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Expert articles, tutorials, and guides on industrial automation, PLC programming, and HMI design.

Introduction to Human Machine Interface (HMI)

August 28, 2025 7 min read 355 views
In the realm of industrial automation, the Human Machine Interface (HMI) stands as a crucial bridge connecting operators to complex machinery and processes. Understanding the …
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Rung 1 EStop_NC (I0.2): Emergency Stop (Normally Closed) EStop_NC I0.2 Start_Button (I0.0): Start Push Button Start_Button I0.0 Purge_Done (T4.DN): Purge Timer Done Bit Purge_Done T4.DN Burner_Running_Latch (M0.0): Burner Running Latch Burner_Running_Latch M0.0 Pre_Purge_Fan (Q0.0): Pre-purge Fan Pre_Purge_Fan Q0.0 Rung 2 EStop_NC (I0.2): Emergency Stop (Normally Closed) EStop_NC I0.2 Start_Button (I0.0): Start Push Button Start_Button I0.0 Pre_Purge_Fan_Latch (M0.1): Pre-Purge Fan Latch S Pre_Purge_Fan_Latch M0.1 Rung 3 Pre_Purge_Fan_Latch (M0.1): Pre-Purge Fan Latch Pre_Purge_Fan_Latch M0.1 Pre_Purge_Timer (T4): Pre-purge Timer (30 sec) TON Pre_Purge_Timer PRE: T#30s ET: 0ms OFF T4 Pre_Purge_Fan (Q0.0): Pre-purge Fan Pre_Purge_Fan Q0.0 Rung 4 Pre_Purge_Timer.DN (T4.DN): Purge Timer Done Bit Pre_Purge_Timer.DN T4.DN Air_Flow_OK (I0.4): Air Flow OK Air_Flow_OK I0.4 Ignition_Transformer (Q0.2): Ignition Transformer Ignition_Transformer Q0.2 Rung 5 Ignition_Transformer (Q0.2): Ignition Transformer Ignition_Transformer Q0.2 Ignition_Delay_Timer (T0): Ignition Delay Timer (5 sec) TON Ignition_Delay_Timer PRE: T#5s ET: 0ms OFF T0 Rung 6 Ignition_Delay_Timer.DN (T0.DN): Ignition Delay Timer Done Bit Ignition_Delay_Timer.DN T0.DN Fuel_Solenoid_Valve (Q0.1): Fuel Solenoid Valve Fuel_Solenoid_Valve Q0.1 Rung 7 Fuel_Solenoid_Valve (Q0.1): Fuel Solenoid Valve Fuel_Solenoid_Valve Q0.1 Flame_Detection_Timer (T1): Flame Detection Timer (10 sec) TON Flame_Detection_Timer PRE: T#10s ET: 0ms OFF T1 Rung 8 Fuel_Solenoid_Valve (Q0.1): Fuel Solenoid Valve Fuel_Solenoid_Valve Q0.1 Flame_Detector (I0.6): Flame Detector Flame_Detector I0.6 Flame_Detected_Latch (M0.2): Flame Detected Latch S Flame_Detected_Latch M0.2 Rung 9 Flame_Detected_Latch (M0.2): Flame Detected Latch Flame_Detected_Latch M0.2 Ignition_Transformer (Q0.2): Ignition Transformer / Ignition_Transformer Q0.2 Rung 10 Flame_Detected_Latch (M0.2): Flame Detected Latch Flame_Detected_Latch M0.2 Burner_Running_Lamp (Q0.3): Burner Running Lamp Burner_Running_Lamp Q0.3 Burner_Running_Latch (M0.0): Burner Running Latch S Burner_Running_Latch M0.0 Rung 11 Stop_Button (I0.1): Stop Push Button Stop_Button I0.1 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 12 EStop_NC (I0.2): Emergency Stop (Normally Closed) EStop_NC I0.2 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 13 Low_Fuel_Pressure (I0.3): Low Fuel Pressure Low_Fuel_Pressure I0.3 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 14 Air_Flow_OK (I0.4): Air Flow OK Air_Flow_OK I0.4 Flame_Detected_Latch (M0.2): Flame Detected Latch Flame_Detected_Latch M0.2 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 15 Flame_Detector (I0.6): Flame Detector Flame_Detector I0.6 Burner_Running_Latch (M0.0): Burner Running Latch Burner_Running_Latch M0.0 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 16 High_Temperature_Switch (I0.7): High Temperature Switch High_Temperature_Switch I0.7 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0 Rung 17 Shutdown (M1.0): Shutdown Coil Shutdown M1.0 Fuel_Solenoid_Valve (Q0.1): Fuel Solenoid Valve / Fuel_Solenoid_Valve Q0.1 Shutoff_Valve_Close_Command (Q0.5): Shutoff Valve Close Command Shutoff_Valve_Close_Command Q0.5 Alarm_Buzzer (Q0.4): Alarm / Trip Buzzer Alarm_Buzzer Q0.4 Burner_Running_Lamp (Q0.3): Burner Running Lamp / Burner_Running_Lamp Q0.3 Burner_Running_Latch (M0.0): Burner Running Latch R Burner_Running_Latch M0.0 Pre_Purge_Fan_Latch (M0.1): Pre-Purge Fan Latch R Pre_Purge_Fan_Latch M0.1 Flame_Detected_Latch (M0.2): Flame Detected Latch R Flame_Detected_Latch M0.2 Rung 18 T1.DN (T1.DN): 10 Second timer (flame detect) T1.DN T1.DN Flame_Detector (I0.6): Flame Detector Flame_Detector I0.6 Shutdown (M1.0): Shutdown Coil S Shutdown M1.0
Ladder Logic Programs
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Ladder Logic Program for Heater & Furnace Burner Management System (BMS)

August 28, 2025 18 min read 379 views
This ladder logic program is designed for a Burner Management System (BMS) used to safely start, monitor, and stop a gas/oil burner in a process …
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Rung 1 Main_Power_Available (I0.0): Main power available Main_Power_Available I0.0 E_Stop (I0.1): Emergency Stop Button (Normally Closed) E_Stop I0.1 Low_Fuel (I0.2): Low Fuel Level Sensor Low_Fuel I0.2 Low_Oil_Pressure (I0.3): Low Oil Pressure Switch Low_Oil_Pressure I0.3 High_Temperature (I0.4): High Temperature Sensor High_Temperature I0.4 DG_Running (M0.0): DG Running Latch DG_Running M0.0 Fault_Alarm (Q0.3): Fault Alarm Lamp/Buzzer Fault_Alarm Q0.3 Rung 2 Main_Power_Available (I0.0): Main power failure Main_Power_Available I0.0 DG_Stopped_Safely (M0.1): DG has stopped safely DG_Stopped_Safely M0.1 DG_Start_Request (M0.2): Request to start DG S DG_Start_Request M0.2 Rung 3 Manual_Start (I0.5): Manual Start Push Button Manual_Start I0.5 DG_Start_Request (M0.2): Request to start DG S DG_Start_Request M0.2 Rung 4 DG_Start_Request (M0.2): DG Start Request DG_Start_Request M0.2 E_Stop (I0.1): Emergency Stop Button (Normally Closed) E_Stop I0.1 Low_Fuel (I0.2): Low Fuel Level Sensor Low_Fuel I0.2 Low_Oil_Pressure (I0.3): Low Oil Pressure Switch Low_Oil_Pressure I0.3 High_Temperature (I0.4): High Temperature Sensor High_Temperature I0.4 Fuel_Solenoid (Q0.0): Open Fuel Solenoid Fuel_Solenoid Q0.0 Rung 5 Fuel_Solenoid (Q0.0): Fuel Solenoid Enabled Fuel_Solenoid Q0.0 Fuel_Delay (T0): Fuel Delay Before Starter TON Fuel_Delay PRE: T#2s ET: 0ms OFF T0 Rung 6 DG_Start_Request (M0.2): DG Start Request DG_Start_Request M0.2 Fuel_Delay.DN (T0.DN): Fuel Delay Done Fuel_Delay.DN T0.DN Generator_Running_Feedback (I0.7): Generator Running Feedback (Auxiliary Contact) Generator_Running_Feedback I0.7 Starter_Timeout (T1): Starter Motor Timeout TON Starter_Timeout PRE: T#10s ET: 0ms OFF T1 Starter_Motor (Q0.1): Engage Starter Motor Starter_Motor Q0.1 Rung 7 Generator_Running_Feedback (I0.7): Generator Running Feedback (Auxiliary Contact) Generator_Running_Feedback I0.7 DG_Running (M0.0): DG Running Latch S DG_Running M0.0 DG_Start_Request (M0.2): Reset Start Request R DG_Start_Request M0.2 Rung 8 DG_Running (M0.0): DG Running DG_Running M0.0 Generator_ON_Lamp (Q0.2): Generator ON Lamp Generator_ON_Lamp Q0.2 Cooling_Fan (Q0.5): Cooling Fan Cooling_Fan Q0.5 DG_Stopped_Safely (M0.1): DG has stopped safely R DG_Stopped_Safely M0.1 Rung 9 DG_Running (M0.0): DG Running DG_Running M0.0 Changeover_Contactor (Q0.4): Changeover Contactor (DG -> Load) Changeover_Contactor Q0.4 Rung 10 Main_Power_Available (I0.0): Main Power Available Main_Power_Available I0.0 Changeover_Contactor (Q0.4): Changeover Contactor (Main -> Load) / Changeover_Contactor Q0.4 Rung 11 Main_Power_Available (I0.0): Main Power Available Main_Power_Available I0.0 DG_Running (M0.0): DG Running DG_Running M0.0 Cooling_Run_Delay (T2): Cooling Run Delay TON Cooling_Run_Delay PRE: T#30s ET: 0ms OFF T2 Rung 12 Cooling_Run_Delay.DN (T2.DN): Cooling Run Delay Done Cooling_Run_Delay.DN T2.DN DG_Running (M0.0): Stop DG R DG_Running M0.0 DG_Stopped_Safely (M0.1): DG has stopped safely S DG_Stopped_Safely M0.1 Rung 13 Manual_Stop (I0.6): Manual Stop Push Button Manual_Stop I0.6 DG_Running (M0.0): Stop DG R DG_Running M0.0 DG_Stopped_Safely (M0.1): DG has stopped safely S DG_Stopped_Safely M0.1 Fuel_Solenoid (Q0.0): Stop Fuel Supply Fuel_Solenoid Q0.0 Rung 14 Starter_Timeout.DN (T1.DN): Starter Timeout Starter_Timeout.DN T1.DN DG_Start_Request (M0.2): Reset Start Request R DG_Start_Request M0.2 Fault_Alarm (Q0.3): Fault Alarm Lamp/Buzzer Fault_Alarm Q0.3
Ladder Logic Programs
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Ladder Logic Program for Diesel Generator Auto Start/Stop

August 28, 2025 16 min read 331 views
This ladder logic program is designed to control a Diesel Generator (DG) in an automatic power backup system. The primary function is to automatically start …
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Analog vs Digital Inputs and Outputs in PLC Examples & Applications

August 27, 2025 9 min read 493 views
Programmable Logic Controllers (PLCs) are the backbone of modern industrial automation, controlling everything from simple on/off switches to complex robotic systems. Understanding the difference between …
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PLC Arithmetic instructions (ADD, SUB, MUL, DIV with practical examples)

August 26, 2025 8 min read 632 views
Learn PLC arithmetic instructions (ADD, SUB, MUL, DIV) with ladder logic examples for Allen Bradley & Siemens PLCs.
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PLC Retentive Timer Explained with Examples

August 26, 2025 9 min read 844 views
Master PLC Retentive Timers (RTO) with examples, ladder logic, and differences from TON/TOF timers. Learn RTO reset methods.
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