I'd like to learn more about mechanical contraptions. It's a good opportunity to help A+ learn about them too if she wants. We've made cardboard automata, dispensers, and conveyor belts. LEGO is so much easier to work with because the pieces are all standardized and they work together smoothly. We like building a variety of candy dispensing machines around Halloween, because we get a lot of differently-shaped candies in little packages. We also have a lot of off-brand balls for LEGO Great Ball Contraptions (there's another fun rabbithole there), so that's always something that can be dispensed.

Olivia's Cupcake Cafe 41366 has a tiny little cupcake vending machine that demonstrates the core concept of filling a reservoir and then moving a slider back and forth to let one object drop. It's a nice little build without any Technic pieces, so you can probably make it with whatever bricks, tiles, and plates you have around.

There are also tons of unofficial builds for dispensers and vending machines. I haven't tried all of the ones below, but they might give you a sense of the different kinds of things people like to do. It's hard to wade through all the minute variations in the search results looking for things that use interesting mechanisms, so I've indexed a few to help people figure out input/mechanism/output variations.

The thing with video tutorials, though, is that they're hard for A+ to independently go through. They're hard for me to go through. I have to keep pausing, rewinding, and finding the different pieces. We don't like getting interrupted by ads, either. It's much easier to have LEGO-style step-by-step PDF instructions on a tablet screen.

I spent part of a day figuring out a simple ball dispenser using Bricklink Studio. This works with the LEGO soccer balls or basketballs that are used in Great Ball Contraptions. You can push/pull the slider to move one ball from the top opening under the reservoir to the bottom opening above the tunnel. It's pretty flexible - you can substitute other bricks/plates/tiles as needed. Here's a render of what it looks like:

The core of it is a slider that accepts a ball from the reservoir and moves it backwards so that it drops down the hole near a slope that sends it rolling to the front. When the slider is pushed towards the back, part of the slider blocks the hole under the reservoir so that balls do not fall through until the slider returns to the front.

To adapt this design to objects of other sizes or shapes, you might want to start by building the slider around the object you want to dispense, and then building the rest of the dispenser to fit it. If the object rolls, you can use this slider design to push it to the back and have it roll to the front. If the object doesn't roll, you can flip the design so that the reservoir is near the back and the output hole is near the front, like the build in Olivia's Cupcake Cafe. The design in the instructions blocks only half of the opening because that's enough to stop the ball from going through, but you can also build a slider that completely blocks the opening if you have something more granular or more tippy.

In the spirit of free/libre/open source software, here are both the PDF instructions and the Bricklink Studio source file under the CC0 public domain license. Feel free to do whatever you want with it: remix, reshare, whatever. Enjoy!

• simple-dispenser.pdf
• simple-dispenser.io - Bricklink Studio file

LEGO coin sorters and LEGO automata are also fun little builds. Looking forward to sharing those eventually. In the meantime, there are plenty of tutorials and cool videos around. Happy hacking!