Panasonic FP3 Technical Manual page 43

J Sefety
In certain applications, malfunction may occur for the following reasons.
Power on timing differences between the FP3 or FP10S system and I/O or motorized devices.
An operation time lag when a momentary power drop occurs.
Abnormality in the FP3 or FP10S, power supply circuit, or other devices.
In order to prevent malfunction from resulting in system shutdown, the following special attention is required.
Start up sequence:
The FP3 and FP10S should be operated after all of the outside devices are energized. To keep this sequence, the
following measures are recommended.
- Set the mode selector switches from PROG. mode to RUN mode after power is supplied to all of the outside
devices.
- Program the FP3 and FP10S so as to disregard the inputs and outputs until the outside devices are energized.
Emergency stop circuit:
Add an emergency stop circuit to controlled devices in order to prevent a system shutdown or an irreparable
accident when malfunction occurs.
Interlock circuit:
When two motions that are opposed to each other are controlled, add an interlock circuit between the
programmable controller's outputs and the control device.
Example:
When a motor clockwise/counter-clockwise operation is controlled, provide an interlock circuit
that prevents clockwise and counter-clockwise signals from inputting into the
motor at the same time.
Using alarm output of power supply unit:
The ALARM output goes ON when the watchdog timer is
activated by a program error (eg., infinite loop) or an error in the
hardware itself. The ALARM output terminal has two relay
contacts, N.O. and N.C. on the power supply unit, which can be used as external alarm signals. The watchdog
timer is a program error and hardware error detection timer. It goes ON when the scandal time exceeds 640 ms.
When the watchdog timer is activated, at the same time the ALARM LED lights, the ALARM contacts on the
power supply unit go ON, all outputs to the output units are turned OFF and the unit is put in halted state.
(The system is in a non-processing state that includes communications with programming tools as well.)
J Grounding
The frame ground terminal (FG) is internally connected to the metallic part of the backplane, and used for the earth
grounding.
The line ground terminal (LG) is the midpoint terminal for the internal noise filter.
When the effects of noise are large, ground as shown in diagram below.
The LG terminal has an electric potential so be sure to ground it to prevent electric shock when connecting with the FG.
LG
FG
Use electric wires that are thicker than 2 mm
Make the ground point as close as possible to the programmable controller, and make the length of the ground wire short.
Use a dedicated ground. If the ground is shared with other devices, a reverse effect may occur.
Programmble
controller
LG
FG
2
and with less than 100
Other device
such as
an invertor
Power supply
Alarm signal
(lamp, etc.)
LG
FG
grounding resistance.
Other device
Programmble
such as
controller
an invertor
3-2. Wiring
Power
supply unit
COM
ALARM
NO
37