Coin Opreated Vending Machine Based on Microcontroller

average vending machines are commonplace at railway stations, airports, fast-food restaurants and even in companies. Press a switch and the machine delivers a cup of your favorite drink. This looks quite a simple operation but has a very complex logic behind it: It involves use of twelve precision timers and four counters apart from physical devices like display, solenoid and motor to deliver water and premixed tea/coffee/soup powder in exact quantity for better taste and in exact sequence. This has become possible because of the use of micro controllers, which allow compact size, higher reliability, lower cost and multiple functionalists. This tea/coffee/soup vending machine controller uses Free-scale latest AT89S52 micro controller chip. The controller is programmable and user friendly. You can set the quantity of the beverages through a button switch provided on the front panel of the controller as per your requirements. Thus, cups of any size can be filled at any time. But you can insert a 10RS. Coin in the system then is working. For human beings, recognizing if a coin is real is pretty easy. We can look at the coin, weigh it in our hand, feel the temperature, listen to it hit the floor, etc. If someone handed you a coin replica made of plastic, you would immediately know it is fake even if it looked authentic to your eyes. If someone handed you a blank steel slug, it would obviously be “not a coin” because it wouldn’t look like a coin at all. What we take for granted as humans is not so easy for a vending machine. A vending machine needs a relatively inexpensive way to detect if a coin is real.
Circuit Diagram:

Block Diagram:

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Be it schools, colleges or commercial establishments, vending machines, also known as automatic retailing, are everywhere. Most of the time,