I’m working on a school project where I make a circuit board to emulate a snack machine and I’m wondering how to make a sensor that does this… but I don’t know how to tell a one from a five without using some kind of image scanner/filtering program and thats obviously not how it works since that sort of thing would be too expensive to add to a simple coke machine. Does anyone know how this sort of thing is done in the real-world industry?
You’d be surprised what goes into a "simple coke machine."
"Also known as bill validators or bill acceptors, paper currency detectors scan pliant currency using optical and magnetic sensors. Upon validation, the bill validator will inform the vending machine controller (VMC) or other host device of a credit via a parallel or serial interface. Various interfaces exist for the host device including a single-line pulse interface, a multi-line parallel interface, a multi-line binary interface, and serial interfaces such as ccTalk, SSP, MDB2PC and MDB2USB."
http://en.wikipedia.org/wiki/Bill_validator#Paper_currency_detectors
