How to Allow user to select 2 outputs from HMI but not more!

Btw, if 0-2 pumps are allowed to run and pump 1-4 set bits 0-3 of an INT, then invalid values are either 7 or 11 or >12, so only three tests are required.


also, another approach would be to make the pump 1 start button invisible when

• Pump 1 is on
• OR
• That 4-bit INT is 6 or 10 or 12

So that is only four tests per pump, still brute force but less brutish. Similar logic works for pump 2 (5 or 9 or 12), pump 3 (3 or 9 or 10), and pump 4 (3 or 5 or 6).


N.B. this assumes a jumpered-on pump does not set a bit in that 4-bit INT.

Generalised case in ST:

drbitboy said:

I know you are using CCW, but the principles are the same. KISS. Main(OB1) not shown, but it only calls the pumps' handler FB.


HMI

• Normal operation
  • press up to two [Preset Pump N] buttons to determine which pumps will be on
    • Each [Preset Pump N] button sets one bit in INT PLC INT hmi_pattern.
  • Then press [Send Presets]
    • This will assign a 1 to accept_pattern
    • PLC logic will use hmi_pattern bits determine which pumps to turn off or one, IFF pattern is valid
    • PLC logic will also clear hmi_pattern and accept pattern to 0 to prepare for next set and send.
  • All buttons are "set and forget:"
    • HMI assigns ones (sets)
    • PLC assigns zeros (resets)
• Abnormal operation (shown)
  • Too many pumps are preset
  • Red error message shown
    • Visible when PLC boolean [pattern_valid] is 0
  • Send button is red
    • for the same reason,
    • but it still assigns 1 to accept_pattern,
      • which PLC ignores

View attachment 57466
​

Static array with validity of sixteen possible hmi_pattern values e.g.

• pattern_validities[5] is true, because 5 is 2#0101 => two 1-bits
• pattern_validities[11] is false, because 11 is 2#1011 => three 1-bits
• Changing this to an (Array[0..15] of INT) would enable providing the number of 1-bits, in case the allowable number of pumps changes
  • [0] => 0
  • [1], [2], [4], [8] => 1
  • [7], [11], [13], [14] => 3
  • [15] => 4
  • All others => 2

View attachment 57469
​

Handler for all four pumps

• Determine HMI pattern validity from pattern_validities array
• Handle pump start/stop using pump function
• Delay assigning 0 to accept_pattern bit

View attachment 57467
​

Pump Function

• Seal-in circuit; adding a system Stop bit (not used here) to the main rung on the right would make this a Start/Stop circuit.

View attachment 57468​

Click to expand...

I cannot thank you enough for helping me out.

However, I couldn't find the blocks used in network 2.

What is the function block used as it seems that it is not supported in CCW

L D[AR2 said:

Generalised case in ST:

Click to expand...

Thanks a lot.

I tried using the same text you are using. But I couldn't set the data type to an array as it is not available in CCW. It seems that your are using Siemens PLC which is more capable than what I am using .

ahaanwar2 said:

I cannot thank you enough for helping me out.

However, I couldn't find the blocks used in network 2.

What is the function block used as it seems that it is not supported in CCW

Click to expand...

Ah, the user-defined, one-rung program under [Pump function] is what is used for those blocks.


In CCW I suspect you will have to replace Rung 2* with four duplicates of that [Pump function] rung, and change the hmi_bit and pump_on tags to the specific tags for each pump.


Whether you use the ST or LAD code (and I suggest doing both), please take the time to think them though in your mind, and then test your understanding how they work.


* "Network" is a silly moniker for the rung of a LADDER!

ahaanwar2 said:

Thanks a lot.

I tried using the same text you are using. But I couldn't set the data type to an array as it is not available in CCW. It seems that your are using Siemens PLC which is more capable than what I am using .

Click to expand...

I suspect one issue is the non-literal number of pumps; try using 4 instead of #gc_NumberOfPumps throughout the program and variable declarations.


Another issue might the "of Struct." Instead of Pump.Q, Pump.StartPB, etc., try creating parallel arrays e.g. Boolean Pump_Q, Pump_StartPB, etc.