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Old December 14th, 2017, 12:44 PM   #1
mcmenomy8
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Celsius to Fahrenheit

I'm using a Mitsubishi PLC with GT Designer3 and GX Works 3 and I am trying to create a switch that will change my numerical display between celsius and fahrenheit. I'm a beginner at this and am having troubling figuring out how this is done. Please help.
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Old December 14th, 2017, 12:50 PM   #2
alive15
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Create two rungs in your logic. One rung has your switch "on" input. The 2nd rung has your switch "off" input. Have two outputs created that display Celsius and Fahrenheit. Put one output on each rung to be displayed.
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Old December 14th, 2017, 01:40 PM   #3
boneless
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Quick tip. Remember that there is a different scaling for absolute setpoints and relative setpoints.

If you use hysteresis or deadbands in your program, remember to scale these accordingly .

Yes I know this by experience
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Old December 14th, 2017, 01:40 PM   #4
mcmenomy8
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So, where do I program in the equation that will make the numerical display switch?
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Old December 14th, 2017, 01:42 PM   #5
AndOsk
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Mitsubishi PLC

First you will need to know the input from the tempsensor. is it using a INT as input amount. In wich range can the sensor go from. You will need to define what type of sensor it is. When you know what the values mean then you can try and convert them to either Celcius or Fahrenheit.
Post me if you need any more help.
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Old December 14th, 2017, 02:48 PM   #6
janner_10
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Stick to whatever your used to in PLC calcs (I assume it's F if you're from USA) and just display something different on the screen with a C / F button.
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Old December 14th, 2017, 06:55 PM   #7
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Have a button for C and a button for F. If they hit the F button, tell them no, either passive aggressively or with a popup that explains the benefits of standardisation.
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Old December 15th, 2017, 02:52 AM   #8
janner_10
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Quote:
Originally Posted by AustralIan View Post
Have a button for C and a button for F. If they hit the F button, tell them no, either passive aggressively or with a popup that explains the benefits of standardisation.
Or just a pop up which says 'It's not 1950!"
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Old December 15th, 2017, 03:06 AM   #9
Ronnie Sullivan
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He's a beginner folks.

In the PLC program, you have to get the value from your temperature probe and convert that to either F or C.
You then have to use an equation ie MUL D100 K9 D101 DIV D101 K5 D102 etc to change it to the other.

You will then have both values in 2 separate registers

How you display these on the HMI is up to you
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Old December 15th, 2017, 10:03 AM   #10
mcmenomy8
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Thanks guys, I got it figured out. My customer wants to be able to display Fahrenheit. Celsius would be just fine with me. But I have to do what the customer is paying for. So thank for the help.
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Old December 15th, 2017, 10:22 AM   #11
alive15
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Set the HMI with two push buttons, one Celsius and one Fahrenheit, place the HMI on a pool table, and hire Ronnie Sullivan to select whichever button you want by hitting the cue ball into the button.

May want to have a couple HMIs on hand for back-up in case the first one breaks.
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