Coin Based Cola & Soda Vending Machine

A demonstration vending machine for cola and soda. A coin authenticator verifies the coin, and motors in the fabricated frame dispense the selected can, showing how vending machines work.

The mild steel frame and fabrication forms the base that carries every other part, so it is designed first from the load and size of the machine. The Servo motor rotates to an exact angle, used for locks, arms and flaps. Motion is transmitted through shafts and linkages, cam and lever parts, which set the speed, torque and direction at the working end. The Microcontroller board processes sensor inputs and controls the outputs according to the program.

A microprocessor is only a CPU and needs external memory and I/O chips. A microcontroller has the CPU, RAM, ROM, timers and I/O on a single chip, which makes it cheaper and better for dedicated control tasks.

With a PWM signal at 50 Hz. A pulse of 1 ms gives about 0°, 1.5 ms gives 90° and 2 ms gives 180°. The internal feedback potentiometer holds the angle.

It is cheap, strong, easy to cut and weld and widely available. A frame of 25 mm square pipe is enough for most student models.

From the torque and bending moment it carries: d³ = 16 T ÷ (π × allowable shear stress) for pure torsion, with a factor of safety.

It converts rotary motion of the cam into reciprocating motion of the follower, with the displacement profile set by the cam shape.

Mild steel (MS) is used for the frame because it is strong, cheap, easy to cut and weld and available everywhere. Shafts are made of EN8 or bright mild steel for strength, and parts that do not carry load can be aluminium or acrylic to reduce weight.

A factor of safety of 2 to 3 is taken for static parts and 3 to 5 for parts under shock or fatigue loading. Allowable stress = yield strength ÷ factor of safety, and each part is checked against it.

The cost is the sum of raw material, bought-out parts, machining or fabrication and overheads. Our estimate for this model is about ₹9,000 to ₹13,200, depending on size, material and the workshop rates in your city.

Cutting and grinding of sections, arc or MIG welding of the frame, drilling for mounting holes, turning of the shafts and fitting of bearings and the drive, followed by assembly, alignment and painting.

Mainly open-loop: the controller runs the actuators for a set time or number of steps. Adding a sensor for feedback would make it closed-loop and more accurate.