How do they recognize the money you insert?
Coin-operated vending machines work by detecting inserted coins through physical and electronic mechanisms. When a coin is inserted into the vendor’s slot, it travels down a specially angled chute. It is angled to generate a set amount of momentum for the travelling coin.
The currency then passes through an electromagnetic field generated by an electromagnet that surrounds the chute, generating an electronic signature according to its chemical composition. If this signature doesn’t match one of the vendor’s computer’s known set of signatures (the different coin values) the coin is not logged by the system, but rejected.
If coins pass both checks, they are logged and accepted by the vending machine and function accordingly; if either check fails, however, the coin is rejected and sent down a second chute for collection.