Auto and Manual Liquid Tank System: PLC Program Example

Create a PLC program for auto and manual liquid tank system using EcoStruxure Machine Expert-Basic by Schneider Electric.

Contents

PLC Program for Liquid Tank

This article discusses the PLC program for Filling And Emptying tank liquids which can be RUN automatically or manually. When the system is manually operated, the operation of the Liquid Pump, Input Valve, and Output Valve can only be controlled using the Push Button.

When the system runs automatically, if the liquid Tank is empty, the input valve will automatically Open and the liquid pump will Activate 5 seconds later. During the liquid filling process, the Output Valve will always be Closed.

When the liquid Tank is full, the pump input valve will Close and the liquid pump will be Disabled, and the output valve will Open. The liquid pump and input valve will be Active again when the liquid Tank is empty.

Program Explained

Liquid Tank Filling Emptying PLC Program Example

In this program, the system will only RUN if the START_SYSTEM (I0.0) button is pressed and will only STOP if the STOP_SYSTEM (I0.1) button is pressed. By default, the system is in Manual Mode. If the MODE button (I0.2) is pressed then the system Mode will change to Automatic.

In Manual Mode, the PB_PUMP (I0.7) button activates the PUMP Output (Q0.0), the PB_VALVE_IN (I0.5) button activates the VALVE_IN Output (Q0.1), and the PB_VALVE_OUT (I0.6) button activates Output VALVE_OUT (Q0.2).

In Automatic Mode, the system will RUN when the MODE button (I0.2) becomes HIGH/True. In Automatic Mode, the system does not use push buttons to control the PUMP Output (Q0.0), VALVE_IN Output (Q0.1), and VALVE_Out Output (Q0.2). In Automatic Mode, SENS_LOW (I0.3) is used to indicate the lowest point of liquid in the Tank (low level), and SENS_HIGH (I0.4) is used to indicate the highest point of liquid in the Tank (high level).

When the liquid Tank is empty, the NC (Normally Close) SENS_LOW (I0.3) and SENS_HIGH (I0.4) contacts will Activate VALVE_IN (Q0.1) and the PUMP Output (Q0.0) will Activate 5 seconds later to RUN the liquid filling process.

When the Tank is full then the Contact NO (Normally Close) of SENS_LOW (I0.3) and SENS_HIGH (I0.4) will Activate the output VALVE_OUT (Q0.2) to RUN the process of emptying the liquid. VALVE_OUT (Q0.2) will be Closed when the NO (Normally open) contacts of SENS_LOW (I0.3) and SENS_HIGH (I0.4) are LOW/False.

I/O Details

Addressing Input, Output, TIM, Bit Memory, and Word Memory details as follows.

Comment	Input (I)	Output(Q)	Memory Bits
START_SYSTEM	I0.0
STOP_SYSTEM	I0.1
MODE	I0.2
SENS_LOW	I0.3
SENS_HIGH	I0.4
PB_VALVE_IN	I0.5
PB_VALVE_OUT	I0.6
PB_PUMP	I0.7
PUMP		Q0.0
VALVE_IN		Q0.1
VALVE_OUT		Q0.2
SYSTEM_ON			M0
PUMP_1			M1
VALVE_IN_1			M2
VALVE_OUT_1			M3
PUMP_2			M4
VALVE_IN_2			M5
VALVE_OUT_2			M6

PLC Programming Code

The image above shows when the memory Output bit SYSTEM_ON (M0) has been Active. Once the START_SYSTEM (I0.0) push button is pressed then the memory Output bit SYSTEM_ON (M0) becomes Active. Due to the latching, the memory output bit SYSTEM_ON (M0) remains Active even though the START_SYSTEM (I0.0) push button is released.

In Rung-1, (MANUAL NETWORK) you can see that the system can RUN because of the NC (Normally Close) contact from MODE (I0.2).

The image above shows the condition of the output memory bits PUMP_1 (M1), VALVE_IN_1 (M2), and VALVE_OUT_1 (M3) which have been activated manually.

The picture above shows the Output PUMP (Q0.0), VALVE_IN (Q0.1), and VALVE_OUT (Q0.2) which have been Active because the NO (Normally Open) contacts of the memory bits PUMP_1 (M1), VALVE_IN_1 (M2), VALVE_OUT_1 (M3) are in HIGH/True condition.

Liquid Tank Filling and Emptying PLC System

The figure above shows the condition when the system has been RUN in automatic Mode. Because the liquid Tank is empty, the memory Output bit VALVE_IN_2 (M5) becomes Active.

Because the system has been running for more than 5 seconds then the memory Output bit PUMP_2 (M4) becomes Active.

This Step has been going on the process of filling the liquid in the Tank.

Because the NO (Normally Open) contacts of the VALVE_IN_2 (M5) and PUMP_2 (M4) bit memory are Active, the pump (Q0.0) and VALVE_IN (Q0.1) outputs are Active.

The picture above shows the process of emptying the liquid tank. Because the tank is full, the memory Output bit VALVE_OUT_2 (M6) becomes Active. The Interlock function of the VALVE_OUT_2 (M6) bit memory makes the VALVE_IN_2 (M5) and PUMP_2 (M4) bit memory outputs Disabled.