Model 8: Candy machine

Give me candy!

Grade

6-8

Time required

2 Double lessons

Difficulty level

Modell: medium, Programming: hard

Model type

Vending machine: a stationary device, individually fillable for dispensing various small items (candies, pills, dietary supplements)

Download didactic material

MODEL DESCRIPTION / TASK

Students plan and implement a vending machine for storing and dispensing small items, such as candies. The selection of the desired product on a motorized turntable is done using a button. The product is visible but not yet accessible. Only through an access system using a magnetic switch (Reed contact) can the product be retrieved. This opens a motorized access security mechanism.

To expand the system, an alert lamp (LED) can be integrated to indicate when the product can be safely retrieved. Before closing the security mechanism, this lamp blinks as a warning.

EVERYDAY RELEVANCE

The automatic operation of a machine and the dispensing of an (edible) item have a strong motivational effect on students. Many comparable solutions are known from everyday life (gum vending machine, beverage dispenser, bumper cars, etc.). However, the incentive to manipulate a professional system to one's advantage is also recognized. This leads to considerations on designing their own solution to be transparent yet also as tamper-proof as possible.

Key questions

What functions need to be fulfilled for the encoded triggering of an operation? (Communication and collaboration)
How can the goods contained in the machine be selected by the user? (Communication and collaboration)
How can the goods in the machine be protected from access or how can access be granted? (Creativity and critical thinking)
What aspects of the design need to be considered to protect the machine from manipulation and ensure robustness? (Creativity and critical thinking)

Fächerbezug

Informatics

Basics of programming, switches, sensors, time loops

Mathematics

Angle of a circle

Economics

Sales strategies

Physics

Capturing physical quantities (rotational angle, end stop)

Lesson progression

Information and notes

Methodical and didactic tips

Differentiation options

The system can be supplemented with a green LED and programmed to provide visual clearance (green LED) when the product can be removed. A blinking function can also be programmed to indicate the closing of the access lock.

Motivationale Aspekte

Sweets themselves have a certain effect on students. However, the automated dispensing of tangible items (as opposed to just information) also holds an allure. The associated topic of manipulating information (in this case, input information) is familiar to students and relevant in many other aspects of life. Both factors contribute to fostering intrinsic motivation.

Additional material

Optional: Drawing media (paper, whiteboard, or projection surface)

Building instructions

Circuit diagram

Functions of the model and their technical solutions

Functions of the Actuators/Sensors	Technical solutions
Detecting a signal for the rotation of the goods warehouse	Analyzing the input button signal
Rotation of the goods storage	Control of the motor of the rotating carousel
Stopping position of the merchandise storage	Evaluating the cam-operated signal from the position switch
Verification of the legitimacy of the dispensing	Triggering the reed contact
Opening the access protection	Controlling the barrier motor using a time loop
Waiting time of the motor control for the product retrieval	Time loop
Closing of the access guard	Actuation of the barrier's motor via a time loop
Turning off the motor of the access barrier	Evaluating the signal from the limit switch
Differentiation 1: Visual indication that goods can be removed	Green LED blinking
Differentiation 2: Optical indication that access protection is about to close	Green LED blinking

Material list

Material list basic circuit vendor machine

Sensors	Functions
1 Push button	Signal for gearbox motor 1
1 Push button	Limit switch for gearbox motor 1
1 Push button	Limit switch for gearbox motor 2
1 Reedswitch	Signal for gearbox motor 1

Actuators	Functions
1 Gearbox motor 1	Rotation of the storage unit
1 Gearbox motor 2	Opening of the access guard

Material list Differentiationtask vendor machine

Actuators

Function

1 LED, green

Visual inspection lamp