Alarm Security System

Alarm Security System

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Heating and Mixing of Products

Automatic Heating and Mixing of Products – PLC Program (S7-1200

Problem Description:

Design an automatic system where two materials are collected into a single tank. Once both materials are present, the system should start mixing and heating simultaneously until the mixture reaches a preset temperature (setpoint). Upon reaching the target temperature, the system should automatically stop heating and mixing.

Develop a Ladder Logic Program for this application using a Siemens S7-1200 PLC.

Diagram:-

Problem Solution

We can solve this problem using a simple and effective PLC logic sequence.

• Two separate level switches are used to detect the presence of Material A and Material B in the tank.

• One empty level switch is used to ensure the tank is ready for the next cycle.

• Single-acting inlet valves (fully open/fully close) are used to control the flow of materials into the tank.

• An agitator motor is used for mixing, mechanically connected to a shaft inside the tank.

• A heater and temperature sensor are installed to heat the mixture.

• Once the mixture reaches the setpoint temperature, the system stops the heater and mixer, and the outlet valve is opened to drain the product.

Process Sequence

1. On pressing the Cycle START button (I0.0) and ensuring the tank is empty (I0.4 ON), the system starts.

2. Inlet Valve 1 (Q0.0) and Inlet Valve 2 (Q0.1) open to fill Material A and B until both level switches (I0.3 and I0.2) are triggered.

3. Once both materials are filled, the inlet valves close, and the agitator motor (Q0.2) and heater (Q0.3) turn ON.

4. The materials are continuously mixed and heated.

5. When the temperature sensor (I0.5) detects the setpoint is reached, the heater and agitator turn OFF.

6. The outlet valve (Q0.4) opens to drain the mixture.

7. After draining is complete and the empty level switch (I0.4) is triggered again, the system is ready for the next cycle.

List of Inputs/Outputs

Inputs

Description	Address
Cycle START	I0.0
Cycle STOP	I0.1
Level Sensor - Material B	I0.2
Level Sensor - Material A	I0.3
Empty Level Switch	I0.4
Temperature Sensor (Setpoint reached)	I0.5

Outputs

Description	Address
Inlet Valve 1	Q0.0
Inlet Valve 2	Q0.1
Agitator Motor	Q0.2
Heater	Q0.3
Outlet Valve	Q0.4

Memory Bit

Purpose	Address
Cycle ON	M0.0

Ladder diagram for automatic heating and mixing of product.

 Network 1:- Cycle ON

Network 2& 3:- Inlet Valve 1 & Heater

Network 4:-Inlet Valve 2

Network 5:-Outlet Valve 

Program Description

In this application, we are using a Siemens S7-1200 PLC with TIA Portal software to program the automatic heating and mixing process.

Network-wise Logic Explanation

Network 1: Cycle ON/OFF Logic

This network implements a simple latching (seal-in) circuit to control the process cycle:

• Normally Open (NO) contact of Cycle START button (I0.0)

• Normally Closed (NC) contact of Cycle STOP button (I0.1)

• Once latched, it activates Memory Bit M0.0 to keep the cycle ON.

• 
  

Network 2: Inlet Valve 1 Control (Material A – Q0.0)

• The Inlet Valve 1 (Q0.0) turns ON when the tank is empty (I0.4 = ON).

• It turns OFF when Material A level is reached (I0.3 = ON).

• The START button (I0.0) is also connected in parallel to allow manual override if required.

• 
  

Network 3: Inlet Valve 2 Control (Material B – Q0.1)

• Inlet Valve 2 (Q0.1) turns ON once Material A level (I0.3) is reached and the Cycle ON (M0.0) is active.

• It allows the addition of Material B after Material A is filled.

• 
  

Network 4: Heater and Agitator Control

• Once both Material A (I0.3) and Material B (I0.2) are at their levels, the Heater (Q0.3) and Agitator Motor (Q0.2) turn ON.

• This continues until the Temperature Setpoint Sensor (I0.5) indicates completion.

• 
  

Network 5: Outlet Valve Control (Q0.4)

• Once temperature setpoint (I0.5) is reached and Cycle ON (M0.0) is active, the Outlet Valve (Q0.4) opens.

• It remains open until the Empty Level Switch (I0.4) detects the tank is empty (used with NC contact to stop the valve).

Note:

This logic is for explanation and conceptual design only. Actual implementation may vary based on sensor types, valve actuation mechanisms, interlocks, and safety requirements.

Runtime Test Cases

Inputs	Outputs	Description
I0.0 = 1	Q0.0 = 1	Cycle started, Inlet Valve 1 ON
I0.4 = 1	Q0.1 = 1	Tank empty, Inlet Valve 2 ON
I0.3 = 1 & I0.2 = 0	Q0.2 = 1	Material A filled, Material B not yet full
I0.2 = 1 & I0.5 = 0	Q0.2 & Q0.3 = 1	Both materials filled, Heating & Mixing ON
I0.5 = 1 & I0.4 = 0	Q0.4 = 1	Setpoint reached, Outlet valve ON