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Controller
Hardware and Accessories Setup and Utility
Control System for Remote Devices Via a Single Three-wire Cable
General Description
Galileo Controllers, with the addition of RTU (Remote Terminal Unit) adapter, enables
users to control a system of remote terminal units that are interconnected via a single
three-wire cable. The C2000-15 adapter is a standard module inserted into one of the
controller slots and then defined accordingly. This adapter uses 2 wires to supply the power
required to operate the remote units, and the third wire is used for two-way communication.
Communication also utilizes the - wire (-) as reference for the signals.
The cable remote unit (appears in illustrations as RTU) is intended, first and foremost,
for operating hydraulic valves, but also for reading inputs, such as water meters, fertilizer
meters and pressure stats. Outputs are operated using the pulse (latching) method, and
they can be used to operate other devices in addition to irrigation valves, such as fertilizer
devices, pumps, main Valves, etc., all according to controller definitions.
Following are the types of existing remote units:
Product Name Outputs Discrete Inputs Analog Inputs P/N
CRTU 2-2 2 2 None AMRC0F02
CRTU 4-8-4 4 8 4 AMRC0F04
This type of cable, which is laid over long distances, is by its very nature a source for
numerous types of electromagnetic interference, such as lightning and static electricity.
Therefore, in the product itself and in the order of installation, special attention is paid to
grounding and lightning protection devices. A protection device of the controller’s adapter
card is a separate device that is called LP1, and is installed next to the controller. This
device must be well grounded.
Block diagram of the linear remote unit system:
The system is operated by a 24 V direct current (DC). The maximum output that a single
adapter card can tolerate is 20 Watt. Each unit, when it is inactive, consumes 0.02 Watt
(without analog inputs). Activation of an output, whether for closing or opening, causes
discharging of the capacitor, which is later recharged for 10 seconds. When the capacitor
is charged, the capacity of the unit increases to approximately 1 Watt. Each remote unit
Appendix 1: Cable Remote Terminal Units (CRTU)
Galileo 2000 Controller
Power Supply
module
Adapter C2000-15
Main EMD-03
Lightning
Protection
Device -LP1
RTU 1 RTU 2 RTU 3
Three wire cable for
communication and
power supply