Lesson 5 Pupil Notes
Title
Distance Sensing With HC-SR04
Big Question
How can the board measure distance using sound instead of touch?
What This Lesson Is About
The HC-SR04 sensor sends out an ultrasonic pulse and waits for the echo. The board measures the return time and uses that timing to work out distance.
Key Words
- distance
- ultrasonic
- echo
- sensor
- centimetres
- timing
Before You Start
- Open the sonar panel.
- Keep the space in front of the sensor clear.
- Be ready to move an object slowly closer and farther away.
What To Remember
- the HC-SR04 sends out a sound pulse
- the sound bounces back from an object
- the board measures the return time
- time can be turned into distance
- live sensor values can drive display behaviour
What We Did
- viewed live distance readings
- moved objects closer and farther away
- watched the value change in real time
- linked distance values to display behaviour
What To Look For
- how stable is the reading?
- what happens when an object moves quickly?
- what kinds of surfaces might give stronger or weaker echoes?
Try This
- Hold an object still and note the reading.
- Move it closer and watch the value change.
- Move it away and compare the response.
- Use the value in a rule or behaviour if available.
Why It Matters
This is a strong example of a real-world event becoming a number the system can reason about.
Check Yourself
- What does the sensor send out?
- What is an echo in this lesson?
- Why does timing help measure distance?
- Why might readings change when the object moves?
Reflection
- A distance reading I saw:
- What changed the reading:
- One situation where this sensor would be useful: