I have AB PLC5/40 CPU and I/O cards - 1771 IFE A and 1771 OFE1 B. Using a DC Current source, I inject say 8mA to the second input channel (2+ , 2- ). At the output card, I put a voltmeter to channel (1+ and 1-).

Can any of you help me what I miss in the steps in writing the Ladder program.

Step1 - Hardware onfigure the cards - input (single ended current) and output(voltage). Step2 - Software configure the cards. Ensure the setting follows the harware setting. After scaling, a ladder with its BTW and BTR is automatically produced by the configuration program.
Step3 - I do not know how to proceed from here.

Do I need to modify the program, etc. If any of you have done this simple simulation, I appreciate very much if you share the full ladder and explain the ladder and also if I miss other steps.

Thank you

 

You need to MOV the data value from the analog input card data table to the output cards data table value .. ie mov n10:2 n11:1

If you copy and pasted the rung data the actual addresses can be given to you

The creation of the BTR/BTW only allows for data flow to and from the modules.. but nothing for the transfer of data to the output module.

Cheers from: Jeremy Pollard, CET The Caring Canuckian! www[.]tsuonline.com http://www.tsuonline.com/

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For the analog input card the BTW (block transfer write) will write configuration information from the processors memory out to the "smart" analog cards brains to tell them their scaling etc. This needs to occur once at start-up or upon a reset etc. You should not fire this instruction endlessly.

Then for the input card the BTR (Block Transfer Read) The processor "reads" the memory inside the analog card and brings it into its memory for usage by the program. Just getting the info and putting it into the processors memory N11 etc. will not do anything to it or with it. You then take that value and use it. A tank level may start a pump when the level exceeds a certain value. If N11:1 is greater than or equal to 75%, start pump and run it until level drops below 50% etc. You must do this with code.

The analog output card you BTW to the card to "assign" the values to be output (usually 0-4095) so you write the output from the processors memory to the "smart" card. The BTR is used only to read back diagnostics etc. (You can actually run without it). So if N12:0 is set to 2047 you have roughly 50% if your scaling is 0-4095 = 100%.

Now if the tank level control a PID, you need to program the PID instruction to get its input from the level memory location you read in and to write to a valve to control level (out N12:0) and the instruction will control the error and the valve manipulation. So when the level goes high (example) the BTR reads this into memory, the PID manipulates based on the setpoint and then your BTW to the analog output will "send" the value out to the card and onto the valve to close or open it depending on the action.

Just configuring the cards will not get any control of them, you must now write the code to transfer info into and out of the processors memory

Short Version.

Dave