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  1. #1
    Join Date
    Apr 2007
    Location
    Ontario Canada
    Posts
    170

    DX9100 code from simple line code, help

    I know what I want to do, in English it is..

    RWT=Return water temperature
    Output is in milliAmps, an AO on the DX9100

    If RWT is less than 72F
    Then output 7 mA.
    [enables the boilers, which run at their pre-programmed values, proven to work just fine]
    If RWT is greater than 80F
    Then output 4 mA.
    [shuts off the boilers]

    (consequently if the the RWT is between those two limits, after reaching the 80F, output 4 mA which means the glycol boilers are turned off. I may never reach 72F on the RWT till next fall when the heat pumps start putting out more cold glycol on the RWT. The boilers currently run too long and hot and I must impose a 'high limit' of 80F to prevent the cooling tower from running at the same time as the boilers. Don't ask me about retuning the boilers, I've gone as far as I can with the manufacturer and I'm stuck with an 18F start/stop range on them.)

    I have the hardware AO output point configured already, I can pick 0-20 or 4-20 mA.
    I figure two DCO points of 72 and 80F are required.
    I'm struggling with the PM of choice for this situation, and the connections.

    So how do I configure the PMs in a DX9100?
    I can eventually do it with trial and terror, but I'm hoping some of you Johnsons fellows can cut my learning curve down by a lot.
    Thanks

    D'Laine

  2. #2
    Join Date
    Dec 2005
    Location
    San Jose, CA
    Posts
    465
    I've only done a few DX's. I'll try and help...
    If RWT is less than 72F
    Then output 7 mA.
    [enables the boilers, which run at their pre-programmed values, proven to work just fine]
    If RWT is greater than 80F
    Then output 4 mA.
    [shuts off the boilers]
    Use ACO for you're 72 and 80 degrees.EX: ACO1=RW<72 ACO2=RW>80
    Use a comparator to compare AI1 (RW) to ACO1 and set as a low limit. Use the result of the comparator in a PLC to turn on a LRS. then use the LRS into a select block which will output constants to you're AO. One when true and one when false. You're constant will =19% or 7MA. Do the same for youre other logic..

    Like I said its been a while with a DX but this will work..

    Good luck

  3. #3
    Join Date
    Feb 2009
    Location
    Northeast
    Posts
    320
    I would skip the PLC. You can use the two ACO, but it is not necessary. The ACO are useful to map a network controller though. The comparitor has a differential. Either change one of your ACO values to the differential value or use a math pm to subtract the values for the differential. The output of the comparitor is a digital point that you can connect to the forcing input of the analog output. The forcing value I think will need to be a percentage value of the full span. Something like 18.75% should get 7ma on a 4-20ma scale. I think you need a zero value connected to the output source for the off value. I can't remember if the output will limit at 4ma or you need to adjust these values for a 0-20ma span. I am not getting paid for this so I will leave those details to you. The help file has all the info on the pm modules.

    Bill

    PS you may want to use a ON/OFF pm if you want to see some values on the display. The comparitor does not display. Same thing as the Comparitor only more features.

  4. #4
    Join Date
    Jan 2008
    Posts
    51
    dude this is not hard to do but a SOB to explain. I am at the desk today and I will help you through it if you send me your base file. (.dxs)

  5. #5
    Join Date
    Feb 2009
    Location
    Northeast
    Posts
    320
    Quote Originally Posted by prostock View Post
    dude this is not hard to do but a SOB to explain.
    True!

    Bill

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