Hi all, I have some doubts that I would like to discuss and I thought that this forum would be the best place - could you contribute with some ideas?
Since I want the device to be as accurate and rugged as possible - I would like to introduce a redundancy for the tilt switch sensor.
The tilt switch sensor has two different uses in this project:
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Wakes up the board (Particle Electron) when the barrier changes state - here I use a filtering, debouncing circuit of my design which you can read more about in the “details” section of this project.
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Is checked by the board for determining the actual state that the board woke up to.
Why redundancy is needed? The Tilt-switch sensor I’m using is an mechnical device - which is good because I can wake up the device this way, and does not consume power when in “open” state. Basically a tube with a steel ball inside - if the ball falls on two contact pins, we have “closed state”, and when you tilt the sensor the ball goes to another end, and we have “open state”. I think that it might be prone to mechanical wear or failure in extreme weather conditions (harsh frost for example?).
QUESTION:
What type of redundancy / double check system would you suggest? I have two ideas which I list below (please comment on these, or/and add your own ideas):
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Second, same type tilt switch sensor (of a different brand for example) with a logic gate, so that even when one gets “stuck” in one state, the other one could work. We could than compare the states in order to check for failure. Still not the best solution since in principle these would be vulnerable to the same type of failure in similar conditions.
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Some other mechanical solution, which is both robust and compact - I suppose such might be available but don’t have anything in particular for now in mind.
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Gyro, accelerometer, IMU or some other type of digital sensor with witch I could check the position after waking up. This gives me some headache since I would like the auxiliary sensor to “take place” of the original one in both tasks and in the same time be as low power as possible. Don’t know is it possible to check the position of these type sensors after deep sleep if the change in orientation happened during deep sleep and it’s stationary again when I check it? Also for power consumption optimization sake, I tend to detach all the sensors form power source when these are not used. I power these - check the state - and cut the power again. Don’t know if this could be used for such sensors. Don’t have much experience with these accel/gyro/9DOF/IMU/MEMS - could you suggest the best one if this approach is of any value?
If you see any flaws in my way of thinking, or have a better idea - please share this in comments section of this project