🦅 ⏏️ 🐼 DIY electronic nose 👨🏿‍🤝‍👨🏾 🧑🏾‍🤝‍🧑🏾 🖖🏽

Working on previous projects with PM _2.5 particles[small, potentially inhalable particles, about 2.5 microns / approx. transl.] I noticed one inconvenience - I could not recognize the sources of pollution emitting small particles. Most of the data received on the earth and from satellites cannot tell you where the pollution comes from and how to get rid of it. I decided to upgrade the Honeywell particle sensor. He has his own fan, inlet and outlet openings, and I only had to think of a way to direct air flow from specific objects into it. And before that, of course, I already made a 3D model of the dog’s nose and printed it on a 3D printer. Therefore, I could only develop a case in the form of a pistol with a trigger, which would allow me to carefully examine the sources of particles that are killing for me.

Step 1: collecting materials

I used the Honeywell HPMA Particle Sensor because it is a reliable and inexpensive device. As in previous projects, I use the ESP32 microcontroller with integrated wireless communications.

1. Particle Sensor: HONEYWELL HPMA115S0-TIR PM2.5 Particle Sensor laser pm2.5 air quality detection sensor module Super dust sensor PMS5003 - $ 18

2. Wireless module: ESP32 MINI KIT Module WiFi + Bluetooth Internet Development Board D1 MINI Upgraded based ESP8266 Fully functional - $ 6 (AliExpress)

3. Power plate for the module: MH-ET LIVE Battery Shield for ESP32 MINI KIT D1 MINI single lithium battery charging & boost - $ 1 (AliExpress)

4. 18650 battery with wires - $ 4

5. Display: IZOKEE 0.96 '' I ²C IIC 12864 128X64 Pixel OLED $ 4

6. Power Button: Rugged Metal On / Off Switch with Green LED Ring - 16mm Green On / Off $ 5 (Adafruit)

7. 3D Printer (Ender 3)

8. Antrader KW4-3Z-3 Switch Micro Switch KW4 Limit $ 1.00

9. LED Ring Light: NeoPixel Ring - 12 x 5050 RGB LED with Integrated Drivers $ 7.50

Step 2: design and 3D printing

I specially designed the case so that the openings coincided with the fans built into the HoneyWell sensor, the nostril openings directly went to the sensor input, and the blown air exited through several openings in the fairing of the case (sorry that sounds like a patent application). The large handle allows you to place a fairly voluminous battery and the rest of the electronics. The charging port is flush with the bottom of the handle. The Neopixel ring should highlight the top of the case. The design is made so that the upper part of the case can be printed with transparent PLA, then switch to gray PLA for the handle, and again switch to transparent plastic at the bottom of the handle so that the indicator LEDs are visible during charging. The switching mechanism is equipped with a hinge and is printed together with the housing, but must move freely.

All files are made with the standard settings in the Cura program for the Ender 3 printer. No backups were needed.

content.instructables.com/ORIG/FYP/9343/K8CH414S/FYP9343K8CH414S.stl

content.instructables.com/ORIG/F93/2Q86/K8CH414T/F932Q86K8CH414T.stl

content.instructables.com/ORIG/FK2/96114/861UCH4K4KIUCH stl

content.instructables.com/ORIG/FT9/N577/K8CH414V/FT9N577K8CH414V.stl

content.instructables.com/ORIG/FUU/575L/K8CH414W/FUU575LK8CH414W.stl

content.instructables.com/ORIG/FSFS/BPDFUKW9B954KW9B9FK/KB854 .f3d

Step 3: connect

The connection diagram is practically the same as in my project of an analogue pollution meter for a bicycle [based, in turn, on the project of an amateur air pollution sensor ], except that there is no servo motor and the output is used for the data line of the Neopixel ring. In this case, the power button supplies battery power only to the power shield for the wireless module. The 5 V on the power plate is controlled by a limit switch in the handle, which works like a trigger. It supplies power from the shield to the sensor, to the ESP32, and to the Neopixel ring at the same time. Display I ²C gets 3V with ESP32. Most of the connection needs to be done before assembling the handle, passing the wires through the various holes. Be sure to pre-check the diagram on the prototyping board!

Step 4: Build

First, the Neopixel ring adheres to the nose body so that it does not warp or break its strong connection to the main body. Pass the three wires through the side hole of the main body and then into the handle. The Neopixel ring should look into the translucent part of the case. Then the air sensor is located in the case so that its inlet openings look towards the nostrils, and the fan blows back. Pull the wires from the back to the middle of the handle - there they will need to be soldered to the ESP32. Screen I ²C connects to the front, and its output wires pass through the slot into the handle and fit to the main board. The round visor then sticks over the screen. I use E6000 glue, but superglue will do. The nose with nostrils sticks to the front. The limit switch is connected to the wires and glued into place, like the main power button. The ESP board is inserted inside, after which the 18650 battery is installed. The power shield is glued to the bottom of the device so that the charging port is exactly opposite the hole. After checking the functionality, glue the bottom of the case to the case. The trigger is glued over the metal strip of the limit switch so that it is easily pushed to its lowest position. Caution - Do not glue the switch mechanism.

Step 5: program

The software uses a serial port to download information from the sensor. One of the problems with this sensor is that it does not use I ² C with libraries - that would be much easier. No servomotor is used as the output as the draft with a bicycle tow and SSD1306 bus I ² C. Ring Neopixel controlled via Adafruit Neopixel Library library, and produces one of the three colors, slowly changing brightness, and designating the level Card PM _2.5 in The nostrils. If the level is less than 25, it flashes blue, if from 25 to 80 - green, if above 80 - red. These levels are configured in the program code. You can also change the fonts and screen size. The sensor reads the information once per second.

content.instructables.com/ORIG/FG5/LCS8/K8CH74GE/FG5LCS8K8CH74GE.ino

Step 6: use

In the midst of quarantine with this device, you don’t particularly take a walk on the street, so I took a walk around the house and took video clips for YouTube to understand how bad things can be at home. So I would immediately go to the exhaust pipe of the nearest diesel pickup, or stand on the leeward side of the place where the coffee is roasted - yes, yes, I know how much you harm my lungs!

The device boots up in 4 seconds after pressing the button. First, it shows an erroneously high value, and then in 5 seconds it stabilizes the indicators. Most of the samples coincided with the readings from the National Sampler project, located half a block from me. The usual shocking indicators of the toaster I posted at the beginning of the article. Another video shows the result of measuring granola. She exuded small particles with a concentration of 50 ppm for more than an hour after I took it out of the oven. It happens that the "nostrils" for some time hold the smell and show a high level of particle content, so before you can quickly re-read them, you can blow them first. Two months ago, PM _2.5 particles were a serious problem, and now no one remembers them. Not to mention global warming.