Air quality testing

Why do I want to do this? Because I feel that the sky-high prices for air quality testing equipment on Taobao and Xianyu are too annoying. I clamped two pieces of acrylic together and closed the serial port. I asked for the price like crazy. It was really crazy. The bright red and green interface and the sparkling acrylic were so fun... It was really a huge profit, even higher than the various meters of ina226. Huge profits, because the difficulty is completely 0, and the various sensors are either serial ports or i2c, which is completely brainless. I have witnessed the craziness of water purifiers and air purifiers... I hope the bubble of air quality detectors will burst soon.

According to this tutorial, you can make a full-featured air quality detector with WIFI upload function, and various modules can be added or subtracted at will. By the way, let’s reveal the cost of air quality detectors.

The gas quality detector uses esp12-f as the main control. The peripherals that can be connected include:

• Climbing vine pm5003/7003 (measure pm1 pm2.5 pm10 particle count). ￥80
• Ccs811 (measures eCO2, TVOC, requires manual calibration, not recommended, very troublesome, the only advantage is that the bare chip is cheaper) ￥25
• Wz-sk (Measure formaldehyde)￥79
• Sht20 (temperature and humidity measurement)￥6
• IAQ core (measure eCO2, TVOC)￥65
• CM1106 or senseair s8 carbon dioxide sensor (or carbon dioxide sensor with the same package)￥150

The motherboard can be purchased for more than ten dollars. There is nothing you can do about the high price of the sensor. You can go shopping for some second-hand sensors. The carbon dioxide I bought was only 30 each, and the climbing vine was only 35.

Display Data:

• 0.96-inch OLED display (no casing, streaking, cost-effective, or use an electronic paper screen version of the casing)
• Electronic paper screen assembly (with designed casing).
• Connect to TLINK or onenet IoT platform to view data and curves through APP
• Connect to the AP launched by 8266 and open the web page to view the data
• The above methods can be freely combined and used at the same time

The power supply can be powered by USB or an external lithium battery (1.25mm 2pin interface). If a battery is not needed, there is no need to weld the components of the charge and discharge circuit.

• GPIO14     **** Carbon dioxide receiving
• GPIO12 PM2.5** Receive **
• GPIO13 ** CO2 Request **
• ** GPIO2     formaldehyde receiving **
• ** GPIO0     button **
• SDA oled ccs811 sht20 iaq core
• SCK oled ccs811 sht20 iaq core
• ** GPIO3 ** ( Rxd0 **** )
• GPIO1 ( Txd0 **** ) output electronic paper screen

PCB ** and BOM can be obtained from the link below. * GERBER *** file can be exported for proofing. For the purchase link, please refer to the file I uploaded.

https://lceda.cn/duck/kong-qi-zhi-liang-jian-ce

Welding precautions

1. If you do not need a charge and discharge circuit, you need to connect the two circular contacts on the upper left side of the circuit board.

2. Before soldering Sht20, find a piece of paper to cover the window. Do not use tape. Move quickly when soldering. Wait for a while after soldering a point. This component cannot be cleaned. Do not use flux that needs cleaning. Others The same as the sensor, it cannot be cleaned, washed with plate washing water, or smoked by rosin.

3. The circuit of Sht20 needs to be separated and connected with FPC cables, otherwise it will be affected by the heat of other components and the temperature and humidity will never be measured accurately (no matter which corner it is placed in or what slots are opened, it will not work. I have tried it).

Tutorial

1. Download the environment for compiling the program, plug in the USB cable, and upload the program (no need to manually enter download mode, no need to manually reset)

2. Connect to AP Air_sensors, open 192.168.4.1 to view data, set up WIFI connection, etc. The Air sensors connection point will always be open and can be connected at any time. When the mobile phone and device are connected to the same router, you can directly open http://air/ in the browser and view the data.

3. Connect to the onenet platform, register an account first, create a new device, and the protocol is HTTP. APP download https://open.iot.10086.cn/doc/art656.html#118

4. To transfer the configuration to the device, you need to transfer the city name (if there is an electronic paper screen), the device ID and key of the onenet platform, open the webpage to view the data and click Settings 

5. Send a message to the device. It will be received in 2 minutes at the latest and will jump to the display immediately. You can send monochrome pictures. Send text here duckweather.tk/client.php . The web page for sending pictures is under development.

6. Regarding the electronic paper screen components, you can check the BOM list by yourself https://lceda.cn/duck/kong-qi-zhi-liang-jian-ce-dian-zhi-ping-zu-jian . It is not difficult. Please pay attention. If you use flux, don't forget to wash it off, otherwise don't power on. Just upload the program after welding. It supports Weixue screen and Weifeng screen, and you can adjust it by yourself in the program. 

7. The screws that fix the shell and the circuit board are m1.6*8. The shell can be printed by the merchant according to the drawings. SLA photosensitive resin printing costs about 50 yuan.

Regarding accuracy: You don’t need to be so serious. After all, professional instruments cost tens of thousands of dollars. You get what you pay for, but it should be more accurate than the 19.9 and 29.9 on Taobao. Please check the sensor datasheet for details.

Please feel free to comment on whether it's possible, okay, okay, etc. It's just your personal needs.