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The power supply input is nominally rated for 24VDC but can accept a voltage in the range of 10 to
30VDC. The inputs are reverse polarity, surge, overvoltage, and overcurrent protected. The power supply
is not isolated.
MODBUS RTU
These weather stations are equipped with an RS-485 communications port that supports a subset of Modbus
RTU commands. Two baud rates are supported 9600 and 19,200. Only 4X Holding registers are supported.
The register map that follows describes each register. These stations are read-only.
COMMUNICATIONS
Baud: Switch 5 selects the baud rate. ON=19200, OFF=9600 (default).
Data bits: 8
Parity: None
Stop Bits: 1
Maximum Poll Rate: 5 Hz (Extended periods of rapid polling will drain the battery)
SCALING
Parameters are reported as integers. In order to maintain resolution, some values are scaled up. The scale
factor shown indicate how the value should be scaled or multiplied by. Rainfall is an exception, this
parameter reports the number of tips of the tipping bucket rain gauge. Typically the gauge is calibrated to
0.254mm (0.01”) per tip. This counter resets on a reboot and will roll over at 65536 counts.
UNSUPPORTED FIELDS
The register map reserves registers for all combinations of sensors supported by the Rainwise stations. Not
all will be available on any one system. Sensors/fields that are not supported will contain the value 0x8000.
Some fields require the purchase of additional sensors. The values reported by fields that don’t have valid
sensors installed should be ignored.
POWER MANAGEMENT
The weather station will enter a low power mode when the RS-485 bus is quiet. The station will wake on
any activity and will remain awake drawing full power for 3 seconds after the last activity on the bus.
When using the weather station with its own solar power the bus should remain inactive for the majority of
the time. Suggested polling rates are between 1 and 5 minutes. The battery voltage can be monitored to
assess the station health. Readings below 6 volts indicate a low battery. 5.8 volts is considered critical.
If the station is supplied with auxiliary power the above is not applicable and the station can be polled as
often as desired.
In DC powered stations the RS-485 interface board supplies the main board with a regulated 6.8V DC
supply. This is the voltage reported in the Modbus Supply Voltage Modbus register.
