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Topic: serious guidance required for a motion sensor (sort of) device (Read 6913 times) previous topic - next topic


I can see you don't want to give the user instant feedback but your unit still needs to watch for and categorize different kinds of movement including twitches? Certainly there needs to be an amount of movement over time to count as a few seconds movement per hour is not enough? If your MCU only looks every 1 second it may miss many small movements by only catching mostly the low switch states or gain a false picture of the opposite. A delay(10) between reads is 10000 microseconds between sub-microsecond digital read. The vibration sensor, what characteristics it has make more difference as you need to read at least twice as fast as it can switch states to not miss data. How much vibration translates to moving a leg far enough to take pressure off veins up at the edge of a chair anyway?

You don't need to reading at microsecond speed and that couples with you don't need to be draining needless power especially if your unit runs on battery. There is a clock divider in the MCU that can be set as high as 256. There is an internal oscillator that runs at 8 MHz, in stand-alone you don't need the crystal or capacitors due to that 'free built-in clock'. The slower your MCU runs the less power it needs in both current and voltage. You could run on a rechargeable watch battery, maybe even an externally powered RFID version.

Other problem is your "mates" who are not friends. Don't tell them all the details. They won't notice. Don't show them your report, or at least not all of it. Those who did not have their hands or heads in the project will become clear enough later unless your prof is a jerk. Just remember that the grade is at best half of what you get while the know-how is what you carry forward for years to come. And don't, whatever you do, don't kiss up to anyone who leaves you out of the good times no matter how they play you.

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

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