a track by pivoting the track - Generically the "Ball on a
    beam" balancing problem.

    regards, Jack

    elentz@e... wrote:
    >
    > I am looking to control the extension of a pneumatic cylinder to a
    > certain position.
    >
    > I was hoping to feed the position of the cylinder (through a sensor
    > such as a pot) back to a simple analog PID controller that would shut
    > a pneumatic valve on or off depending on where the cylinder is.
    >
    > In my research I have come across expensive and complicated digital
    > PID controllers. I have been unable to find a simple analog pid
    > controller. I could model the system and build my own pid controller
    > with discrete op-amps and the such, but I need 8 of these controllers
    > and that approach becomes difficult when multiplied by 8.
    >
    > Does anyone know if such a product exists, or am I completely off the
    > deep end with this approach?
    >
    > Thanks
    >
    > Ed Lentz
    > elentz@e...
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