garage door PLC ladder diagram

Quick answer：

A PLC ladder diagram is a graphical representation of the control logic used in programmable logic controllers (PLCs). It is used to program PLCs for controlling various automated processes, including garage door openers. The diagram consists of horizontal rungs, or steps, that represent the logic of the control program. Each rung contains contacts and coils that are connected in series or parallel to represent the on/off states of inputs and outputs.