Entering Detection And Existence Detection Circuit 2 - Mitsubishi Electric Melsec-QS Series Safety Application Manual

5
SAFETY APPLICATION CONFIGURATION EXAMPLE

5.6.4 Entering detection and existence detection circuit 2

(1) Application overview
5
5.6 Case Examples
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5.6.4 Entering detection and existence detection circuit 2
The entering detection and existence detection circuit is the safety application that
detects the entrance and existence of a human in a hazardous area and turns off the
power source of a robot.
The entrance of human to the hazardous area is detected with a light shielding of the
light curtain. The existence of human in the hazardous area is detected with mat
switch. When the entrance or existence of human has been detected, a robot is
stopped.
The robot cannot be started until the human leaves the hazardous area.
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.
The safety PLC controls ON/OFF status of the contactors with a sequence program.
The light curtain and the contactors are connected to the safety PLC.
The relay is connected between the mat switch and safety PLC.
The safety PLC controls ON/OFF status of the contactors with a sequence program.
When the safety PLC detects an error using the self-diagnostics, the outputs to the
contactors 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 (The light curtain and mat switch signals are both
on), pushing the reset button, then the start button turning the contactor
on.
2) When the contactors 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 contactor output is turned off when the light curtain signal or the relay
input of mat switch is turned off or an error is detected in the safety remote
I/O station after the start.
Figure5.25 Entering detection and existence detection
(Partially quoted from "Safety Guide Book - the safety measures of machinery in the workplace"
: Nippon Electric Control Equipment Industries Association.)