Example of PLC ladder diagram for Filing and Heating Liquid in Tank

In the previous post, I wrote PLC program about Mixing and Heating process. Today, I'm going to write about Filling and Heating process in tank.

It sounds like the same topic in previous post. Actually, it is different. We'll see the sequences and processes. 

Here is the given sequences according to the Author :

1. Fill the tank up to 80%. When the tank is filled, turn ON the heater to raise the temperature up to 70 deg.

2. When this temperature is reached, turn OFF the heater & open the outlet valve.

3. When the level in the tank falls below 10%, close the output valve.

In this situation, I do the ladder diagram via Sysmac Studio which is the product of Omron. I just remind you again, most of the control processes are used with Mitsubishi, Siemen and sometimes Delta's PLC due to cost effectively. I'm going to show you how it works with Sysmac Studio. In this case, I'm only using Name Tags.

Before I'm talking about ladder diagram, I would like to tell about Inputs and Outputs for that.

Input : Level Transmitter, Temperature sensor, Start, Stop, MasterStart, MasterStop.

Output : Inlet Valve, Outlet Valve, Heater.

Let's focus on ladder diagram!

Rung 1 & 6 ( Master Control )

This rung is used with Master Control to control multiple execution of the program. Using is MC and MCR is like nesting the program. When MasterStart is triggered, the program will execute in the nesting program. It will not executed when MasterStop is triggered.

Rung 2 (Inlet Valve)

I am using Latch function by sealing to work Inlet Valve. You can see in the diagram. When the start is triggered, the Inlet_Val is On until Stop, Heater and Outlet_Val is On.

Rung 3 (Water Level)

In here, I used Scaletrans Instruction. According to the instruction, it means that The ScaleTrans instruction converts input values from an input range to an output range. So, the raw data is from 0 to 32767 and  the output range is 0 to 100. I took the output range as Percentage. 

Rung 4 (Heater)

When the level transmitter is reached in 80%, the Inlet Valve is off and the Heater is On.

Rung 5 (Outlet Valve)

When the temperature is reached 70 Degree, the Heater is off and the Outlet  Valve is on until the level in the tank falls below 10%.