Hello Folks!
With a friend beekeeper, we started to dig the subject a few yars ago.
Like everybody, we started with the cheapest strain gauge we could find. Stability of the measure was disastrous.
We thought about buying better load cell.
But after research, and discussion with another beekeeper who also searched on the subject, and who has a background in physical measurement, came out of these discussions that there were no good tradeoff between price of the components, and quality (especially stability).
So we moved to a completely different approach, which can be much more DIY-friendly than load cells : we built an automated mechanical scale.
Principle is pretty simple, you take a roman scale, a beam, suspend mass to weigh on one side, slide a counterweight the other side, an articulation between, and that's it. Mass to weigh = ratio of the distance articulation-counterweight / articulation-mass * mass of the counterweight.
Electronically, it becomes very simple, arduino has to drive a stepper motor, and check the status of a sensor (optical, reed..) to detect the balance. No analog layer...
Stability of the measure is dependent on the structural stability of the beam on its length, given there is no constraint on it in the length direction, we could say problem of stability is solved.
The tricky part is now to build something that integrates nicely under a hive.
It's what we worked on.
Quickly, we had prototypes that worked very well.
Then we wanted to make a version that was easy to replicate if we needed to make 10, 20, 30.....
And when we started this "industrialization", we thought about making more and sell it as kit.
Here we are, project is mature enough now :
We release all the sources (mechanic, dedicated board, firmware, cloudware) for DIYers
And for beekeepers who don't have {time/energy/skills} we propose for sale a kit.
If it sounds interesting enough, you may visit our website :
www.openhivescale.org
And the sources :
Cheers, Pierre