Lesson 3 - Farm Panoramic Surveillance

joanne.zhao Jul 01.2026

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Lesson 3 - Farm Panoramic Surveillance: Sweeping Camera with a Servo

This lesson shows how a servo can turn the AI camera to remove the blind spot of a fixed camera. Students find the angle range in which face detection stays stable, watch the teacher build a sweeping scanner, then add their own intruder alert and simplify the program with a function.

I can explain why a fixed camera has a blind spot and how rotating it helps.

I can find the angle range in which the camera can stably recognize a face.

I can add a condition to detect an intruder and use a function to simplify my program.

1. Engage: Does a Fixed Camera Have a Blind Spot?

Open by describing the farm gate with a fixed camera: it only watches straight ahead, so someone can walk around the side without being seen.

2. Explore: How Wide Is the Camera’s View?

Set up the hardware connection (shown below):

Activity 1

Have students build and install the hardware following the Building Instruction.

Download the teacher-prepared program 3-1. Pressing A turns the servo 1° one way, and pressing B turns it 1° the other way.

Project Link

Have a student place the face card straight in front of the camera until the AI camera detects it.

Press A (or B) again and again, 1° at a time, until the face card is no longer recognized, then record the number of degrees. Repeat in the other direction and add the two numbers.

Have students complete the table, then discuss the results together:

Action	Expected result
Place the face card straight in front of the camera	Face recognized (✓)
Rotate left with A, 1° at a time, until recognition stops	About 5–10° (depends on distance and angle)
Rotate right with B, 1° at a time, until recognition stops	About the same as the other side
Stable range (left + right)	10-20°

Because the fixed camera only sees a narrow slice, it has to turn to scan—so we program the servo to sweep by itself.

3. Engineer: Make the Camera Sweep

Part 1 — Look at a Program with No Loop (sequence structure)

Show students the first program:

Key Question

What will this program do? Can it make the camera slowly turn left and right?

Teacher notes: It can make the camera sweep, but the program is long and not flexible.

Part 2 — Optimize with a Repeat Loop and a Variable (teacher demonstration)

Add extensions.

	Click Extensions
	Search “https://github.com/cdjq/pxt-expansion-board-for-microbit-k10”
	Add the extension
	Search “BOSON”
	Add the extension and go back to the coding page

Build the program.

Download the program and check the effect.

Run the program → the servo turns slowly from 0° to 180° and back.

Place a face card in front of the camera → it is detected as the camera sweeps past.

Teaching note: start with a small step (for example 1°) and a short pause (for example 100 ms); a smaller step and a longer pause make the sweep slower and smoother.

4. Experience & Challenge: Upgrade Your Surveillance

Experience: add an intruder alert

Activity 2

Ask students to add an if block inside the sweep: when a face is detected, trigger an alert.

Project Link

Students can choose their own alert—a buzzer, a sound, an icon, or a light.

Challenge: Simplify with a function

Have students run the program and look for blocks that repeat.

Key Question

Which parts of the program repeat, and how can we simplify them?

Activity 3

Challenge students to wrap the repeated blocks in a function and call it, so the program becomes shorter and easier to read.

5. See More: Cameras and Privacy

Key Question

Is it okay for a camera to watch everyone, all the time?

Explain that a sweeping camera is a kind of surveillance. It can keep the farm safe, but it also raises questions about privacy and who controls the data.

Think about it:

Step 1: Representation

The camera turns what it sees into data—pixels and features—that the AI reasons over. What the camera “sees” is only a representation of the real scene.