Epson RC700, Manual

Page: 277 / 340

4. Troubleshooting (DeviceNet)
RC700 / RC90 Option Fieldbus I/O Rev.14 265
♦
Causes of Error
Possible Cause Examination Method Countermeasure

Disconnected
terminating resistors

Cable disconnection

Disconnected
connector

Disconnected signal
wire
(1) Check that terminating
resistors are connected to
both ends of the network.
(2) Measure resistance
between signal wires with
communications power
supply OFF.
→ Normal: 50 to 70 Ω

Measuring point: Connection
of the trouble unit

For details, refer to the
section
4.1.3.1 Connection
Problem .
Fix the problem.
How to find the trouble
point:
Remove the terminating
resistor on one end of the
network. The trouble point
is where resistance changes
from 120 Ω .

Loose connector

Loose signal wire
Check for the connection of
connectors and signal wires.
→ The connectors and signal
wires should be firmly
connected.

Checkpoint: all nodes and all
branch taps

For details, refer to the
section 4.1.3.2 Loose
Connector and Signal Wire .
Connect the connectors and
signal wires again.

Voltage drop of
communications
power supply
Measure voltage of
communications power supply
at the unit with a trouble.
→ Normal: 11V or more
between V+ and V-

If the voltage is 11 to 14 V,
the unit is a possible cause.
Fix the problem on the unit.
Check the voltage of the
power supply.
Calculate the current
capacity of the cable and add
more communications power
supplies.

Noise
(external cause)
Check the noise intrusion via
the following paths (1) to (3).
(1) Noise via DRAIN (FG)
(2) Induced noise via
communication cable
(3) Communications power
supply
→ For details, refer to the
section 4.1.3.3 Noise
Intrusion .
Take countermeasures
against noise.

Broken unit Replace the broken unit with a
new one.
→ Verify whether the problem
is fixed.
Replace the unit with a new
one.

No cause is
identified.
Identify the trouble point by
dividing the network.
→ For details, refer to the
section
4.1.3.4 Broken Unit
Examination
.