Environmental Engineering Reference
In-Depth Information
TABLE 1.2
Battery Life Estimation for an Xbow Sensor Node Operating at 100% and 1% Duty
Cycles
System Specifications
Currents
Duty Cycles
Value
Units
Model 1
Model 2
Units
Micro Processor (Atmega128L)
Current full operation
8
mA
100
1
%
Current sleep
8
A
0
99
%
Radio
Current in receive
16
mA
75
0.75
%
Current xmit (3dB)
17
mA
25
0.25
%
Current sleep
1
A
0
99
%
Logger
Write
15
mA
0
0
%
Read
4
mA
0
0
%
Sleep
2
A
100
100
%
Sensor Board
Current (full operation)
5
mA
100
1
%
Current sleep
5
A
0
99
%
Computed Average Current Consumed (mA)
Model 1
Model 2
uP 8.0000 0.0879
Radio 16.2500 0.1635
Flash Memory 0.0020 0.0020
Sensor Board 5.0000 0.0550
Total current (ma) used
29.2520 0.3084
Source
:C ossbow Technology Inc., “MPR-MIB Users Manual,” Crossbow Resources, Revision
A, 2007 [21].
the high power consumption of the sensor node for a long period of time.
Based on an AA alkaline battery of 3000 mA-hr, it is illustrated in
Figure 1.11
that the lifetime of the battery powering the sensor node is computed to last
at most 1.1 years. After which, without battery replacement, the sensor node
can be considered an expired node. This is even worse for the case of a coin-
type 250-mA-hr alkaline battery, which is smaller in size than the AA battery.
Referring to
Figure 1.11
, the coin battery can only sustain the operation of the
sensor node for at most 1 to 2 months. Clearly, a lifetime of a year or so or
even less for the wireless sensor node to operate is far from sufficient because
the duration of the node's operation could last for several years for the WSN
to be useful in practical situations. This is a serious limitation to computing
paradigms like ubiquitous computing or sensor networks, in which there
are dozens or hundreds of small self-autonomous sensor node systems with
batteries to maintain.
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