WARNINGS
When Designing your GLC System:
- Be sure to design your GLC control system so that in the event of a main power
supply failure or a GLC accident, the user system’s overall safety integrity will be
maintained. If this is not done, incorrect output signals or a GLC malfunction may
cause an accident.
(1) Interlock circuits, etc. designed to interrupt or oppose normal machine movement
(i.e. Emergency Stop, General Protection, forward and reverse rotation, etc.), as
well as those designed to prevent machine damage (i.e. for upper, lower and traverse
movement limit positioning, etc.) should all be designed to be located outside of the
GLC.
(2) Whenever the GLC generates a “Watchdog Timer Error”, GLC operation will halt.
Also, when Errors occur in Input/Output control areas that the GLC cannot detect, it
is possible for unexpected movement to occur in those areas. As a result, for the
purpose of preventing unsafe machine movement, a “Failsafe Circuit” should be
created which is completely external to the GLC.
(3) If an problem arises with an external unit’s relay or transistor, causing an output
(coil) to remain either ON or OFF, a major accident can occur. To prevent this, be
sure to set up external watchdog circuits that will monitor vital output signals.
- Design a circuit that will supply power to the GLC’s I/O unit before starting up the
GLC. If the GLC’s internal program enters RUN mode prior to the I/O unit’s load
control power turning ON, an incorrect output (signal) or malfunction could cause an
accident to occur.
- Design a user program that will ensure the safety of the user’s system, in the event of
a GLC display or control error, or in the event of either a data transmission error or
power failure between the GLC and a connected unit. These types of problems can
lead to an incorrect output (signal) or malfunction, which could thereby cause an
accident to occur.
- Do NOT use GLC touch panel switches to perform life-related or important accident
prevention operations. These operations should be performed by separate hardware
switches to prevent operator injury and machine damage.
Wiring Warnings:
- To prevent electric shock or equipment damage, prior to installing or wiring the GLC,
confirm that the GLC’s power cord is unplugged from the power supply.
- After completing any GLC wiring work, be sure the terminal block’s protective plas-
tic cover is reattached. If this cover is not reattached, an electric shock could easily
occur.
- High voltage runs through the GLC. Except for changing the backlight, do NOT
attempt to open the GLC, since there is a possibility of an electric shock.
- Do not use power levels with the GLC that are outside of the GLC’s specified power
range. Doing so may cause a fire, electric shock or damage the GLC.
- Do not operate or store the GLC in areas where flammable gasses are present, since
operating the GLC may cause an explosion.
DANGERS
