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Week 10, Power Use Worksheet

The worksheet describing Wordy’s power use is demonstrated in the lecture. Make one for your system (either design or engineering version).

Estimates are ok in place of real numbers. If you have many components, limit it to the top 5-8 most likely to consume power. Even if you have a USB or wall powered system, identify the largest consumers of power and how you might reduce power consumption.

1. What are the different states the device can be in?
The timer can be off, it can actively timing, or it can
be idle (on but not timing).
2. How much will your device be in each state?
It doesn't really seem avoidable to be anything other than "always on" when
actively timing. The LCD is going to be showing the current time remaning
and this will have to updated frequently. Otherwise, it will idle or off.
It can remain in these states for potentially long periods of time. The
Timing states are 5, 15, and 25 minutes long.
3. How much current is used in each state? mA
Active state: -
CPU (100 uA/MHz @ 80 MHz) 8
Accelerometer 0.65
LCD (with backlight) 87
LCD (w/o backlight) 7
4. How long will the device last given a 40mAh battery? Minutes
Backlight on 25
Backlight off 150