Door Lock Circuit - Mitsubishi Electric Melsec-QS Series Safety Application Manual

5
SAFETY APPLICATION CONFIGURATION EXAMPLE

5.6.2 Door lock circuit

(1) Application overview
5
5.6 Case Examples
- 14
5.6.2 Door lock circuit
The door lock circuit is the application that keeps the door closed until the power
source of a robot stops with the spring lock type safety switch attached to the door of
the safety barrier.
The safety switch is normally locked by spring power. When voltage is applied to the
solenoid, the lock is released and the door can be opened. Specifically, the lock is
released with the status signal, indicating such as the stop status of a robot.
The robot cannot be started during unlocking or opening the door.
The application controls the start and stop of a robot by turning on or off the main
contact of the contactor which opens and closes the power source of a robot at the
safety relay contact.
The safety switches and the safety relays are connected to the safety PLC.
The safety PLC controls the ON/OFF status of the safety relays with a sequence
program.
When the safety PLC detects an error using the self-diagnostics, the outputs to the
safety relays are turned off independent of the sequence program.
When the outputs are turned off with the self-diagnostics, the OFF status is
maintained regardless of the sequence program until the safety CPU module or safety
remote I/O module is reset.
The following functions are realized with the sequence program.
1) When the safety switch is on, pushing the reset switch, then the start
switch turning the safety relays on.
2) When the safety relays are welding, input the close contacts of the safety
relays to the safety PLC for avoiding the start, and check for welding.
3) The reset switch and start switch are set to start only when changed from
ON to OFF for avoiding an accidental start of the switches at welding or
short-circuit.
4) The safety relay outputs are turned off when the stop switch is pressed.
5) The safety relay outputs are turned off when an error is detected in the
safety remote I/O station after the operation is started.
Figure5.11 Door lock circuit
(Partially quoted from "Safety Guide Book - the safety measures of machinery in the workplace"
: Nippon Electric Control Equipment Industries Association.)