RX300 Expansion Control Unit

RX300 – Expansion Control Unit


The RX300 is an intelligent expansion controller that adds 4 extra sensor input and 4 extra control outputs to any RM210 or RS300 wireless unit. Using RS485 communication, multiple RX300s can be “daisy-chained” on the same wireless unit to provide up to 60 remote sensor inputs and 60 extra control outputs in a wired network up to 1000 feet from the wireless unit. The RX300 controller also incorporates unique circuitry developed in partnership with the Irrometer Company to support the popular Watermark Soil Moisture Sensor. Each RX300 can connect 3 Watermark sensors.

When used for controlling valves, each of the 4 outputs can be configured as either N.O (normally open) or DC latching. N.O. is used to switch existing 24 VAC irrigation currents while DC latching can be used with compatible solenoids to switch valves using the power provided by the RX300 (ultimately from the host RM210 or RS300 unit). Outputs in the N.O. configuration can also be used to switch virtually any other pieces of equipment under low-voltage electrical control, such as pump starting circuits or gate opener input.

When used as a sensor input device the RX300 can be installed close to the sensors sampled – even if 100s of feet removed from host unit. One example would be right above ground level connecting to Watermark sensors. This not only saves greatly on cabling but also increases the accuracy of the measurements since the critical
analog-to-digital conversion is performed in the RX300 while the onwards communication is fully digital.


Sensor ports
Number 4
Excitation voltage 5V DC
ADC resolution 12 bit
Digital counting Always-on or instant frequency
Watermark compatibility Ports 1-3. 100% isolation via relays.
Voltage 7 V DC minimum (provided by host wireless unit)
Consumption Only during sampling, max. 10mA + sensor consumption
Host interface
Compatible hosts Any RM210, RS300 (and legacy RS210 or RS210-CELL)
RS485 option Includes 10ft of RS485 cable with 4pin male Conxall MiniCon connector. Can be extended up to 1000 ft total and multiple RX300 can be daisy-chained using Y-cables
RS232 option Includes 10ft of RS232 cable with 6pin female Conxall MiniCon connector. Can only be extended to approximately 35 feet and cannot be daisy-chained. Typically used where the RS485/SDI12 port on host is used in SDI-12 mode, removing RS485 capability.
Cable Type
Direct Burial no
UV stability high
Color black
Enclosure rating IP65
6.25 x 4 x 3.25 (inches)
Weight 3 lbs


  • RM210 or RS300 host unit

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