DFROBOT Motion Sensor Alarm User Guide

DFROBOT Motion Sensor Alarm

Specifications

• Hardware connections (Challenge 8-1): PIR sensor to pin P0, LED Strip to pin P1
• Variable types: Use numeric variables only in this lesson
• PIR behavior (for counting logic): PIR outputs HIGH for 2 to 3 seconds
• Mode options (Challenge 8-2): mode = 1 Disarmed, mode = 2 Home, mode = 3 Armed
• Expected mode actions: Home mode activates the camera view for 5 seconds when people pass by the door; Armed mode flashes warning lights (LED)

Quick Guide

1. Open the Coding page in Mind+ and connect hardware: PIR → P0, LED Strip → P1.
2. Challenge 8-1 (counting): Create a numeric variable named count, set it to 0, then add a block to change count by 1 when the PIR detects motion. Show the count on the screen.
3. Run the program; if the count jumps rapidly, add a wait 1 sec inside the loop to slow counting.
4. Set Button A to reset: when pressed, set count back to 0.
5. Challenge 8-2 (mode switching): Load program 8-2 and create a numeric variable named mode. Start with mode = 1.
6. In a forever loop, add conditional logic so each mode performs its action: mode=1 do nothing; mode=2 shows doorway monitoring; mode=3 flashes warning lights.
7. Use Button A and Button B to change mode (decrease/increase) during operation.

INTRODUCTION

Students will program with a PIR sensor to create a security alarm system that uses variables to store and modify data.

• can create variables and store numbers inside them.
• can adjust variable values to create a counting function.
• can use variables as mode switches to control program behavior.

Engage

5 min.
If someone walks by your door several times, could thesystemtell the difference between passing by and lingering?

Introduce the core idea: use variables to record doorway activity and switch security modes.

Background

5 min.

What is a variable?
A variable is like a named box that can store a number or text. In Mind+, we can create variables by clicking the Make a Numeric Variable button (only use the numeric variable in this lesson).

The set variable to 0 block assigns a new value to a variable.The change variable by 1 block increases the value in the variable by the amount you want.

Build and Connect

5 min.

No extra structures arerequired;students only needahousingblock to install hardware

After groups finish installation, prompt discussion:
Where should you place the PIR sensor to best detect doorway activity?
Prompt students to install the PIR sensor depending on the discussion.

Program

25 min.

Challenge 8-1: Entrance Monitoring System

1. Groups should opentheCodingpage in Mind+, connect theirhardware (PIR sensor topinP0,LED Strip to P1).
2. Guide them to create a variable called count and set it to0. Explain that this variable is for tracking each PIR detection.
3. Ask students to use a change variable by 1 block to count how many times the PIR detects motion. Challenge students to show the count on the screen so they can watch it climb in real time.
4. Ask students to run the program and let them observe. Guide themto addawait 1secblock inside the looptoslow

Extra Practice

5 min.
Ask students to improve the counter in Challenge

Make sure the count never goes below 1 or above 3.Ask students to combine the counter built in Challenge8-1withthe mode switch from Challenge 8-2, then add soundeffects.

NOTE: Two variables can work together—count tracks events, mode decides when to act.

Troubleshooting

• The count jumps rapidly instead of increasing once per pass: The PIR sensor outputs HIGH for 2 to 3 seconds, so the program can increment multiple times during that period. Add a wait 1 sec block inside the loop to slow counting.
• Mode values go out of the intended range: Ensure mode stays within valid bounds (the lesson practice suggests preventing mode from going below 1 or above 3).
• The system doesn’t appear to respond in a specific mode: Confirm your conditional checks match the lesson logic: mode = 1 (disarmed) → no action, mode = 2 (home) → doorway monitoring for 5 seconds, mode = 3 (armed) → LED warning/flash.