Arduino Uno R3

Detect a knock with the piezo

Use the kit piezo as a vibration sensor, observe its brief analog signal, and calibrate a knock threshold from evidence.

CSTA 2026 mapping candidatesNot reviewed by CSTA

MS-DAT-DI-27Data & Analysis

Students will

Explain how the piezo can act as either an input or output
Capture and compare brief analog peaks
Calibrate and test a knock event without assuming a universal threshold

Evidence of success

A table of baseline and tap readings
A threshold justified from observed peaks
Ten trials that distinguish intentional knocks from ordinary vibration

Hardware

Arduino Uno R3
Starter Kit piezo capsule
1 MΩ resistor
Breadboard and jumper wires
Stable mounting surface

Prerequisites

Read an analog value
Open Serial Monitor
Choose a threshold from repeated measurements

Before class

Verify the actual piezo part and reviewed polarity guidance
Prepare the 1 MΩ resistor used across the sensor in the reviewed input circuit
Provide a repeatable mounting and tapping method

Reviewed connection map

Piezo vibration input

PiezoMechanical vibration creates a brief voltage

A0Analog peak measurement

Reviewed resistorPlaced across the piezo in the Starter Kit circuit

GNDSignal return

Build the reviewed Starter Kit knock-sensor circuit with power disconnected.
Connect the signal to A0 and secure the piezo before calibrating the threshold.

Build and test

01With power disconnected, connect the piezo to A0 and GND with the 1 MΩ resistor across the sensor
02Print the raw A0 reading and observe the resting baseline
03Apply ten gentle taps, recording peak values and missed or false events
04Choose a threshold above the resting noise and below most intentional taps
05Test the threshold with normal table movement and revise it for the installation

Read before uploading

Annotated Arduino sketch

const int PIEZO_PIN = A0;
const int LED_PIN = LED_BUILTIN;
int threshold = 100;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int reading = analogRead(PIEZO_PIN);
  bool knock = reading >= threshold;
  digitalWrite(LED_PIN, knock ? HIGH : LOW);
  if (knock) Serial.println(reading);
  delay(10);
}

Optional engineering record

Record evidence from this lesson

Choose the prompts that help students explain predictions, evidence, debugging, and transfer. Saving creates a new entry in this browser’s Rudi notebook.

Record your thinking — optional4 prompts

Use these prompts if they help students capture evidence, decisions, or questions. You do not need to complete every prompt or create an entry at every step.

Predict: Before you begin, what do you expect to observe when you explain how the piezo can act as either an input or output?Evidence: What evidence best demonstrates this result: A table of baseline and tap readings?Debug: If you encounter “Every small movement triggers an event,” what will you check first, and why?Transfer: Where could you reuse the skill from “Detect a knock with the piezo” in another classroom project?

Nothing is saved until you choose this button.

Troubleshooting

Every small movement triggers an event

Secure the piezo, raise the threshold from recorded evidence, and separate taps with a short quiet interval.

Strong taps produce no reading

Verify A0, GND, the resistor placement across the piezo, part condition, and Serial Monitor timing.

2026 middle school standards

Potential CSTA connections

Not reviewed by CSTA

These are evidence-based crosswalk candidates for curriculum review—not a claim of official alignment.

MS-DAT-DI-27

Summarize a data investigation process, including potential biases, limitations, and supporting evidence.

Students collect repeated sensor readings, identify limitations, and support a threshold or response with evidence.

Lesson evidence: Knock and background reading table

View the official 2026 CSTA standardsStandard text: Computer Science Teachers Association (2026), CC BY-NC-SA 4.0.

Supporting concepts

ohms-law · power-and-signals · sketch-foundations

Sources and review

Arduino Uno R3 documentation Arduino Projects Book · CC BY-NC-SA 3.0 Arduino Knock example

Starting point, not verified curriculum. Review the actual hardware, circuit, code, power requirements, and classroom conditions.

After teaching this lesson