無線電門戶警報器

步驟1：製作

它是什麼？

當有人打開門或門一直開著時，會發出無線警報來警告您。

How to make it

• You will need two micro:bits with different code on each. One micro:bit acts as a radio transmitter and the other as a radio receiver.
• Attach the transmitter micro:bit and battery pack to the corner of a door frame and attach a magnet close to it on the corner of a door.
• Place the receiver micro:bit anywhere nearby.
• If the alarm doesn’t work as you expected, you may need to change the magnetic force strength number in the transmitter code. Pressing button A shows the current magnetic force reading. Use this to decide on the threshold number, taking readings with the door open and closed.

運作方式

• The transmitter program uses the micro:bit’s compass (magnetometer) input sensor and a loop to measure the strength of the magnetic field every two seconds.
• It uses selection so when the magnetic field strength falls below a certain level (the threshold), it sends a radio signal ‘open’. If the magnetism reading goes above the threshold, it sends the signal ‘closed'.
• When the receiver micro:bit receives the signal ‘open’, a cross appears on its LED display and an audible alarm sounds. When it receives the signal ‘closed’, a tick appears on its LED display and no sound plays.

你需要的東西

• two micro:bits and at least one battery pack
• 一塊磁鐵
• some adhesive putty to fix a magnet to a door and a micro:bit to a door frame
• if you have a V1 micro:bit and want to hear an audible alarm, optional headphones, buzzer or speaker and crocodile clip leads to attach them

步驟2：編碼

傳感器/發送器:

1from microbit import *
2import radio
3radio.config(group=17)
4radio.on()
5
6while True:
7    if button_a.was_pressed():
8        display.scroll(compass.get_field_strength())
9    if compass.get_field_strength() < 100000:
10        display.show(Image.DIAMOND_SMALL)
11        radio.send('open')
12    else:
13        display.clear()
14        radio.send('closed')
15    sleep(2000)
16

警報/接收器：

1from microbit import *
2import music
3import radio
4radio.config(group=17)
5radio.on()
6
7while True:
8    message = radio.receive()
9    if message:
10        if message == 'open':
11            display.show(Image.NO)
12            music.play(["C4:4"])
13        if message == 'closed':
14            display.show(Image.YES)
15

步驟3：進階

• 使用多個micro:bit透過發送不同的radio訊息來追踪不同門的狀態，例如 “後門打開”。
• 使用variable來測量門打開的時間－可以幫助您節省加熱能嗎？