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5 SAFETY APPLICATION CONFIGURATION EXAMPLES
5.1 System Configured by a Safety CPU
Case examples
Emergency stop circuit
■Application overview
This safety application cuts off a power to robots using an emergency stop switch. This controls the start and stop of a robot
by turning on or off the main contact of the contractor which opens and closes the power source of a robot at the safety relay
contact.
Connect emergency stop switches and safety relays to safety programmable controllers.
The Safety CPU controls on or off of the safety relays with program.
When the safety programmable controller detects an error with the self-diagnostics, outputs to the safety relays turn off
independent of the program.
In this case, regardless of the program, the outputs remain off until the Safety CPU or safety remote I/O module is reset.
Configure the program so that the following functions can be achieved.
1. Check that safety is ensured (the emergency stop signal is on state). Then, the worker presses the reset switch first.
Pressing the start switch turns on the safety relays.
2. When a safety relay is welded, input the safety relay (normally closed contact) to the safety programmable controller to
prevent starting, and check for welding.
3. To avoid undesired operation of the reset switch and start switch at welding or short-circuit, set the reset switch and start
switch so that they are activated only when turned on and off.
4. Turn off the output of the safety relay, when input of the emergency stop switch is turned off after the operation is started
or an error is detected in a safety remote I/O module.
(Partially quoted from "Safety Guide Book - the safety measures of machinery in the workplace": Nippon Electric Control
Equipment Industries Association)
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