Process

How it works

I used 4 pairs of IR break beam sensors for four slots I laser cut. They will detect when the beam is broken and change the corresponding amount. When you insert a coin, the coin will slide on a slide made of mat board with holes I laser cut on it. Each hole is the same size as a coin. Under the hole, there is a pair of IR Break Beam sensor. When the coin falls, it will break the beam and the sensor will detect and update the amount of money. LCD will show the total amount of money.

The Build

Physical

I made the hole for insertion oblique because I want the slide inside to be oblique so that coins can easily fall into the holes that are aligned on the side of the slide.

I also made a second floor to with long holes so that it can hold my breadboard and enable the wires to go through. 

Circuit

The Story Behind

After I had the idea of making a smart piggy bank, I thought the inner system of a vending machine should be a good reference. However, the way vending machine recognizes coins is way too complicated and requires delicate accuracy. A more straight forward way might be having different slots on the outside, but the problem is the count would be incorrect if the coin is thrown into the wrong slot. So, there you go, I hided slots inside and made an oblique slide so that it solves that issue and looks smarter!