How Do Vending Machines Tell the Difference Between Fake Coins and Real Coins?

One of my life dreams as a child was to be able to fool a vending machine with quarter-like objects. I mean, how smart could a vending machine be, right? Wrong. More like how dumb a kid I was. Vending machines use light sensors to measure the size of a coin and electromagnets to detect the metal type to determine what kind of coin it is. If you’re not shaped like a quarter and built like a quarter, you ain’t a quarter in their book.


The whole system of what happens inside a vending machine is actually pretty interesting.


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True Story: 1st job at 16 was at the batting cages, with a small arcade. The old change machines from the late 80s/early 90s...this thing...

...the way it told the different between a $1 and a $5 was the picture of the picture of the president. I guess it has a rudimentary scanner or camera that can tell the difference. THere’s also something in there to tell if it’s a real bill or not? Not sure about the last one, BUT...counterfeiters would take real $1 bills and paste a xerox of Lincoln over Washington’s face to get $5 worth of quarters.

This happened at the batting cages. The very next day, Secret Service was there to collect the counterfeit money.