Electronics > Projects, Designs, and Technical Stuff

Strain gauge Joystick - Could something like this work?

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PeterFW:
I would like a 2 axis input device, i have a few wonky design restrictions i set myself, one is no "moving" parts and so i  came up with the attachment as a rough idea. 

The middle hole is just for attaching the stick of the joy-stick part.
The deflection gets measured with the PCB strain gauges, the cutout makes it more conforming.

I have seen designs like this, so it should work, but what do you think?

amyk:
The whole device becomes the (slightly) moving part!

More seriously,

https://commons.wikimedia.org/wiki/File:Pointing_stick_of_a_Lenovo_ThinkPad_keyboard-4488.jpg

https://commons.wikimedia.org/wiki/File:Pointing_stick_of_a_Lenovo_ThinkPad_keyboard-1047.jpg

george.b:
Aha, I see you've been studying the IBM Trackpoint ;D

That looks like it could work, yes. There has to be a small deflection for it to work, so maybe it's something to keep in mind when it comes to materials/mechanical layout - how much deflection as a result of how much force, and how sensitive a strain gauge you'd have to use.

PeterFW:

--- Quote from: amyk on January 22, 2020, 12:55:18 pm ---The whole device becomes the (slightly) moving part!
More seriously,
https://commons.wikimedia.org/wiki/File:Pointing_stick_of_a_Lenovo_ThinkPad_keyboard-4488.jpg
https://commons.wikimedia.org/wiki/File:Pointing_stick_of_a_Lenovo_ThinkPad_keyboard-1047.jpg

--- End quote ---

Thanks for the reply! 
You are correct, that is why i put the moving in quotation marks :) 

I have read the patent and a few more resources concerning this design, i was just hoping someone maybe has tried it yet and got some practical knowledge. 
Sadly the Trackpoint devices are, as far as i can make out, based on regular FSR. 
I mean, technically a stain gauge is a FSR too but you know what i mean :)

PeterFW:
Thank you for the reply!


--- Quote from: george.b on January 22, 2020, 01:33:27 pm ---That looks like it could work, yes. There has to be a small deflection for it to work, so maybe it's something to keep in mind when it comes to materials/mechanical layout - how much deflection as a result of how much force, and how sensitive a strain gauge you'd have to use.

--- End quote ---

Yea, while i know how strain gauges work and what you have to do to get data from them, i never worked with them. 
On FR4 they should experience a deflection which these usually do not see. 

Maybe i should just design a couple of different arrangements and try them out but i got a problem with resistance. 
Using Copper on FR4 i do not get anywhere near >1Ohm.

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