Sorting Coins with LEGO Bricks and Gravity

LEGO bricks may be toys, but they can also be very useful for constructing rough prototypes. And as LEGO adds more and more bricks to their catalog, the possibilities keep growing. It isn’t uncommon to see makers use LEGO for prototype parts, like enclosures, before they move on to CAD and 3D printing or CNC machining. But even without those extra steps, clever builders can construct useful contraptions from LEGO bricks. YouTuber brickstudios certainly pulled that off with this apparatus that sorts coins with LEGO bricks and gravity.

Like many traditional coin-sorting mechanisms, this relies on the fact that coins come in different sizes. The diameter of a quarter, for example, is much different than the diameter of a penny. In this case, there is a tilted chute with a series of holes — each sized exactly so that only coins of the proper diameter or smaller can fall through. The order of the holes is important: they increase in size. So gravity will send a quarter sliding right past the penny hole and it will continue on until it reaches its hole. A half dollar coin will, in turn, slide past the quarter hole until it reaches its hole.

But there is a complication with US currency: coin sizes do not correspond to their monetary value. For instance, a dime is smaller than both a penny and nickel, despite being worth more. A half dollar coin has a larger diameter than a dollar coin.

For this build, brickstudios didn’t just want to separate the coins, he also wanted to sort them in order of value. That forced him to get creative. Instead of dropping through their holes directly into their respective bins, brickstudios had to send some coins (dimes and half dollars) down winding chutes into bins in the proper order. The complexity of those chutes did result in occasional mishaps with coins getting stuck, but it works pretty well.

Of course, from a practical perspective, this isn’t all that useful. A user flush with change still has to insert each coin into the chute, so they might as well just sort the denominations themselves. Some sort of feed system would make this much more useful and brickstudios had some ideas for that, but chose not to tackle that challenge in this video. If we’re lucky, maybe we’ll get to see an improved version with a feed system in the next video.