How Does a Vending Machine Read Money?

Vending machines are ubiquitous in our society; people walk by them and use them every day. They are in offices, retail establishments, medical offices, public buildings, and sports facilities. People pull change and dollar bills out of the purses or wallets and pay to get food or drinks from an automatic vending machine. Did you ever stop to wonder how the machines knows what money you put in the slot? Did you ever wonder how the device knows whether you put in a one or a five-dollar bill?

For those of you who have contemplated the money-reading capabilities of vending equipment, the answers are really quite simple. Coins are read based on their obvious physical properties. Thickness, diameter, and ridges on the edge are the main characteristics read by a machines, but some advanced machines can also determine the chemical composition of a coin. For example, a quarter is 0.069 inches thick, 0.955 inches in diameter, and has 119 ridges around the edge. A nickel is 0.076 inches thick, 0.835 inches in diameter, and has a smooth edge, while a dime is 0.053 inches thick, 0.705 inches in diameter, and has 118 ridges along the edge. In an advanced machine, a coin passes through an electromagnetic field generated by an electromagnet; this creates an electronic signature based on its chemical composition. If this signature doesn’t match with a genuine coin’s signature, the coin is rejected by the device. Though it is quite simple to see how coins are read, paper money is a different matter.

Most people at some point in time wished that machines would read their one-dollar bill as a twenty, but unfortunately, this does not happen. Vending machines are smarter than they look and can tell what the denomination of the bill is without any issues (though we sometimes have difficulties getting a bill to go into the machine). Paper money printed in the United States contains many different security features designed to deter counterfeiters. There are also specific features which help with automated denomination recognition. One of the most common methods is through the use of a magnetic scan. Paper money is printed with magnetic ink which can be read by magnetic scanners. Another way that vending machines read paper money is with ultraviolet light. Vending equipment contains ultraviolet lights that scan inserted bills. These lights determine the value of the bill by reading the fluorescent response.

Some vending machines allow users to make purchases with credit cards and they read these cards like most other credit cards readers. They use a magnetic strip reader to measure and calculate the thousands of tiny magnets that comprise the strip on the back of the card. These tiny magnets, aligned in a specific way, convey information to the reader. When a credit card gets old, the integrity of the magnetic strip on the back of the card may have been compromised through damage or normal use; the magnetic strip reader can no longer read the information because the tiny magnets are no longer aligned correctly or some of them are missing.

Though it is human nature to seek ways to fool technology, vending machines, while not completely invulnerable to manipulation, are difficult to scam. Their technology is adept at reading all types of money and providing the correct amount of change. In a world filled with technological marvels, the good old vending machine still amazes with its simplicity and its near-perfection.