User's Manual

Page 19
M Series Data Radio – User Manual
© Copyright 2004 Trio DataCom Pty. Ltd.
Part D – System Planning and Design
Power Supply and Environmental
Considerations
General
When mounting the equipment, consideration should be given to the
environmental aspects of the site. The cabinet should be positioned so
that it is shaded from hot afternoon sun, or icy cold wind. Whilst the
radios are designed for harsh temperature extremes, they will give a
longer service life if operated in a more stable temperature
environment. In an industrial environment, the radio modems should
be isolated from excessive vibration, which can cause data errors and
destroy electronic components, solder joints, and crystals.
The cabinet should provide full protection from moisture, dust,
corrosive atmospheres, and residues from ants and small vermin
(which can be corrosive or conductive). The radio modem will radiate
heat from the in-built heatsink, and the higher the transmitter duty
cycle, the more heat will be radiated from the heatsink. Ensure there is
sufficient ventilation in the form of passive or forced air circulation to
ensure that the radio is able to maintain quoted temperature limits.
Power Supply
The power supply should provide a clean, filtered DC source. The
radio modem is designed and calibrated to operate from a 13.8VDC
regulated supply, but will operate from 10-16 volts (filtered) DC.
The power supply must be able to supply sufficient current to provide
clean filtered DC under the full current conditions of the radio modem
(i.e. when transmitting full RF power). See Part I - Specifications for
more details of the power supply requirements.
Solar Applications
In solar or battery-backed installations, a battery management unit
should be fitted to cut off power to the radio when battery levels fall
below the minimum voltage specification of the radio. In solar
applications, a solar regulation unit MUST ALSO be fitted to ensure
that the radio (and battery) is protected from excessive voltage under
full sun conditions.
When calculating solar and battery capacity requirements, the constant
current consumption will be approximately equal to the transmit current
multiplied by the duty cycle of the transmitter, plus the receive current
multiplied by the (remaining) duty cycle of the receiver.
The Tx/Rx duty cycle will be entirely dependent on the amount of data
being transmitted by the radio modem, unless the device has been
configured for continuous transmit, in which case the constant current
consumption will be equal to the transmit current only (at 100% duty
cycle).
Note: Operation below the minimum specified supply voltages could
result in poor radio performance. If the supply voltage falls below
7.2Vdc the radio will shut down. Normal radio startup will not occur
until 10Vdc is supplied.
Site Earthing
The radio must not be allowed to provide a ground path from chassis
to (DB9) signal ground or (-) battery ground. Ensure that the chassis
mounting plate, power supply (-) earth, RTU terminal device, and
lightning arrester, are all securely earthed to a common ground point to
which an earth stake is attached. Please pay particular attention to
24Vdc PLC systems using DC-DC converters to supply 13.8Vdc.
Caution: There is NO internal replaceable fuse, and therefore
the radio modem power supply MUST be externally fused.
(MR450: 3 amp slo-blow fuse, EB450: 5 amp fast-blow fuse,
EH450 Controller: 1 amp fast-blow fuse).