Problem Description

Problem Diagram

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Problem Solution

Use limit switches, control valves and motor agitators separately for all three mixing tanks.

The only common input to all these tanks is Material feeding by two valves.

Use separate timers for each tank for mixing.

First two tanks are tagged as primary mixing tanks and the third one is said to be secondary mixing tank.

Use switches of stop buttons of both Primary mixing processes as an input to start the tank third to enter into
the process sequence.
PLC Program

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Here is PLC program to Control Three Mixing Devices in a Processing Line, along with program
explanation and run time test cases.
List of Inputs and Outputs
I:1/14
= Start 
(Input)
I:1/15
= Stop
(Input)
O:2/15
= Master Coil
(Output)
I:1/0, I:1/5, I:1/7
= Level of Material B Switches
(Input)
I:1/1, I:1/4, I:1/8
= Level of Material A switches
(Input)
I:1/2, I:1/3, I:1/6
= Low Level Switch (empty tank)
(Input)
O:2/0, O:2/4, O:2/8
= Inlet Valves to feed Material A (Output)
O:2/1, O:2/5, O:2/10
= Inlet Valves to feed Material B (Output)
O:2/2, O:2/6, O:2/9
= Agitator Motors M1, M2 and M3
(Output)
O:2/3, O:2/7, O:2/11
= Outlet Valves for product outlet
(Output)
T4:0, T4:1, T4:2
= Timers to mix materials
(Timer)

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Ladder
 
Diagram
 
for
 
Mixing
 
Tank
 
1

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