Policeman | BOSON Inventor Series

0 333 Easy


In this workshop, students will construct a royal guard that starts patrolling when it detects someone approaching. They will learn basic knowledge of motion sensors and servos, wire up a circuit to facilitate the desired interaction, and finally, assemble a well-designed paper model to enhance its appearance and store all the hardware.

Student Age

Grade 1-3


45 min

Learning Objective

1. Get a brief understanding of the traditions of the royal guards

2. Learn the basics of motion sensor and servo technology.

3. Develop hands-on skills through practical application.

Project Goal

Using a motion sensor to detect human motion, the system controls the servo to swing left and right, imitating a patrolling stance when someone passes by.

Session Breakdown

Warm-Up | 5min | Exploring the Role of Royal Guards

Technical Analysis | 10min | The Basics of Motion Sensor and Servo

Hardware Connection | 10min | Connect the Circuit

Cubee Assembly | 15min | Assemble the Structure

Project Showcase | 5min | Test and Share the Project


During his trip to London, our buddy Mike noticed some cool folks with tall furry hats standing in front of the palace. Who are they? These guards aren't just protectors of the British royal family; they also play a significant role in ceremonies. Now, Mike's pondering: Could machines possibly lend a hand in security tasks?

Technical Analysis

Motion Sensor

All objects in the universe emit some level of infrared (IR) radiation, which is released as heat. This motion sensor is designed to detect changes in infrared radiation, thereby identifying the presence of a moving human or animal, and then outputting a digital signal. The motion sensor can detect moving objects within a 7m range with a 100° sensing angle.

Servo and Servo Controller Module

A servo is a rotary actuator used for precise control of angular position. The servo controller module is a servo driver that toggles between Swing and Turn modes, controlling the servo to make it swing back and forth or rotate to a set angle.

Swing: Swing between the preset angle and the initial angle.Turn: Rotate to a preset angle and stop.

Material Preparation

To realize the function, we will need the following modules and components.

Hardware Connection

Try to connect all the modules as the shown in the following connection diagram and see if it works out as what we’ve expected. Power the mainboard with either battery or USB cable. Don't forget to switch on the mainboard.

Test the frequency of the servo swing by gently rotating the blue knob on the servo control module.

Paper Module Assembly

Step 1: 

Place the electronic modules on the bottom board. Make sure the power plug of the mainboard is facing the gap.

Secure the servo in the groove with the blue piece of paper.

Step 2:

Thread the wire of the motion sensor through the wire hole and stick the sensor on the outside.

Assemble the bottom board with the hexagon cap. Check the direction of the cap to ensure a proper fit for the servo.

Step 3: 

Fold up the guard and secure the servo plate onto the circle at the bottom.

Step 4:

Place the guard on the servo. Connect the battery to the mainboard and don't forget to turn on the power switch.

Congratulations! You've successfully assembled your royal guard model. Now, it's time to witness its majestic patrol. Give it a go and see your creation come to life in the spirit of the royal guards. Unleash the royal magic you've crafted!

All Rights