PJ008: Light Triggered Alarm Clock with Micro:bit

This project uses the Micro:bit's built-in light sensor to detect the environmental brightness, it sounds an alarm when the "day" gets bright enough from a dark starting, simulating a normal alarm clock, but without any tick-tock timing, programmed by MakeCode blocks. This project looks easy, but requires solid solution to achieve a reliable result, without non-stopping alarming, or unnecessary alarm when the "day" turning from bright to dark. Goals:

Consolidate knowledge: Input-process-output basic concept
Consolidate knowledge: Variable basic concept and if-else logic
Fun experience with Micro:bit built-in sensors and buzzer

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For your reference, here are some solution or creative result by our students, please mind that the demo there is not exactly in the required logic here.

23w16 Homework Show: Light Controller Alarm Clock

Effort Estimation

Prerequisite

Tools & Materials

Light Brightness Input from Microphone in Micro:bit

Task 1: Try A Simple Prototype

Task 2: Only Alarm for Dark->Bright Direction

Challenge Task 3: Add Calibration Mode to Set an Expected Brightness

Knowledge test, reflection and discussion

Referred/Used By

PJ008_light_triggered_alarm_basic_function.mp4

Demo of the basic function (Task 2)

PJ008_light_triggered_alarm_with_calibration_mode.mp4

Demo of the challenging task with calibration mode

PJ008_light_triggered_alarm_a_buggy_repeating_alarming.mp4

An example buggy result of repeating alarming

Effort Estimation

[ ] Simple: 30-60 minutes

[x] Moderate: 1-2 hours

[ ] Challenging: more than 2 hours

The estimation bases on average situation without unexpected troubleshooting, assuming that the student meets prerequisites. It only indicates rough time needed to complete this project, but not about technical difficulty, not covering discussion and sharing time. Here is a possible breakdown:

5 minutes: Understand requirement and solution, collect materials
10-15 minutes: Programming prototype, test and find out improvement points
20-30 minutes: Programming refinement, refactor and retest

Prerequisite

One should have prior knowledge

Tools & Materials

A laoptop or tablet with internet access
1x TM005: Micro:bit V2 board
MakeCode by Microsoft, the programming tool

Light Brightness Input from Microphone in Micro:bit

The light level is analog signal, and converted to a ranged integer result:

0 (darkness) ~ 255 (brightest)

Task 1: Try A Simple Prototype

Purpose: Get brightness input, use it to trigger an action when it reaches a specific level

Requirement:

Trigger alarm when the brightness reaches 128
The alarm should ring only 1 time, but not repeating/non-stop alarming

Test Cases:

Test with simulator in MakeCode and real target Micro:bit.

Test Case 1:
Slowly changing from dark to bright, somewhere in the middle point, the alarm rings, but only for once, should NOT repeat ringing.
Test Case 2:
Slowly changing from bright to dark, somewhere in the middle point, the alarm rings, but only for once, but repeating ringing.

Submit the Work:

Please submit your work to Google Classroom (here is a guide)

Examples & Tips:

Below are some examples by our students, not exactly working as expected, but for your reference, please fix any faults or bugs to make it working right

Task 2: Only Alarm for Dark->Bright Direction

Purpose: Use variable and if-else to reach an expected logic

Requirement:

Trigger alarm when the brightness reaches 128
The alarm should ring only 1 time, but not repeating/non-stop alarming
The alarm should only ring for dark->bright changing direction, but not the opposite way

Test Cases:

Test with simulator in MakeCode and real target Micro:bit.

Test Case 1:
Slowly changing from dark to bright, somewhere in the middle point, the alarm rings, but only for once, should NOT repeat ringing.
Test Case 2:
Slowly changing from bright to dark, the alarm should never ring.

Submit the Work:

Please submit your work to Google Classroom (here is a guide)

Tips:

Variable
If-else compound conditions, be careful with the logic in every detail!
Use "serial write" to add debugging logs

Why pause 1000ms? What if not pausing?

Test to see how reliable it is

When light level becomes from dark to light slowly, what happened when light level = 128?
What happens next?

Why setting last_light_level to "light level" on start?

Test to see how reliable it is

When light level becomes from dark to light slowly, what happened when light level = 128?
What happens next?

Challenge Task 3: Add Calibration Mode to Set an Expected Brightness

Purpose: Use variable and if-else to reach an expected logic

It's possible to calibrate an expected brightness level when starting up Micro:bit, please think about a solution and try out your ideas.

What we want in more details:

When Micro:bit starts up, give some hint to the user to give light input, i.e. entering a calibration mode
The user puts Micro:bit to an environment where the brightness level is as expected to be the alarming point
Micro:bit accepts the input light level, gives a hint to the user, now it's normal operation mode

Knowledge test, reflection and discussion

Purpose: Enhance basic knowledge understanding, reflect and summarize what we have learnt

Presentation & Demo

Share the work result with your classmates, friends or family

Tell what it is your product
Demonstrate how it works
Explain how it works

Review and discuss

Follow the tutor to take 5-10 minutes to review the questions and answers, correct some possible misunderstood issues or faults

Reflect for findings and questions!

Take 1-2 minutes to explore anything on the tools and the making flow, with curiosity, no matter how much prior knowledge you have, you should make

At least 1 interesting finding
At least 1 curious question

Flow Chart

Use your own way to visualize how the programming controlling logic is done, by a free style drawing, so that your friends can follow this flow-chart to reproduce the programming.

You might be interested to know what is "flow chart", click to learn more, but so far, it's not needed to be that serious, just draw something that can help you explain to your friends how the programming is made.

Referred/Used By

Used by LP2313: 10 Weeks Starting Package, 23w13
Used by LP2536.B: Practice Usage of Variables and if-else, 25w36