Detcon 880S-N1R - Manual (Page 13)

880-N1R
880-N1R Instruction Manual Rev. 0.0 Page 9 of 38
WARNING: The use of the 880’s 24VDC to power external devices and unit mounted Din-Rail
modules are to be restricted to no more than 3Amps maximum (≈75 Watts). This equates to about 32
sensors, maximum. Care should be taken to insure that the total current load of devices and Din-Rail
mounted modules utilizing this power does not exceed this 3Amp rating, as this may cause detrimental
damage to the unit and will void the warranty. An External Power Source should be used to power
any and all modules or devices that exceed this rating. A 3Amp fuse is installed in the unit to limit the
current load of this 24VDC Output.
A B
RS-485
Primary
A B +
RS-485 VDC
Primary Out
6 7 8 9 10
Part of
TB1
Figure 10 Typical RS-485 connections
Analog Sensor Connections
2. For Analog Units (880A), Sensor communication is accomplished by using Detcon DA4 modules and
the RS-485 Modbus™. The 4-20mA sensors are directly connected to the DA4 modules, while the
DA4 modules are connected via the RS-485 Modbus™ to the 880 PLC (Figure 11). The unit provides
power and Din-Rail space on the back of the unit for a maximum of 5 DA4 modules. Additional DA4
modules should be remotely mounted, require an external power source, and should be connected to
the unit via the RS-485 Modbus™. The correct setup of the DA4’s is covered in Section 4.3 880
Setup.
4-20mA
INPUT
COMM
M
S
D
L
S
D
Typical Sensors
RS-485 to 880
Sensor 2
Sensor 1
Sensor 3
Sensor 4
Figure 11 Typical Analog Sensor Wiring
3. External annunciators should be connected to Detcon RL4 Modules. The Detcon RL4 Modules
communicate via Modbus™, and should be connected along with other serial devices directly to the
RS-485 Modbus™. The correct setup of the RL4’s is covered in Section 4.3 880 Setup. Connections