RSLogix 5 Analog Scaling

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:

RSLogix5
16 channel analog input card
Input card: 1771-IFE Series C
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!

Does the 1771-IFE card already exist with some of the channel already in use?

That card can do the scaling for you although it is common to use the default 0 to 4095 range for the result. You could track down the existing BTW instruction (if card is already in use) and adjust that to 0 to 5000 (inches times 100). Or, you could use a separate scaling instruction to take the raw data from the card and scale it to a floating point result. I usually lean toward having a separate scaling block so that if I need to fine tune the endpoints, I can make that user friendly with whatever HMI or SCADA application might already be in use.

To know for sure what is possible, we may need to know the details of the CPU you are dealing with.

Using the LIM blocks with ranges is the most straightforward way to recreate what you had with discrete proximity switches.

Welcome to the forum....there are still some of us that use the PLC5 regularly....!!

Defo, the 1771-IFE was always quite straightforward for scaling.

Find the Block Transfer instructions, and click on <setup screen> within the instruction, and if someone has done their documentation correct, a pop-up should appear with details of the channel configuration, showing addresses, 4-20mA ranges, scaling - max 0-4095. If not then, the IO configuration table requires to be compiled to get a decent view of the module.

You could multiply the channel address (max 4095) to give 0-5000, or divide to give 0-500 or 0-50, depending on the accuracy you want.

JohnCalderwood said:

there are still some of us that use the PLC5 regularly....!!

Click to expand...

And most wish they wouldn't have to.