jr0913

RSLogix5 Analog Scaling

5 posts in this topic

Hello there! I am just a few minutes into this and here is my first post. Hopefully this works out! I am very new to Allen Bradley programming.

Anyway, I am trying to replace 4 proximity switches with a laser. The laser needs to be able to tell the RSLogix5 to execute at 4 different positions.

System Information:

  1. RSLogix5
  2. 16 channel analog input card
  3. Input card:  1771-IFE Series C
  4. 4-20 mA signal scaled to 0"-50"

Ive done some digging and cant seem to find a great way to scale an analog signal in RSLogix5.  So far, all Ive come up with is to make 4 different 'LIM' blocks to create a range that matches the existing proximity switches.

Any help is great help! Hopefully I provided enough information. If more is needed please let me know!

 

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Just for clarity for me- is this for a PLC 5? 

 

I can't help with a PLC5 other than help replace it with something from this century :o)

SLC 500 or CLX... no problem

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If you are using the PLC5 you have to scale old school.  Since both of your ranges start at 0 (raw and scaled) then it makes things a little easier.  You can scale at the card level but you lose resolution.  Just use a compute block.  The raw input from an IFE defaults to 0-4095.  0 for 4 ma and 4095 for 20ma.  Hopefully you already have the data transfer from the IFE in the program or it gets a lot harder.  The data from the IFE transfers via a Block Transfer Read (BTR).  You should be able to go into the BTR setup and see the data address associated with your input.  It will be an integer data file such as N7:0.  You can use a compute block (CPT) to do the math.  You will divide your input by 4095 and multiply the result times 50 for your new scale (N7:0/4095*50).  Your destination should go to a floating point such as F8:0.  If your block transfers are not setup then you will probably need to spend some time with the books to get that one figured out. 

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Actually Michael the SLC isn't from this century either!  LOL

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