Advertisement
Design Precautions (
Please install a safety circuit to protect the entire control system in case of an unexpected
power shutdown or PLC module malfunction. Such anomalies may severely compromise the
integrity of the overall system.
External to the PLC, please install circuits and switches to safeguard the system from
mechanical damages (ex. emergency stop, upper/lower limit switches, forward/reverse
direction interlocking circuits, etc).
When the PLC detects either of the following failure conditions, it may stop operation and
turn off all outputs.
-
The overcurrent protection or overvoltage protection of the power supply module is
activated.
-
The PLC CPU detected a failure, such as the watchdog timer error or module installation
failure, with its self-diagnostic function.
In addition, all outputs may be turned on when there is a failure that the PLC CPU cannot
detect, such as in the relay or TR terminal. Build an extra monitoring circuit that will monitor
any output signal that could cause serious accidents.
A greater than normal current passed through the PLC for an extended period of time, or a
short-circuited load flowing through the output module may cause a fire.
Build a circuit that turns on the external power supply after the PLC power supply is turned
on. If the external power supply is turned on first, it could result in output failure or
malfunction.
In order to ensure that the system operates safely, please configure an interlock circuit in the
scan program for the following situations:
-
When exchanging data with computer or other devices.
-
When operated by a computer or other devices.
Not doing so could result in output failure or malfunction.
Precautions for design (
Do not bundle the input/output signal or communications cables with the main circuit and
power cables. They should be installed at least more than 100 mm (3.94 inches) apart. Not
doing so could result in output failure or malfunction.
Warning)
Caution)
- 4 -
Advertisement
