Device Lock

Lock

This page is generated from the Unity twin. Published from _docs/context/devices/lock.md — edit it there, not here. Changes made in the wiki are overwritten on the next sync.

A safety door interlock. Holds one or more doors locked, and reports separately whether they are shut and whether they are locked.

Twin device type · twin FB FB_Lock · 6 instances in FG_System · Unity component OC.Interactions.Lock

What it is

A guard door on the cell enclosure with a solenoid interlock: the PLC energises the lock, and the door cannot be opened until it lets go. It is the boundary between an operator and a moving machine.

What the PLC sees

Symbol	Meaning
Control.0	Lock — hold the doors locked
Status.0	Every door it owns is shut
Status.1	Every door it owns is locked

Watch out

Shut and locked are two different facts, and the machine is only safe when both are true. A door can be pushed to and not latched. Treating "shut" as "safe" is a mistake this twin will let you make and the real machine will not forgive. The policy that acts on these bits is in the safety chain.

How the twin models it

One lock can own several doors: the reported bits are "all of them", not "any of them". The doors are real hinged objects and can be dragged open with the mouse while the machine runs, which is how you test what your program does when someone opens a guard mid-cycle.

In this machine

Signal — Two inputs back - closed and locked - and one lock coil out. Secure means BOTH: closed alone is not enough.

There are 6 of them, in FG_System:

Device	Twin PLC path	Group
B_SafetyDoor11	MAIN.FG_System.B_SafetyDoor11	FG_System
B_SafetyDoor12	MAIN.FG_System.B_SafetyDoor12	FG_System
B_SafetyDoor13	MAIN.FG_System.B_SafetyDoor13	FG_System
B_SafetyDoor21	MAIN.FG_System.B_SafetyDoor21	FG_System
B_SafetyDoor22	MAIN.FG_System.B_SafetyDoor22	FG_System
B_SafetyDoor23	MAIN.FG_System.B_SafetyDoor23	FG_System

Control implementations

The twin is master for structure, and that is all this page states. Which control function block each instance becomes, its process-image members and its published HMI struct is the control platform's own knowledge base:

• Beckhoff
• Siemens — no knowledge base published yet