# 3.3 PIR Motion Sensor

## 3.3.1 Overview

The PIR motion sensor adopts RE200B-P element. 

Based on pyroelectric effect, the sensor is able to detect the infrared ray emitted by human body or animal. With Fresnel lens, it can even detect farther and wider. When a nearby human or animal motion is detected, the sensor outputs a high level.

##  3.3.2 Schematic Diagram

![6-3](./media/6-3-2.png)

**Working principle:** The human body maintains at 37 degrees, so it will emit a specific wavelength of about 10μm infrared. The sensor captures 10μM infrared to determine whether there is a motion.

## 3.3.3 Code Blocks

1. ![j15](./media/j15.png) 

   This block reads PIR motion sensor value. If there is a human motion, it outputs 1; otherwise, it outputs 0. 

2. ![j16](./media/j16.png) 

   This block determines whether a condition is satisfied. If yes, code in “if” will be executed. Or else, code in “else” will be executed.

## 3.3.4 Test Code

## 3.3.4.1 Build Code

There are two ways to upload the code: directly open the code file we provide; or manually build blocks.

**Directly open the code file we provide:**

1. Click ![](./media/j68.png) and choose `Load from your computer`

![](./media/j67.png)

2. We have already downloaded the codes on computer desktop, so open the file and choose `3-3-pir.sb3`

**Manually build blocks:**

1. In ![events](./media/events.png), find ![j1](./media/j1.png) block.

2. In ![serial](./media/serial.png), find ![j12](./media/j12.png) block and set baud rate to 9600, and put it under ![j1](./media/j1.png).

3. In ![control](./media/control.png), drag ![j2](./media/j2.png).

   ![6-4-4-1-1](./media/6-3-4-1-1.png)

![6-4-4-1-2](./media/6-3-4-1-2.png)

4. In ![control](./media/control.png), drag ![j16](./media/j16.png) into ![j2](./media/j2.png).

![6-3](./media/6-3-4-1-1.png)

5. In ![pir](./media/pir.png), find and put ![j15](./media/j15.png) into the condition box of ![j16](./media/j16.png). 

   Add the following block under "if": ![6-3](./media/6-3-4-1-2.png) prints “Someone!”; Add the following block under "else": ![6-3](./media/6-3-4-1-3.png) prints “No one!”

**Complete Test Code**

![6-3](./media/6-3-4-1-4.png)

## 3.3.4.2 Test Result

After uploading code, when human motion is detected, the monitor prints “Someone!”; If not, it shows “No one!” (Note that click ![6-2](./media/6-2-4-1-4.png) to set the baud rate before uploading code to avoid garbled words.)

![6-3](./media/6-3-4-2.png)