Breakfast cereal is controversial. Milk or cereal first? Best cereal to milk ratio? Favorite cereal? Most attractive mascot? The opportunities for debate never end. But we can all agree that consistency is key when it comes to the milk:cereal ratio — nobody changes that up from day to day. To ensure that every pour is perfect, Engineering Dads built this cereal and milk dispensing machine.

This machine pours dry breakfast cereal from a hopper and pumps milk from a jug, so the hungry user only needs to place the bowl and lift the hopper door. That is nice and automatic, but the more important feature is the ratio adjustment. The user can turn a dial to tweak the amount of milk dispensed with each serving, while controlling the cereal quantity by lifting the hopper chute door to a specific height. A movable sensor detects that door and triggers the milk pump when the door reaches that desired height. 

Engineering Dads designed an Arduino UNO Rev3-based circuit to control that functionality. It reads the voltage from the potentiometer to determine the amount of time to power the milk-dispensing pump and it starts that process when it detects a change from the photoresistor. The hopper door moves in front of the photoresistor, blocking the light to kick everything off.

The hopper and electronics enclosure were 3D-printed, which brings up an important point about food safety. 3D-printed parts are generally not food-safe (even if the filament material is), because bacteria can collect in the layer lines and sanitization isn’t easy. But Engineering Dads coated the prints in a layer of epoxy to create a smoother surface and that may help — though they’re not making any guarantees.