What students build
- A button input
- A buzzer or simulated sound
- Visible status output
- Armed and disarmed states
- Acknowledgement or reset
- Test cases
Guided Project
Guided ProjectButton and Buzzer Alarm
Protect a small imaginary vault with an alarm useful enough to detect a press and polite enough to stop.
Project brief
What students learn
- Input-process-output
- Digital signals
- Conditions
- State
- Feedback
- Circuit or simulation debugging
What students need
- Browser circuit simulator
- Optional button, buzzer, microcontroller, and suitable supervised components
The circuit can be built in a browser simulator. A physical version uses teacher-arranged components and a safe buzzer volume.
Suggested build order
- 01
Read the button
Task: Display or log pressed and not-pressed states.
- Checkpoint
- Input changes are visible.
- Likely mistake
- Code listens to the wrong input.
- 02
Control one output
Task: Connect the input condition to sound or a simulated buzzer.
- Checkpoint
- The output responds for a clear reason.
- Likely mistake
- The buzzer never turns off.
- 03
Add visible feedback
Task: Show ARMED, TRIGGERED, or DISARMED.
- Checkpoint
- The current state is always understandable.
- Likely mistake
- Display and output disagree.
- 04
Create reset behaviour
Task: Choose how the alarm stops and returns to armed.
- Checkpoint
- Reset does not immediately retrigger.
- Likely mistake
- The pressed button remains true during reset.
- 05
Test sequences
Task: Try press, hold, release, reset, and repeated press.
- Checkpoint
- Every sequence has a defined result.
- Likely mistake
- Only a quick tap is tested.
Test questions
- What happens while the button is held?
- Can the alarm be disarmed?
- Does reset retrigger immediately?
- Does visual state match sound?
- Can repeated presses break state?
Common mistakes
- The output has no off path.
- State display is decorative rather than connected.
- Reset ignores the current input.
- Sound volume or duration is not considered.
Extension ideas
- Add a delay before arming.
- Require an acknowledgement input.
- Count trigger events.
- Create a silent visual alarm mode.
Challenge levels
Builder
Make press and release behaviour reliable.
Inventor
Add armed, triggered, and reset states.
Boss Level
Design two inputs and a clear alarm priority rule.
What to demonstrate
- Readable input
- Controlled output
- Visible state
- Reliable reset
- Held-button test
- One state bug explained