I use counting scales for this purpose. This started when selling Lego bricks in bulk, the weight of the bricks is amazingly constant so I'd just toss 10 bricks on the scales after zeroing it and then it would be pretty accurate up to a 1,000 bricks or so. Add another 2% to account for damage or discoloration and it worked just fine, not a single complaint about quantity or quality.
I want an open-source screw identification / sorting machine.<p>I dump in a bunch of screws and bolts, and I know which are M4 x 3mm, which are 1/4" wood screws, etc.
This reminds me:<p>I can't stand the fact that screws and nails are measured by the pound (at least in the US). What a ridiculous unit of measure to use for a count of something. I have never, not once, thought to myself "I need 2 pounds of nails for this job" because only a lunatic would think of "how many" in terms of weight.
No description of operation or assembly instructions or anything. The readme says 'some upgrades are needed'.<p>If I wanted a screw counting machine I would think about building this, but since I don't at the moment, I would like to know how it works.<p>If you are just curious about its operation, then I think you may be disappointed.