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I hope to use a piezoelectric button to harvest and produce a sufficient energy burst to power ON and bootup a MSP430 for a few ms enough to update a simple data structure (e.g. two integers stored in nonvolatile memory e.g. FRAM) and then power OFF. Note that the MCU will be completely dead before the piezo button press. This updated data structure will be used later on when sufficient energy is available to do more complex tasks (e.g. perform computation/send signal over wifi etc.).

Assume: The FRAM-range MSP430 (e.g. MSP430FR59xx) with lowest clock frequency (32kHz), min. operational voltage 1.8V, lowest power mode that can do the above operation. I'm not sure how much current the above operation (integer updating) would require, but I assume it's under 0.5mA, lasting for under 10ms. Assume there is another solar energy harvesting element that is charging up a secondary energy buffer (e.g. a largish capacitor) to do the complex MCU actions mentioned above.

I guess the objective is to see if there is a way to capture user input in a quick and dirty fashion and react upon the input later, when sufficient energy is available from the secondary energy source.

Questions:

  1. Can a piezoelectric sensor button or a capacitive touch sensor button produce enough energy to perform the above?

  2. Assuming (1) is possible and there are 2 such buttons (A and B), then can the MCU obtain knowledge of which button was pressed and gave it power?

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    \$\begingroup\$ @RonBeyer It seems pretty clear that Rosh wants to power it from the button. \$\endgroup\$ – user253751 May 2 '19 at 3:02
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    \$\begingroup\$ @RonBeyer That's what they are asking. If the only thing it does is powers on, increases a counter by one and then turns off, would a piezo crystal or other energy harvesting method be enough? If you have some evidence that its not, then you should put that in an answer. \$\endgroup\$ – Passerby May 2 '19 at 3:36
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    \$\begingroup\$ @Bimpelrekkie - I understand that it is trivial to power a MCU using a solar panel and rechargeable battery, but i'm interested in a battery-less design. Not looking to replace existing solutions, but simply exploring options. \$\endgroup\$ – bd3lk May 2 '19 at 8:33
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    \$\begingroup\$ How much work are you willing to require the user to do? I can imagine an industrial-size pushbutton that requires 1 N of force and 1 cm of travel to activate. That's 10 mJ of work on the part of the user. If you can capture 10% of that energy (spin a small PM generator?), that's 1 mJ, or maybe 1 mA @ 2V for 0.5 s, which should be more than enough to do what you've outlined. \$\endgroup\$ – Dave Tweed May 2 '19 at 12:23
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    \$\begingroup\$ @Rosh There is a magnetic module produced by Enocean: farnell.com/datasheets/… \$\endgroup\$ – Jack Creasey May 2 '19 at 15:06