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  • Memory Bit

    I am designing a temperature control to turn off an evaporator's fans when the temperature reaches a desired temperature. I need for it turn off and not come back until a differential temperature has been reached. I was told that I could turn off a bit and have it turned back on when the temperature rises to a set differential. My PLC is a DL06 with a FO-04RTD. I would appreciate if someone could direct me to an example on how to do this.
    Thanks in advanced.


  • #2
    If you are familiar with a 3 wire stop/start diagram for a motor control, use the higher temperature (cut out) as a stop, and the lower temperature (Cut in) as the start.
    Essentially, the lower temperature condition starts the fan, is latched on by the fan bit, and stays on until the higher temperature is reached.
    ADEN ENGINEERING
    Automation & Electronic Controls

    Design, Build, Repair, Training

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    • #3
      Here's probably the simplest way of doing this. You may need more complex conditions. The status of the fan itself is the 'memory bit'
      Attached Files
      Last edited by bcarlton; 12-05-2018, 10:39 AM.
      thePLCguy

      Bernie

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      • #4
        Go with Bernie's way. I misread your post and mine works backwards from how I think you want it to.
        ADEN ENGINEERING
        Automation & Electronic Controls

        Design, Build, Repair, Training

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        • #5
          Thanks Guys, I went with Bernie's example. It works great.

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