7 Before Starting Positioning Operation
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FX
3U
-20SSC-H Positioning Block User's Manual
7.
Before Starting Positioning Operation
DESIGN PRECAUTIONS
•
Make sure to have the following safety circuits outside of the PLC to ensure safe system operation even during external power supply
problems or PLC failure.
Otherwise, malfunctions may cause serious accidents.
1) Most importantly, have the following: an emergency stop circuit, a protection circuit, an interlock circuit for opposite movements
(such as normal vs. reverse rotation), and an interlock circuit (to prevent damage to the equipment at the upper and lower
positioning limits).
2) Note that when the PLC CPU detects an error, such as a watchdog timer error, during self-diagnosis, all outputs are turned off.
Also, when an error that cannot be detected by the PLC CPU occurs in an input/output control block, output control may be
disabled.
External circuits and mechanisms should be designed to ensure safe machinery operation in such a case.
3) Note that when an error occurs in a relay, triac or transistor output device, the output could be held either on or off.
For output signals that may lead to serious accidents, external circuits and mechanisms should be designed to ensure safe
machinery operation in such a case.
•
At Forward/Reverse rotation limits, make sure to wire the contacts with NC, negative-logic. Wiring contacts with NO, positive-logic
may cause serious accidents.
DESIGN PRECAUTIONS
•
Make sure to observe the following precautions in order to prevent any damage to the machinery or accidents due to abnormal data
written to the PLC under the influence of noise:
1) Do not bundle the main circuit line together with or lay it close to the main circuit, high-voltage line or load line. Otherwise, noise
disturbance and/or surge induction are likely to take place. As a guideline, lay the control line at least 100mm (3.94") or more away
from the main circuit or high-voltage lines.
2) Ground the shield wire or shield of the shielded cable at one point on the PLC. However, do not ground them at the same point as
the high-voltage lines.
•
Install module so that excessive force will not be applied to the built-in programming port, input connectors, power connectors or
optical connectors. Failure to do so may result in wire damage/breakage or PLC failure.
