My project is a weighing machine that fills Blueberries into punnets.
The blueberries pour into a hopper that is weighed by a Micro Load Cell ( 5kg RB-PHI-118).
The Load Cell is hooked up to an Arduino Uno with a Wheatstone Amp shield. ( RB-Onl-38)
Once the target weight is reached the Arduino commands to a servo that opens a gate that drops the Blueberries into a punnet. End Loop.
My problem is the Load Cell readings fluctuate wildly. Even with no weight.
I read the previous forum string about a similar problem using a different amplifying shield, that suggested that the interference might be caused by peripheral components, in my case, the servo.
I removed the servo and this was indeed the culprit. Most ( but not all) fluctuations disappeared.
How can I solve this problem?
I attach a copy of my sketch and apparatus.
Load cells and Wheatstone bridge circuits need accurate references to work correctly. Our hobby grade modules are just not up to it. Industrial grade ones would have accurate references that use bandgap, have thermal compensation and other circuitry that make them accurate. I would not use these hobby circuitry for commercial use. Can you accept 10% (or more drift) over time?
Use a HX711 load cell amplifier , which has its own reference circuitry and digital output , and also drive the servo from a separate power supply - the UNO shouldn’t be used to drive such a heavy load , it also creates a lot of electrical noise .
Should then work fine . Not sure how it stacks up with any weights and measure authority, but that’s a different issue !
Wolframore - . No, 10% drift would not be acceptable. Would need to re-set it at intervals. Any idea where to start looking for proper Ind. grade Load cells? Appreciate your advice.
