PLC design example Example 1 motor control problem

PLC design example Example 1: motor control problem. Step 1: Requirement analysis: PB 1 (start) PB 2 (stop) M Constraint Additional requirement: momentary pushbutton Function: control the motor

PLC design example ELLD Design of DEC SLLD

PLC design example Requirement analysis: Because PB 1 and PB 2 are momentary pushbutton, we need the latching function. Thus, the modified requirement becomes o FR 1: Latching PB 1. o FR 2: Motor control with latched PB 1 and PB 2.

PLC design example - Design Example 1: motor control problem. Step 2: Concept design or design: PB 1, CRN. O. Latching PB 1 Latched PB 1 (start) CR, CRN. O. PB 2 (stop) M Controlling motor

State variable, input variable, output variable X: State variable: M, CR (CRN. O) Y is part of X, i. e. , I: Input variable: Y=M, which is one of the state variables (M, CR) PB 1, PB 2 Y: Output variable: M

State diagram PB 1 =1 CR N. O. =0 CR N. O. =1 PB 2=1 CR N. O. =1 M =0 M=1 PB 2=1

State equation PB 1 =1 CR N. O. =0 CR N. O. =1 PB 2=1 CR N. O. =1 M=0 M=1 PB 2=1

State equation

State equation

PLC design example

PLC design example

Summary 1. Requirement analysis and its importance. 2. The state equation may further be reduced based on the logical analysis besides based on the logical variable algebra. PB 1 =1 CR N. O. =0 CR N. O. =1 PB 2=1