Entering Detection And Existence Detection Circuit 1 - Mitsubishi Electric Melsec-QS Series Safety Application Manual

5
SAFETY APPLICATION CONFIGURATION EXAMPLE

5.6.3 Entering detection and existence detection circuit 1

(1) Application overview
5
5.6 Case Examples
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5.6.3 Entering detection and existence detection circuit 1
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 a laser
scanner. 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 light curtain, laser scanner, and contactors are connected to the 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 laser scanner 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 outputs are turned off when the light curtain signal or laser
scanner signal is turned off or an error is detected in the safety remote I/O
station after the operation is started.
Figure5.18 Entering detection and existence detection circuit
(Partially quoted from "Safety Guide Book - the safety measures of machinery in the workplace"
: Nippon Electric Control Equipment Industries Association.)