Sensor battery life and power problem. A 1.5 V battery has a capacity of 600 mAh
ID: 2292619 • Letter: S
Question
Sensor battery life and power problem.
A 1.5 V battery has a capacity of 600 mAh. It will be used in a sensor node with the Zigbee technique employed.
1.) Suppose that the total power used in the sensor node is 3 mW. How long can the battery last?
2.) When the sensor node is in the sleep mode, it will turn off the Zigbee transceiver and save 80% of total power consumption on the sensor. If the node can use sleep mode to keep the transceiver on for only 10% of the time, how long can the battery last?
Explanation / Answer
1)
Given,
For battery: V = 1.5 V
Capacity = 600mAh
Battery Power = Voltage x capacity
= 1.5 x 600 mAh
= 900 mWh
Power used by sensor node = 3mW
Battery time = Battery power/ sensor power
= 900mWh/3mW
= 300h
2) Sensor saves power in sleep mode = 80%
Transceiver on for 10% of time only.
Sensor power uses in sleep mode = 20 % of 3mW
= 0.2 x3 mW
= 0.6 mW
Total power used by sensor = (0.9 x 0.6) + (0.1 x 3)
= 0.54 + 0.3
= 0.84 mW
Battery time = Battery Power / total power used by sensor
= 900mWh/0.84 mW
= 1071.43 h
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