Ryan Bates makes extraordinary kits for arcade cabinets as well as other related accessories. The problem with this is that in doing so he has to count out a lot of nuts. So much so in fact that he decided it was worth it to make a machine that does this task for him.
What he came up with is an Arduino-powered device that rotates nuts on a spinning platter into a slide fixture that separates them. The idea is based off of a pill counting machine, and different nuts can be counted by adjusting the position of the separation fixture. With the nuts properly spaced, they can be counted using an induction — or prox — sensor, giving quite good accuracy, especially when running larger components.
A master Arduino is used to count the parts, index the cups that they drop into, and control the main platter servo indirectly via a relay. A slave Arduino takes care of actually driving the main platter when the relay is engaged.
Watching this, you may wonder why he didn’t just buy a machine or use a fulfillment house. The answer, of course, is a limited budget, and that just spending money would make a much less interesting YouTube video. This, of course, isn’t his first try at a counting machine, you can find his first attempt here.