Connect with us

IC to protect against voltage faults?

Discussion in 'Electronic Design' started by Mike V., Jun 29, 2004.

Scroll to continue with content
  1. Mike V.

    Mike V. Guest

    I've heard somewhere of a circuit (or IC?) that will turn off your
    voltage source to a motor if the microcontroller that controls the
    system malfunctions (e.g. latches up). If a square wave is not
    continuously applied, then the voltage turns off. For example, in the
    case of a latched-up micro, then the voltage source supplying the
    motor will get switched off. Is there any commercial IC to accomplish
    this? If not, I think it was on Electronics Design magazine, but I
    have no idea which issue it is.
     
  2. The Dallas ds1232(?) comes to mind, but its a reset chip, uc supervisor.
    You can also use a retriggerable one shot (74123) and trigger it via an interrupt routine. This you can set the time-out to your
    liking.

    Cheers
     
  3. Ban

    Ban Guest

    Do you mean a watchdog timer? Google for it, there are hundreds around. It
    will give out a reset signal, which you can route to any convenient points
    in your circuit.
     
  4. Mike V.

    Mike V. Guest

    Martin and Ban, it's not a voltage supervisor nor watchdog that I have
    in mind. I don't want to reset the microcontroller due to a low
    voltage or watchdog timeout. However, I want to do something similiar
    to hardware that controls whether a voltage source to the motor is
    turned on or off. If the micro latches up, and the motor is turned on
    at full speed, then I can cause physical damage with a runaway motor.
     
  5. Joerg

    Joerg Guest

    Hi Mike,

    If this is a cost sensitive application you could do it discrete. Use
    the square wave pulses to keep a capacitor charged which in turn keeps a
    FET conducting. Then when the signal disappears a bleeder resistor (or
    the uC port itself via the charge resistor) discharges the cap and the
    FET turns off. This would not be a very graceful turn-off but it might
    suffice in some applications. Turn on and turn off times can be chosen
    by the respective RC ratios. Sometimes a diode in the charge up path is
    needed depending on the duty cycle of the "uC alive" indicator signal.

    Regards, Joerg
     
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.
Electronics Point Logo
Continue to site
Quote of the day

-