User's Manual

Page 20
E Series Data Radio – User Manual
© Copyright 2005 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 destroy electronic components, 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 Section L
- 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 readily serviceable internal fuse,
and therefore the radio modem MUST be externally fused
with a fuse and fuse holder (ER450: 3 amp fast-blow fuse,
EB450: 5 amp fast-blow fuse).