harvesting power from typing motion using pzt and magnet

[jeromekang]

the setup is to be placed in a wireless computer keyboard..

the project would make use of piezo and the principle of magnet inductance in a keypress...

the problem is that even from walking, the harvested power is low even more from just typing...

what parameters should we concern ourselves in choosing the right components for the ac to dc converter (rectifier), dc to dc step up and then to the supercapacitor to lessen the losses or improve the efficiency per power transfer? Any suggestions for the dc to dc step up? im confused with this part of the circuit as to why it is needed.

 

[dick_freebird]

I'd say to start with the fundamental problem that fingers on
keyboard supply not enough power to be useful, and look
elsewhere for an input source?

Not all energy is worth the effort and materials it takes to
harvest it. That's a lesson in itself, although it might not please
whoever set you upon this path.

There a lot of energy harvesting schemes out there and very
few good opportunities, in terms of watts per dollar.

You could begin by determining how many joules per keypress
in mechanical form would be tolerated by the user, how many
keystrokes per use-interval and how much power or total energy
you are required to supply meanwhile. If this does not make
thermodynamic sense, you can quit before you spend any
more time and money. Unless you really need that "A".

 

[jeromekang]

yeah i wish we could have chosen a different device for using piezo transducers but we have to finish this project. This is more of a proof of concept kind of project and maybe we aren't able to show that we could prolong the onboard battery by 20%(an objective) but we still have to show it through experimentation.

 

[studystudystudy]

jeromekang, i also using the piezoelectric energy harvesting as my project.

maybe we can share experience with each other.

there are some IC for energy harvesting,very good IC
https://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1799,P90393

the dc to dc step up you may used is Boost converter. but it have a problem where you need mosfet or any transistor as a switch.
https://en.wikipedia.org/wiki/Boost_converter

nice to meet you, hope we can share experience together

 

[jeromekang]

@studystudystudy

thanks for those links. yeah i've seen that IC before and was actually planning to buy it but the packaging made me hesitate. I want to test the system first in a breadboard. Will I be able to? And with the boost converter, yes it will be a problem if the switch is a transistor as it will i think not suitable for very very low power applications.

 

[FvM]

but we still have to show it through experimentation

But it can save you a lot of time to estimate expectable results before. I followed dick_freebirds suggestions and calculated a mechanical energy < 1mWs for a typical keyboard click. It's most likely difficult to "harvest" more then a few percent of this energy. You should know better how far you can get with this energy amount in your project.

 

[Mr.Cool]

hey, great idea! but if this means that i have to press the keys harder due to b-emf or otherwise then forget it.

Mr.Cool