# 人體移動感應器(PIR)

人體移動感應器是很方便使用的電子模組元件，透過它可以偵測到附近是否有物體在移動，若有發現則觸發信號，電腦就可以利用這個觸發信號進行更進一步的活動，如閃燈、發出警告音等。

另外，日後的分享影音，將以gpiozero這個GPIO模組庫為主要對象，因為RPi GPIO是很底層的模組庫，要完成許多工作全部必須仰賴人工撰寫，因此在了解RPi GPIO的基本運作後，是時候離開它，並走向更方便的模組應用的時機了！

{% embed url="<https://youtu.be/mzRny98M4Qk>" %}

```python
from gpiozero import LED, MotionSensor
from signal import pause

led = LED(26)
ms = MotionSensor(17)

def some_one_here(pir):
    print('有人來了', pir.pin.number)
    led.blink(1, 0.5, 3)

ms.when_motion = some_one_here

pause()
```

如果是純使用RPi.GPIO，程式碼會變得較為煩人，但了解其底層的運作也不錯，程式碼如下，提供參考。

```python
import RPi.GPIO as gpio
from time import sleep

led = 26
pir = 17


def pir_checked(channel):
    print('some one here', channel)
    for i in range(3):
        gpio.output(led, gpio.HIGH)
        sleep(1)
        gpio.output(led, gpio.LOW)
        sleep(1)


gpio.setmode(gpio.BCM)

gpio.setup(led, gpio.OUT)
# 採用內建的下拉電阻
gpio.setup(pir, gpio.IN, gpio.PUD_DOWN)

try:
    # gpio.FALLING是指當電壓從高往下降時觸發事件
    # 這裡使用gpio.RISING是指當電壓從低往上升時觸發事件
    # 倒底要用哪個？會因為使用上拉或是下拉電阻的不同而不同。
    gpio.add_event_detect(pir, gpio.RISING, pir_checked, bouncetime=200)
    while True:
        sleep(1)
except KeyboardInterrupt:
    pass
gpio.cleanup()

```


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