Robotics Project Two: Vending Machine

The Mechanism of our Vending Machine

First you the user has to step up to the machine and in front of the machine. This will activate the Ultrasound sensor and start up the conveyor belt.

After the machine senses you it will wait for you to insert a blue HK20 dollar bill into the machine. But sadly EV3 does not let you select specific colours and the blue on the HK20 bill was not one of them. So instead if you use a blue lego piece or a solid blue anything it should trigger the light sensor and move on to the next step.

Light sensor


After if a valid note is scanned it will allow you to push any touch sensor three times. This means you can have three different choices for your 20 dollar bill and means you can choose what ever combination of the three options that you want (a, a, c, or b, c, b, or even, a, b, c).

ButtonsAfter you have chosen your three selections those will than be carried over to our motors that will dispense our choices.



  • The Circular motion from the motor is converted in to linear motion which is used by the axle

Final Product




One of the flaws inside of this machine is that the conveyor belt is slightly obstructed and because of this the conveyor belt will periodically fall off or stop working entirely. This can be fixed by moving the obstruction (the ultrasound sensor) up above or around this key component.

Another flaw of this machine is that it doesn’t have a sturdy frame that it can rely on for a strong support. This is a problem because say if the conveyor belt falls of it would cause a chain reaction and eventually destroy our whole machine. To do this you would need more beams and axles as this would stop the pieces from becoming loose and unreliable.

A final flaw is that the EV3 light sensor will not scan whatever colour you want it to scan. It will only scan for a list of 7 different colours which disables us from using a bill in our project. To make up for this we have used lego pieces and paper “notes” to activate the machine. This is out of our hands to fix but if it is ever resolved it will allow this project to show its true potential.


Leave a Reply

Your email address will not be published. Required fields are marked *