Model 4: Distance measurer

Measuring and surveying

Grade

5-7

Time required

2-4 double hours

Difficulty level

Modell: medium, Programmierung: medium to hard

Model type

mobile device for distance measurement for near and distant targets

Download didactic material

MODEL DESCRIPTION / TASK

The pupils (SuS) plan and realize a portable rangefinder. The device should be usable for small and medium distances. Three colored LEDs display the distance measured by the device in the form of colored pulses (units, tens and hundreds). The data can be displayed again after the counting process using another button. The displayed values are added together by the user to form a total distance. The device resets itself when a new measurement is taken. Shorter or longer distances can also be measured by simply redesigning or reprogramming the device. As a challenging differentiation task, the pupils can work on reading in, temporarily storing and redisplaying the measurement results by pressing a button.

EVERYDAY RELEVANCE

Recording and outputting distances is not an unfamiliar topic for pupils, as is counting using a pulse generator (this is usually familiar from the bicycle speedometer). The effect of the pulse generator can even be observed in small children's toys (e.g. a wobbling duck).

The topic provides a good basis for pre-professional orientation in the field of coding. This is becoming increasingly important in many modern (technical) professions.

Key questions

Where are distance meters used in everyday life? (Communication)
How or with which simple technical means can a distance be measured? (Communication)
What problems can occur during use? (critical thinking)
How must the distance meter be constructed in relation to the housing and the associated programming (distance to the measuring device) in order to record exact measuring points? (creativity and collaboration)

Subject reference

Computer sience

Basics of programming, time loops

Mathematics

Conversion factors, conversion of number from different systems

Technology

Construction technology, gear theory

Physics

Route, distances

Lesson progression

Lesson discussion (without app)

Query scenarios in which distance measurement is required.
Work out the precision of distance measurements (1 m, 10 m, 100 m)
Work out various possible sensors that can be used to measure distances (e.g. in everyday devices).
Presentation of the task.
Work out the transmission ratio required for the supplied impeller. For this purpose, the rolling circumference of the wheel is recorded and the pulse frequency of the clock generator is explained.

Assistance if necessary

Show sensors, actuators and components (impeller for measuring circumference) from the kit, use presentation media if necessary

Lesson discussion

The teacher specifies the procedure using the work steps in the app.

Partner or individual work (with app)

Pupils familiarize themselves with the app and download the corresponding task.
Pupils work on a task to set up the system and calculate the distance counter.

Optional partner or group work (without app)

Pupils sketch a possible system
Pupils discuss the results and agree on a design.

Partner or individual work

Pupils use the app to build the rangefinder. The app guides them through the program in small steps.

Partner or group work

Pupils write the program for the range finder. The app guides them through the program in small steps
Help is offered in the app
The program is transferred to the RX controller

Partner or group work

The rangefinder is put into operation
Possible malfunctions in the function sequence must be found and rectified. Help is offered in the app.
Possible optimizations can be made to the hardware (e.g. mounting the wheels, rotating rollers) and the programming

Optional: Presentation of an allocation of the differentiations

The possibility of differentiation for fast pupils is offered in the app:

Differentiation 1: The counting wheel can be marked so that the starting position can be recognized. The LEDs can also be labeled (on adhesive labels). This makes it easier to read the units. Material for this must be provided.
Differentiation 2: The system can be programmed so that the shortest distance is reduced (halved) to 2 cm by tapping the edge change from positive to negative edge.
Differentiation 3: The system can be designed with a gearbox extension so that greater distances (e.g. 2.1 km) can also be determined.
Differentiation 4: The system can use an additional button to display the previously saved measurement results at the touch of a button via the three LEDs.

The further procedure is implemented using the app.

Discussion in plenary

Debriefing of the project in class.
Strengths and weaknesses of the individual group solutions or of distance meters for short or long distances are identified and discussed.

Information and notes

Methodical and didactic tips

Didactic note

Due to the complexity of the model, it is recommended that the way meter is only worked on at the end of the respective learning unit. The programming skills required are quite complex, and the knowledge on which the programming is based (see Programming skills) should already have been learned and applied in other models. For this reason, there are no step-by-step programming instructions in the part for pupils; the primary calculation of the measurement factors and the subsequent conversion of numbers from different number systems are relatively demanding for pupils. For this reason, the Ss section focuses on the necessary conversions and pulse/edge control.

Differentiation options

The LEDs can be provided with markings on labels to make it easier to read the units. The starting position on the wheel can also be marked with a colored marker.
If required, smaller distances or longer distances can be measured by changing the programming or hardware.
The measurement results can be temporarily stored in a variable. Using a conversion algorithm, the measured values can then be recoded into multiples of 2, 10 and 100 by querying the measured value and displayed by means of an LED after pressing the second button. This program is very complex due to the recoding, divisions with remainder, use of counting variables and the necessary call of a subroutine and should only be given to advanced pupils as a differentiation task.

Competition

The distance meters with the greatest measuring accuracy should be determined in a practical application under competitive conditions.
Various measurements of known and standardized distances, e.g. 400 m race track on the sports field, can be carried out.

Motivational Aspects

Recording analog data, converting it into digital data and outputting the results is highly motivating for pupils. Converting one quantity into another presents a certain challenge. The topic provides a good basis for coding, which is becoming increasingly important in many professions.

Additional materials

If necessary, use a real object to introduce the topic:

Visual aids in the form of simple rollers or wheels to show the distance covered in one revolution.
If necessary, various commercially available distance meters that can be triggered manually, e.g. bicycle speedometer with Hall sensor.
Optional: Drawing media (paper, whiteboard or projection surface)

Building instructions

Circuit diagram

Funktions of the model and their technical solutions

Function of the distance meter

Technical solution

Start of the measurement process

Travelling the distance to be measured

Recording a distance/path

Pulse generator on the counter wheel outputs data

Output of the measured distance "4 cm"

Color output of the green LED

Output of the measured distance "16 cm"

Color output of the yellow LED

Output of the measured distance "64 cm"

Color output of the red LED

Output result

Output of the LED by pressing the button

New measurement

Restart the system

Material list

Sensors

Function

1 impeller on a shaft

Detection of the disctance 1

1 button

Pulse counter

Differentiation 4: 1 push-button

Intermediate storage and later retrieval of measurement results via 2nd button

Actuators

Function

1 LED, green

Output for 2² units, e.g. 4 cm or multiples thereof

Differentiation 2:

Units of 2, e.g. 2 cm or multiples thereof

Differentiation 3:

Display of the measurement results for multiples of 2 cm

1 LED, yellow

Output for units of 2⁴, e.g. 16 cm or multiples thereof

Differentiation 2:
Units of 10, e.g. 100 cm or multiples thereof

Differentiation 3:
Display of the measurement result for multiples of 10 cm

1 LED, red

Output of units of 2⁶, e.g. 64 cm or multiples thereof

Differentiation 2:

Units of 100, e.g. 100 cm or multiples thereof

Differentiation 3:
Display of the measurement result for multiples of 100 cm

Differentiation 3:
Gearbox on the shaft

Enlargement of the possible measurement paths / measurement results