Epson RC620 Manual page 160

4. Troubleshooting (DeviceNet)
♦ Causes of Error
Possible Cause
 Disconnected
terminating resistors
 Cable disconnection
 Disconnected
connector
 Disconnected signal
wire
 Loose connector
 Loose signal wire
 Voltage drop of
communications
power supply
 Noise
(external cause)
 Broken unit
 No cause is
identified.
150
Examination Method
(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 problem unit
 For details, refer to the section
4.1.3.1 Connection Problem.
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.
Measure voltage of
communications power supply at
the trouble unit.
→ 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 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.
Replace the broken unit with a
new one.
→ Verify whether the problem is
fixed.
Identify the trouble point by
dividing the network.
→ For details, refer to the section
4.1.3.4 Broken Unit
Examination.
Countermeasure
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.
Connect the connectors
and signal wires again.
Check the voltage of the
power supply.
Calculate the current
capacity of the cable and
add more communications
power supplies.
Take countermeasures
against noise.
Replace the unit with a
new one.
RC620 Option Fieldbus I/O Rev.8