Latching Cercuit (Controlling The motor by pressing Start Stop Button)

Latching Circuit for Motor Control – Ladder Logic Application

Objective

To control a motor using momentary Start and Stop pushbuttons. Once the motor is turned ON using the Start button, it should remain energized (latched) even after the Start button is released. The motor should turn OFF only when the Stop button is pressed.

 

Working Principle

• Start Button (I0.0):
  A normally open (N.O.) push-button. When pressed, it energizes the motor.
• Latching Logic:
  The motor output coil (Q0.0) is fed back into the same rung to maintain the ON state, creating a memory or latching loop.
• Stop Button (I0.1):
  A normally closed (N.C.) push-button. When pressed, it breaks the circuit and stops the motor by de-energizing Q0.0.

Ladder Logic Program

 Explanation

• Rung 1 energizes the motor output Q0.0 when all conditions below are true:
• The Start button (I0.0) is pressed.
• The Stop button (I0.1) is NOT pressed (i.e., remains closed).
• The motor output (Q0.0) is used in a parallel branch to maintain the circuit (latching).
• The latching branch ensures that once Q0.0 turns ON, it holds the rung logic true even if the Start button is released.
• Pressing the Stop button opens its normally closed contact, breaking the circuit and turning OFF Q0.0, thereby stopping the motor.