I recently ordered and received a 1kg load cell with the hx711 ADC Module (cheapy from eBay) to possibly use to weigh out small amounts of fish food. But this thing returns very erratic numbers.
I'm using the HX711_ADC library by Olav Kallhovd. I used the included sample sketch to "calibrate" this load cell. And then wrote a sketch that takes measurements over a 2 minute period and stores the highest reading and the lowest reading with no additional weight added.
It reports readings as low as -0.28 all the way up to 1.52. A variation of 1.8 grams. Watching the readings scroll by, I can see it jump from negative numbers to 0.50 (or more) in an instant.
After researching, I am convinced the issue is electrical noise. However, I don't have a way to prove that it is. I read that a 0.1uF capacitor could be placed between the data and clock lines that would help "smooth" the signal. Well, I tried that with a ceramic 0.1uf and get 0s regardless of weight added. Maybe I misunderstood where to place the cap?
I'm looking for a cost effective way to measure amounts of flake in the ballpark of 0.3 to 0.5 grams. But with a swing as wide as this thing reports, it's not possible as it is.
If anyone knows a way to gain much better accuracy/consistency out of one of these cheap load cells, I'm all ears (or eyes as is this case when reading).
Otherwise, does anyone have an opinion on a different approach to weighing small amounts that is in the typical hobbyist's price range?