自制甲醛测试仪

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因家里装修，自制了一个甲醛测试仪，在此记录下主要过程。

1.材料：

  • 1.树莓派Zero W
  • 2.ZE08-CH2O传感器（UART接口）
  • 3.ssd1306 128*64 I2C接口

其中，CH2O传感器是核心部件，主要用来采集甲醛含量。树莓派用来读取传感器上的数据，ssd1306用来显示数据。

最终效果如下图：

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2.接线方式

一、 树莓派Zero W引脚：

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二、 ZE08引脚

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ze08接树莓派：

ZE08 RpiGPIO
Pin4(5V) Pin2(5V)
Pin3(GND) Pin6(GND)
Pin6(UART-TxD) Pin10(UART-RxD)

三、 ssd1306 引脚

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ssd1306接树莓派（IIC协议）：

OLED RpiGPIO
VCC Pin1(3.3V)
SDA Pin3(SDA)
SCL Pin5(SCL)
GND Pin9(GND）

3.代码

代码

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import serial
import time
from time import sleep
import Adafruit_SSD1306
from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont
import subprocess


ser=serial.Serial("/dev/serial0",9600)



#init display
disp = Adafruit_SSD1306.SSD1306_128_64(rst=None)
disp.begin()
disp.clear()
disp.display()

width = disp.width
height = disp.height
image = Image.new('1', (width, height))
draw = ImageDraw.Draw(image)
draw.rectangle((0,0,width,height), outline=0, fill=0)

padding = 2
top = padding
bottom = height-padding
x = 0
font = ImageFont.load_default()
font = ImageFont.truetype("/usr/share/fonts/truetype/freefont/FreeSans.ttf",15)
cmd = "hostname -I | cut -d\' \' -f1"
IP = subprocess.check_output(cmd, shell = True )



def save(data):
    today = time.strftime("%Y-%m-%d", time.localtime())
    f = open(today,'a')
    f.write(data)
    f.write("\n")
    f.close()



while True :
    r_data = ser.read()
    sleep(0.3)
    data_left = ser.inWaiting()
    r_data += ser.read(data_left)
    if 9 != len(r_data):
        print 'error length: %d'%len(r_data)
        continue
    else:
        n=ord(r_data[4])*256+ord(r_data[5])
        ppm = str(n/1000.0)
        #print("CH2O:"+ppm) # ppm = n/1000.0
        save(ppm)
        draw.rectangle((0,0,width,height), outline=0, fill=0)
        draw.text((x, top),       "IP: " + str(IP),  font=font, fill=255)
        draw.text((x, top+15),     str(time.strftime("%Y%m%d %H:%M:%S", time.localtime())), font=font, fill=255)
        draw.text((x, top+35),    str("CH2O: "+ppm),  font=font, fill=255)
        disp.image(image)
        disp.display()

利用crontab实现监控

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#!/bin/sh
v_num=`ps -ef|grep "read.py"|grep -v grep |wc -l`
if [ $v_num -lt 1 ]
then
date
echo "read process die"
ps -ef|grep "read.py"|grep -v grep |awk '{ print $2 }'|xargs kill -9
cd /home/pi/m4bln
python read.py &
sleep 20
v_num=`ps -ef|grep "read.py"|grep -v grep |wc -l`
if [ $v_num -eq 1 ]
then
date
echo "reopen read process"
fi

else
date
echo "everything is OK :)"
fi

参考资料：

  1. 树莓派串口配置 https://www.abelectronics.co.uk/kb/article/1035/raspberry-pi-3--4-and-zero-w-serial-port-usage
  2. https://www.raspberrypi.org/documentation/configuration/uart.md
  3. ZE08-CH2O模组文档 http://style.winsensor.com/pro_pdf/ZE08-CH2O.pdf
  4. http://shumeipai.nxez.com/2017/09/13/raspberry-pi-network-configuration-before-boot.html 无屏幕和键盘配置树莓派WiFi和SSH