5 installation precautions, 5 installation precautions -13 – Proface LT3300 - 5.7 All-in-One HMI" User Manual
Page 80
Chapter 4 Installation and Wiring
4-13
4.2.5
Installation Precautions
External power failure or failure of the LT unit may cause abnormal behavior.
To prevent such abnormal behavior from leading to the abnormal operation of the entire system, and to ensure
fail-safe operation, configure circuits which may lead to machine damage or accident due to abnormal
operation (emergency stop circuit, protection circuit, interlock circuit, etc.) externally to the LT.
This section describes examples of the system circuit design to improve system reliability and to ensure
optimum performance.
Fail-safe Design of the Electric Circuit
Design the electric circuit with consideration to equipment malfunctions caused when the LT is turned on by
a delay among the startup times of the control equipment connected to the LT output unit (especially the one
operated by a DC power supply), the LT unit itself, and the program. When remote I/O is used, create a
program that checks the status of the terminal with a logic program.
For example, connect voltage relay coils to the power supply circuit of the LT output unit and the power
supply circuit of the connected control equipment, and connect the contact to the LT input unit. Configure the
circuit to check the ON signal from the voltage relay in the logic program before executing the ladder of the
control equipment connected to the LT output unit.
Rated Voltage
Be sure to supply an appropriate power supply voltage to your LT that is within the specified range.
Power-down
LT unit enters power-down status when an instantaneous power interruption of the rated voltage continues for
10ms or longer.
When the LT unit enters power-down status, it stops the calculation even if the instruction is not finished.
For example, when the LT unit enters power-down status while 100 words of data are being transferred by an
FMOV instruction, the transfer stops midway.
Consequently, design your program with consideration to power-down occurrences.