HOA Integer Control from SCADA

Hi all,

I've been asked building a PLC micrologix program for a waste water SCADA system.

We aren't doing the SCADA programming, just the ML 1400.

For control of the dosing pumps they want integer based HOA control.
I can do this using binary and bits but I'm a little torn with the integer based setup.
So basically a number system like 1 Auto, 2= Manual and 3= Off.
I tried doing EQU instructions with an N9 data file if the switch/button on the SCADA HMI choses one of the states but it doesn't seem right. Seems as if I need a 3 option instruction, not just a 2 option which is an EQU.

Any suggestions?

MultiState Push Button with 3 states.


0 = Off
1 = Hand
2 = Auto

Right...
But how would you incorporate those state numbers into control on the ladder...Equ is only giving you two options.

I'm assuming the SCADA system will have a 3 pos button.
Maybe I'm looking too deep

See if the attached screen shot helps.

Yes...that helps.

I was trying to use 3 different integers for source A for each state instead of the one for all 3. This makes sense and it's so simple.

Thx, BOB

You Are Welcome!

A typical HOA manual control forces going through OFF when switching between HAND and AUTO. Do you need that type of operation?

I'm not for sure, Bernie. It doesn't denote that in my instructions, just the purpose of each state. It's controlled by the SCADA with what appears to be a SCADA HOA switch but it doesn't elaborate. It's a pneumatic sandpiper type pump not an actual motor driven pump.

If it does need as Bernie mentioned I "think" you could change to a four state Multistate switch.
0=Hand
1=Off
2=Auto
3=Off


You would just have a parallel EQU of 1 and 3 for off.