12
Andover Controls
Maximum Number of I/O Modules
There is no operational limit to the number of I/O modules connected to the CPU except
the capacity of the power supply. It is possible to insert auxiliary power supplies into the
I/O bus to increase the number of modules supported.
To determine the maximum number of I/O modules your system can support, subtract the
power requirements for each module from the maximum available from your power
supply.
•
PS 120/240 AC 50 U, UPS power supply provides 35 Watts of power
•
PS 120/240 AC 50, non-UPS power supply provides 50 Watts of power
•
PS –48 DC 50, Battery operated power supply provides 50 Watts of power
•
NetController requires 15 Watts of power
Start by subtracting the NetController from the power available from your power supply.
PS 120/240 AC 50 U
35 – 15 = 20 Watts of available power for I/O
PS 120/240 AC 50
50 – 15 = 35 Watts of available power for I/O
PS –48 DC 50
50 – 15 = 35 Watts of available power for I/O
The power requirements for each I/O module is listed in the
Continuum I/O System
Reference Guide
ACC # 30-3001-499 and can be found on individual data sheets.
Maximum Length of I/O Bus
A repeater is necessary if the cable lengths get too long. The following are
recommendations regarding cable lengths for both RS-485 and FTT-10 interfaces:
RS-485 Repeater required if length is >2000 ft. (610 m) or after 32 modules.
FTT-10 Repeater required if length is >8858 ft. (2700 m) bus topology
>1640 ft. (500 m) free topology
Connecting Remote I/O Modules with RS-485
The Continuum system allows I/O modules to be placed in a remote location from the
CPU (NetController). However, long cable lengths can cause signal communications
problems on the Power/I-O bus.
When locating an I/O module remotely it is necessary to add a 120
Ω
terminator to the
bus to compensate for the distance. The terminator must be connected at both ends of
the bus for proper operation.
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