Module Project

Mini Coin Operated Snack Machine

Description

It dispenses snacks(sweets), using a gravity feed magazine, whenever a coin is inserted. After inserting a $1 coin, the user can select between two options through the push buttons. Servos are used to dispense the snack and return the coin.

Fabrication techniques

Technique Makes
Laser Cutting Casing and Dividers
3D Printing Dispensing Mechanism
CAD Design Hardware design and patterns for engraving
Processing System Arduino Uno or compatable CPU
Input Devices Push Buttons, PIR Sensor
Output Devices Servos, LEDs
Power Single 5V DC plug

Bill of Materials

No. Quantity Description Cost (each)
1. 1 Arduino Uno or compatable CPU $6.50
2. 3 Mini Servo $2.45
3. 3 2-Pin Mini Pushbuttons $0.06
4. 5 LEDs, white x2, yellow x3 -
5. 1 PIR Sensor $1.50
6. 1 A2 3.5 mm Ply Wood -
7. 1 A3 3 mm Clear Acrylic -

Computer Aided Design (CAD)


I started of by creating the base followed by the other sides of the housing, i also created slots for the shelfs and partitions.


After creating an offset plane and sketch,i projected(Create > Project/Include ) the outline and slots from the left and right profile to create the divider.Then i created the back panel.


Next, i designed the front panel which consist of 2 pieces, the first piece is made of wood while the second piece is made of acrylic. I designed openings for the buttons, window, coins and push door.


I made a hole which acts as a hinge for the push door, after that, i designed the push door for the 2 compartments.


I then design the shelfs for the vending machine, i included openings and holes to mount the servo that is used for dispensing.


After that i created more dividers, to seperate compartments and also to hold the snacks.


I made a slope which sorts out $1 from the rest of the coins. The hole i made is slightly smaller than a new $1 coin.


Next i designed a mechanism to return and deposit the coin, i also designed a slot to mount the servo.


I designed a linkage to link the servo to that mechanism and also a housing to house the push buttons and LEDs.


Lastly, i designed an attachment for the servo to push and dispense the snacks. I also designed a movable partition so that i am able to fit snacks of different length.

3D Printing


Go to Tools > Make > 3D Print and select the parts to be printed. Save it as Stl.


Open the stl file in Cura, change the settings and slice it.

Slicing Parameters

3D Printed parts



Laser Cutting


After finishing the design, i created a new sketch on each profile and save it as DXF.


Open inkscape and go to File > Import to insert the DXF file. The canvas size can be changed at File > Document Properties.


Parts

Programming

Testing of dispensing mechanism and program.

Assembly


Firstly, assembled the front, base and divider, the pieces are a bit loose, therefore i added glue.


I assembled the coin return mechanism and realised that the slope angle is not enough for the coin to slide.


To solve that issue, i changed the position of the linkage, it have lesser mechanical advantage, but the servo to strong enough.


I glued the rest of the parts and used rubber bands to hold it tight.


Next, I assembled the dispensing mechanism and partitions.


At first i wanted to use an arduino nano board, but i realised that there is enough space to fit the bigger uno board.


I replaced the screws with a longer one and mounted it onto the divider together with the breadboard.


After that, i connected the wiring the same way and also organised the wires with cable ties.


Lastly, using a pen knife, i cut a hole on the back plate for the USB cable and 5V power supply. I also 3D printed a part to cover the edges to make it look nicer.

Finished Product

All Files

Click here to download files.