Connect with us

A Discriminating Circuit?

Discussion in 'Electronic Basics' started by Randy Gross, Nov 29, 2003.

Scroll to continue with content
  1. Randy Gross

    Randy Gross Guest

    Greetings,

    I am searching for a circuit that either senses the rectified feed to a
    12vdc motor, or its speed, and, if the voltage, or speed, falls below a
    preset, then it either trips a breaker else energizes a relay that will
    supply an alternative (a battery to boost rpms).

    Here's the catch. That same circuit would have to sense that the motor feed
    has regained the correct voltage and disengage the booster.

    A good analogy here would be a motor driving an alternator. When the motors
    speed drops below that necessary to maintain the desired output, because
    the primary (rectified 12vdc) feed has been interrupted, the feed is
    disengaged and an alternative feed (battery) is engaged until the primary
    feed has regained, at which time the secondary feed is disengaged and the
    primary resumes.

    This is an experiment and the process is trail and error. I know very
    little about digital circuitry and this system needs that kind of
    precision.

    an Inquiring mind,
    Randy Gross
     
  2. usually, a current measurement is used as a means to determine an
    overload condition, since torque is roughly proportional to current.
    A suggestion: Think instead, in terms of continuous regulation of the
    input voltage via some switching regulator with continuous feedback of
    the generator speed (frequency). A PID controller (proportional,
    integral, derivative) that compares the measured speed (frequency) to
    a fixed setpoint. You tune the gain coefficients on the three terms
    to get the best response to changing conditions. The PID controller
    can be made with one or three opamps and the ones in many voltage
    regulator PWM control chips might well fill the bill. Keeping all
    this decision making in the analog realm makes things work smoother.
    The over current limit works just like an over current override on a
    regulated supply.
     
  3. Randy Gross

    Randy Gross Guest

    <>...
    : Randy Gross wrote:
    <Snip>
    :
    : > Here's the catch. That same circuit would have to sense that the motor
    feed
    : > has regained the correct voltage and disengage the booster.
    :
    : A suggestion: Think instead, in terms of continuous regulation of

    You're right! Continuous regulation makes more sense than the intermittent
    approach I described. Maintaining the correct frequency is my main concern.
    My programming professor had a term she tried to hammer into our skulls
    everyday, and that term was K.I.S.S.

    K eep I t S imple S tupid,

    sometimes I forget;-)


    Thanks John

    the
    : input voltage via some switching regulator with continuous feedback of
    : the generator speed (frequency). A PID controller (proportional,
    : integral, derivative) that compares the measured speed (frequency) to
    : a fixed setpoint. You tune the gain coefficients on the three terms
    : to get the best response to changing conditions. The PID controller
    : can be made with one or three opamps and the ones in many voltage
    : regulator PWM control chips might well fill the bill. Keeping all
    : this decision making in the analog realm makes things work smoother.
    : The over current limit works just like an over current override on a
    : regulated supply.
    :
    :
    : --
    : John Popelish
    :
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
Loading...
Electronics Point Logo
Continue to site
Quote of the day

-