Instruction manual

9522B Iridium Satellite Modem
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25
Power Calculation
Note: When configuring a power supply (i.e. solar panel and battery) for
a remote station it essential to design with the worst case scenario
in mind. This will help to ensure that the station will perform as
expected.
The power calculation for data transfer can be carried out now
that the transfer time is known. The modem has the following
power consumption characteristics:
- 0 mA when powered off
- 300 mA stand-by
- 800 mA transmit (2500mA max)
The time slot for powering the modem must be long enough to
allow for the complete downloading of the datalogger’s data.
Refer to Table 2 or make your own calculation based on the
collection interval you intend to use.
It is advisable to make the time slot longer than the minimum
download time required to allow for initial connection times and
possible retries. It is also advisable to arrange the time slot
during a time of day when the power supply is its most robust.
For a solar powered station this would be the early afternoon.
The periods of power consumption in a day can be divided up as
follows:
Period A: the modem is powered off – 0 mA
Period B: the modem powered up in stand-by mode –300mA
Period C: the modem is transmitting the data – 2500mA
Now consider a 35 Kbyte data file size and a datalogger
programmed power time slot of 1 hour; the Periods above
become:
Period A = 24 hours - Period B – Period C
Period B = 30 minutes – Period C
Period C = 30 Seconds (from Table 2)
We can substitute in the Period B and C values to obtain all
Periods:
Period A = 23 hours = 0.0 Ah/Day
Period B = 29.5 minutes @ 130 mA = 0.1475 Ah/Day
Period C = 30 Seconds @2500mA = 0.0208 Ah/Day
The total draw for the data transfer is the sum of the periods,
0.1683 Ah/Day, one day per week.
Note: The Ah/Day value is obtained by multiplying the minutes in the
Period by the current draw in Amperes and dividing the product by
60.