Problem Description

Runtime Test Cases
Inputs
Outputs 
Physical Elements
I:1/1 = 1 or I:1/3 = 1
O:2/0 = 1
Open Inlet Valve
I:1/1 = 1 and I:1/2 = 1 O:2/0 = 0
Close Inlet Valve
PLC Program to Control Level of Parallel Tanks
This is a PLC Program to Control Level of Parallel Tanks.

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Problem Description
Two tanks are connected in parallel with a stream line. Heat and Cool the same material and control level
of both tanks. Implement this in PLC using Ladder Diagram programming language.
Problem Diagram
Problem Solution

Heater is used to heat the material and cooling water supply is used to cool down material temperature.

Inlet valve feeds Material to both tanks.

One tank stores material for heating purpose and the other stores material for cooling purpose.

Level switches are used to detect Low level and High level in both the tanks.

Outlet valves are installed in the bottom of both the tanks to drain products for further process.

Mount temperature sensors to measure temperature of both the tanks.

Controlling of these tanks is independent of inlet flow assuming inlet flow to be constant.
PLC Program
Here is PLC program to Control Level of Parallel Tanks, along with program explanation and run time test
cases.
List of Inputs and Outputs
I:1/0
= Start PB
(Input)
I:1/1
= Stop PB
(Input)
I:1/2
= LLST1 Low level of Tank 1
(Input)
I:1/3
= LHST1 High Level of tank 2
(Input)

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 I:1/4
= LLST2 Low level of Tank 2
(Input)
I:1/5
= LHST2 High level of Tank 2
(Input)
B3:0/0 = Latching bit
(Bit)
O:2/0
= V2 To heating tank
(Output)
O:2/1
= V4 outlet from heating tank
(Output)
O:2/2
= V3 To cooling tank
(Output)
O:2/3
= V5 outlet from cooling tank
(Output)
N7:0
= Register to store temperature reading of heating tank
(Register)
N7:1
= Register to store temperature reading of cooling tank
(Register)