Hi, my name is Annalisa.
I am absolutely new in both coding and forum, so i apology upfront in case this topic is already been discussed.
Here my question, I am thinking to create a kinf od smart dumbbell, or at least this is the idea, using some strain gauges and an accelerometer.
I've read that the best use of strain gauges is configuring them in a wheatston bridge and in the picture attached you can find the configuration I am trying to set.
Attached there is as well the connection of the strain gauges and the acccelerometer like I have imagined they has to be.
My question is, someone can tell me if I am doing this right or wrong?
Thanks for anyone who is gonna help me
The HX711 (not HX771 as in that image) should do the job, but note its normally set up for about 10
reads a second, I think the chip can be configured for 80 reads a second, that might depend on the
exact breakout board used.
The wiring looks plausible, but I've not used the specific modules personally.
OP's image...
"Uniaxial stress". Where is the uniaxial stress in your dumbell? You're using a weight machine and you can put this on the weight carrier?
I just ordered some of these: Biaxial, 90° T Rosette Strain Gauges with Transducer Quality That takes away some of the issues in aligning the two orthogonal strain gauges. I'm going to put one on each side of my uniaxial stress member to eliminate any errors due to unintentional bending.
So, my final idea, but coud be totally wrong, it's just pretty based on intuition, is to have three Wheatstone bridge configurations placed on the dumbell (see picture attached) and then calculate a value that is going to represent the avarage of the three.
Does have any sense?
Anyway my question it was even more basic since i was not even sure that the wiring like I imagined was correct lol, so it will take time probably to reach the step of having the configuration I have in mind tested.
What do you think about the wiring of the Wheatstone bridge like i posted in the picture? Do you think looks ok?
No it doesn't make any sense. Are you trying to measure the bending strain on the bar? Then it's going to depend on how far apart you hold your hands.
Are there any commercial products which do this? Try to work out how they do it.
I would have to brush up on my mechanics but perhaps if the strain gauge was between the hand position and the weights you might get a more precise reading.
However I see three critical areas:
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bonding strain gauges takes some practice, and putting them inside the bar, maybe 1/2 meter from the end will be difficult.
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the readings will be bouncing all around, it may be difficult to get an accurate average. I can't even guess at the required measurement frequency.
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the strain gauges must be oriented on the top or bottom of the bar. When the bar is rotated during the lift, the data will not reflect the true strain.
I would also like to say I appreciate the thought that went into this idea, even if it has issues that stop it from becoming a reality 