User`s guide

Appendix A - Logic Application Examples

Basic Start/Stop Circuit Example

Release E UMC800 Control Builder User’s Guide 229

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Basic Start/Stop Circuit Example

Basic Start/Stop Circuit

PB1 PB 2

Motor

Start Stop

The basic PLC start/stop circuit may be used to start a process,

turn on motors, etc. With PB2 normally wired as a normally

closed STOP pushbutton (but shown as a normally open

contact in PLC ladder logic), an activation of the PB1

pushbutton turns on 1M (Motor 1). The motor starter switch 1M

contact is detected ON in the next scan cycle, latching the

startup circuit. Depression of PB2 opens circuit, causing Stop.

Equivalent Boolean Logic and Expression

UMC 800 Logic

The UMC solution could use a latch block (4 blocks total)

with no motor switch contact feedback or logic blocks as

shown incorporating motor switch contact (6 blocks total).

A = PB1, B = 1M

D = Output

(A + B) * C = D

C = PB2,

AND

PLC Ladder logic