Timed Single Phase Motor Control

Discussion in 'General Electronics Chat' started by Rising Fawn, Aug 9, 2016.

  1. Rising Fawn

    Thread Starter New Member

    Aug 9, 2016
    3
    0
    Hello.
    I'm new to this forum, and I hope I posted this in the right spot.
    I'm a retired Mechanical Engineer that also ran my own Electrical Contracting Business for many years.

    My brother asked me to help him with a ...what should be....simple control circuit on a 5HP Single Phase Vacuum Cleaner at his car wash.
    Unfortunately, I've been retired for several years, and my memory has faded. What used to be easy has apparently been lost with age.

    The Control that he needs will allow his customers to power the Vacuum Cleaner for 2 minutes by depressing a Momentary Contact Switch.
    At that point, the Vacuum will shut off and cannot be restarted for 2 minutes. At the end of 2 minutes, depressing the start switch will repeat the cycle.
    Using a Single Shot timer and Motor relay, I can easily run the motor for two minutes and have it shut off.
    The problem that I'm having is the time delay circuit to prevent the motor from being restarted until 2 minutes has elapsed.
    As his control is now, the Vacuum motor is turned on and off by a simple 2 position toggle switch, which some of his customer's forget to turn off.
    This leads to the motor running for hours sometimes with no one there.

    Any reply is appreciated
    Thanks
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,541
    2,369
    There is a few ways, what are you using for the one shot timer?, you could run another timer simultaneously for 4 minutes and use it to disable the restart of the 2 min timer.
    555 timers could be used.
    Max.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    If all he's concerned about is the motor being left on, then why does he want a delay before it can be restarted?
     
  4. Rising Fawn

    Thread Starter New Member

    Aug 9, 2016
    3
    0
    I thought that it might require two timers, but I was hoping that it might be more simple than that.
    Thanks
     
  5. Rising Fawn

    Thread Starter New Member

    Aug 9, 2016
    3
    0
    It think that it's to add just a touch of inconvenience to keep any one customer from hogging the vacuum cleaner.
    It they have to wait 2 minuted to turn it on again, more than likely they won't wait. You know how big a hurry people are in now days. He doesn't charge for it, but he doesn't want it running constantly either.
     
  6. avayan

    New Member

    Oct 30, 2015
    12
    2
    Nowadays, projects like these are extremely easy to solve with a microcontroller and a super simple state machine. Now, if you are not into microcontrollers or similar venues, the project remains as hard as it was before. Luckily, there is a gazillion fifth graders (or older individuals) who should be able to program this application using an Arduino like platform in an afternoon!

    The solution to this problem is three loops:

    1. The first loop is waiting for the pressing of a button. When the button press is observed, then the vacuum cleaner is turned ON and you move unto loop #2.
    2. On Loop #2 you wait two minutes. Once the 2 minutes have elapsed, you turn the vacuum cleaner OFF and move to Loop #3.
    3. On Loop #3 you wait two minutes while ignoring the press of the button. Once the two minutes have elapsed, you move to Loop #1.

    Notice this is in essence an "infinite" loop. Wait for the button, wait 2 minutes with the motor ON and then wait 2 minutes with the motor OFF. Repeat, and repeat and repeat... until the sun blows up and consumes the planet or you decide to retire from the car detailing business!

    The beauty about this venue is that it is super easy to change the time as well as the logic. For example, you could change the amount of time you want the unit to be powered ON. Maybe you want it ON for three minutes and then OFF for 1. Whatever it is, it takes seconds to make these modifications!

    It is also quite easy to change the code so that if while the motor is ON the user decides to press the button again, the motor can be turned OFF. So may things that you can do!
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,541
    2,369
    I would have used a 556 for dual timers and a XOR IC for the P.B. for a simple solution.
    Max.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,541
    2,369
    Old post now, but coincidentally I had a similar request come up soon after and solved it with a couple of 555's (or a 556), two 2n7000, a P.B. and a relay.
    Max.
     
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