Case Examples; Emergency Stop Circuit - Mitsubishi Electric Melsec-QS Series Safety Application Manual

5
SAFETY APPLICATION CONFIGURATION EXAMPLE

5.6 Case Examples

5.6.1 Emergency stop circuit

(1) Application overview
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5.6 Case Examples
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5.6.1 Emergency stop circuit
The emergency stop circuit is the safety application that turns off the power source of
a robot with the emergency stop switch.
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 emergency stop switch and 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) After safety is ensured (Emergency stop signal 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 emergency stop switch
input is turned off or an error is detected in the safety remote I/O station
after the operation is started.
Figure5.5 Emergency stop switch
(Partially quoted from "Safety Guide Book - the safety measures of machinery in the workplace"
: Nippon Electric Control Equipment Industries Association.)