Sensly Hat for the Raspberry Pi Air Quality & Gas Detector V0.9

Published

Introduction: Sensly Hat for the Raspberry Pi Air Quality & Gas Detector V0.9

About: Altitude Tech LTD is founded by professionals and students in the area of robotics, electronics and product design, which makes the team the heart of the company.

Sensly is a portable pollution sensor capable of detecting the pollution levels in the air using its onboard gas sensors to collect information about the various gases present. This information can be fed directly to your smartphone for real-time push notification updates. Sensly uses industrial sensors that assure an accurate reading of the office, home, or work environment. Being aware of this data helps you to take action and bring the pollution levels down around you.

Our team at Altitude Tech LTD are big fans of the Raspberry Pi mini computer. We’re really keen to help the Raspberry Pi community develop their own Sensly device and start working on experiments whilst learning about different types of gases. We’ve developed the Sensly Hat for the Raspberry Pi. Initially launched on Kickstarter, we’re excited to provide this innovative development product to makers.

How To Use The Sensly HAT

Imagine using the Sensly Raspberry Pi HAT to:

  1. Build you own weatherproof case and monitor air quality in remote locations
  2. Monitor the air quality around your home
  3. Use it for school experiments.

Step 1: Parts in the Box

Start with getting everything you need.

  • Sensly HAT
  • BME 280 temperature, humidity and pressure sensor module
  • Sharp PM10 Sensor
  • PM10 Cable
  • 40 Pin Raspberry Pi header

Step 2: Putting Sensly All Together

Let’s put it all together:

  • Put the 40 pin header into the pin holes on the Sensly HAT then place the Sensly HAT onto the pi
  • Place the BME 280 module on to the Sensly HAT ensuring the pins match up. Look under the module to know which direction it should be facing.
  • Plug the PM Sensor Cable into the port labeled PM Header
  • Once this is done, we can power on the Raspberry Pi.
  • Due to the power draw of the Sensly Hat when fully operational it is recommended that you use a raspberry pi charger to power your pi.

Step 3: Extra Parts

Getting everything for your raspberry pi

  • Raspberry pi 2 or 3
  • Monitor
  • Keyboard and mouse
  • Internet Connection
  • HDMI Cable
  • Raspberry Pi 3 charger
  • Latest version of Raspbian Jessie

Step 4: Setting Up the Raspberry Pi

The guide to setup a raspberry pi if you need from the raspberry pi foundation

https://www.raspberrypi.org/learning/hardware-guid...

Latest version of Raspbian Jessie can be found on the link below.

https://www.raspberrypi.org/downloads/

Step 5: Download the Software

Setting up the Raspberry Pi to connect to the Sensly HAT.

There are a few ways to do this, first you can download the Raspbian image here . This will be preconfigured to work. Secondly, you can download the install script from https://github.com/Altitude-Tech/Sensly_Install

Firstly we need to download the install scripts using the command. Make sure you are in your home directory

Then we change directory to the Sensly_Install folder

  • $ cd /path/to/Sensly_Install

Next, we need to make the install script executable.

  • $ chmod u+x ./Sensly_Dev_Install.sh

Finally we run the script. There will be some prompts that you will need to type in Y to confirm you want to continue

  • $ sudo ./Sensly_Dev_Install.sh

Once completed it your pi will restart. To confirm that everything is working we can run the following command.

  • $ i2cdetect -y 1

You should be able to see positions 05 and 76 on the screen.

Step 6: Calibrate the Gas Sensors

There is a pre-heating/burn-in phase required
to remove the protective coating the sensors have when we receive them from the manufacturers, this is typically 48 hours and only has to be done once. After that, we typically recommend heating the sensor for 15 minutes to stabilize readings before logging any data.

Now we need to calibrate the Gas Sensors to be able to calculate the PPM. To do this we need to put the Sensly HAT in a clean air environment. This could be outside or if you have the facilities, in synthetic air. While the air you put it in will affect the accuracy of the sensors it will not affect precision so if you are looking to track changes in your air quality Sensly will be suitable. The Sensly HAT comes pre-loaded with the calibration firmware, so we can simply run the calibration script to find the R0 values for each Gas sensor. To be able to put Sensly in the calibration environment we need to be able to run the calibration script when the Pi boots up. For this, we will need to download:

  • $ git clone https://github.com/Altitude-Tech/Sensly

Inside that folder, we will use the Sensly_Calibration.py Script, but first we need to set up the automatic calibration. Type into the terminal the following commands

  • $sudo crontab –e

If you have never run crontab before then you will need to choose which editor that you want to use to edit it with, I normally use nano so I pick option 2. Next, we need to put the following command into the file

  • $ @reboot sudo python /path/to/Sensly_Calibration.py

Then we close the file using Ctrl+x then Y. This will mean every time you start up your Pi it will run the calibration script.

You can now take it to you clean air environment and leave it for between half an hour, to an hour. The longer the better.

Once this is finished you should have a file named Sensly_Calibration_"date"_"time".csv where "date" will be replaced with the current date stored on the Raspberry pi and "time" is replaced with the current time. This file will contain the R0 values calculated during the calibration phase averaged every 5 minutes. Since the script logs a running average, you take the last entry in the file as the R0 values for the MQ2, MQ7 and MQ135. This will then be put into the Sensly.py file. to enable us to calculate the PPM values for each gas detected

Step 7: Running the Sensly HAT

To be able to run Sensly in full operation mode we need to update the firmware to get it out of Calibration mode. This is done by running the update.sh script

  • $ cd /path/to/Sensly_Install/
  • $ sudo ./Update.sh

Once completed we can now run our main python script. Inside the Sensly folder run:

  • $ python /path/to/Sensly.py

Finally, to enable you to run the script automatically we then run the crontab command again.

  • $ crontab -e

Then add this to the end of the file while removing our earlier entry

  • $@reboot python /path/to/Sensly.py

Now every time you boot your pi the Sensly HAT should be logging data to a csv file. The final step is to take the R0 values you obtained during the calibration step and put them in the highlighted the last screen shot.

The next instructable we will be releasing will show you how to link this up with plotly.

Step 8: Final Steps

Please share your data as it will help us build better updates for Sensly.

If you think you have the skills to write a great Instructable using Sensly then purchase one from our store and if we like it we will refund your money and even send you more goodies!

3 People Made This Project!

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Tips

Questions

Hi, I purchased your form and I'm trying to get it to work, but I stop at the calibration script. I can not start the script update and that for operational boot of hat (sensly, py) What should I check to understand my error?

./Sensly/Sensly.py:110: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings.

GPIO.setup(23, GPIO.OUT)

2018-05-14 10:40:34.576 DEBUG Sensly - init_BME280_Sensor: ----- BME Sensor {}

2018-05-14 10:40:34.578 INFO Sensly - <module>: You can check your data into ./sampleData/Sensly_%d-%m-%Y_%H_%M_%S.csv

Traceback (most recent call last):

File "./Sensly/Sensly.py", line 527, in <module>

init_BME280_Sensor()

File "./Sensly/Sensly.py", line 105, in init_BME280_Sensor

bME280_Sensor = Adafruit_BME280.BME280(t_mode=Adafruit_BME280.BME280_OSAMPLE_8, h_mode=Adafruit_BME280.BME280_OSAMPLE_8, address=0x76) # Sometimes Crash with a connection timeout

File "/home/pi/Sensly/Adafruit_BME280.py", line 127, in __init__

import Adafruit_GPIO.I2C as I2C

ImportError: No module named Adafruit_GPIO.I2C

or

Enable_bootloader.py:5: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings.

GPIO.setup(23, GPIO.OUT) ## Set up GPIO Pin 4 to output

Bootloader version 31

Chip id: 0x444 (Unknown)

Traceback (most recent call last):

File "stm32loader.py", line 450, in <module>

cmd.cmdEraseMemory()

File "stm32loader.py", line 210, in cmdEraseMemory

return cmd.cmdExtendedEraseMemory()

File "stm32loader.py", line 240, in cmdExtendedEraseMemory

self.sp.timeout = 30

File "/usr/lib/python2.7/dist-packages/serial/serialutil.py", line 352, in timeout

self._reconfigure_port()

File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 427, in _reconfigure_port

[iflag, oflag, cflag, lflag, ispeed, ospeed, cc])

termios.error: (22, 'Invalid argument')

30 Comments

Hello.
I don't know why but all written data values to zero.
Do you find how to do to resolve this problem ?

All written data values to Zero.PNG

Still having problems even after I installed the stuff from your GitHub

Made a fix for calibration and working on the rest, checkout for the branch on gitHub

https://github.com/Altitude-Tech/Sensly/tree/gpio_calibration_fix

Hi

I'm struggling with this hat

I'm using a pi zero W last raspbian image

non of the python is working

neither Update.sh or Sensly.py or calibration are not collocting any data

is there any specific options to do ?

root@raspberrypi:/home/pi/Sensly_Install# BOOT0=1

root@raspberrypi:/home/pi/Sensly_Install# ./Update.sh

Traceback (most recent call last):

File "stm32loader.py", line 427, in <module>

cmd.open(conf['port'], conf['baud'])

File "stm32loader.py", line 71, in open

timeout=5 # set a timeout value, None for waiting forever

File "/usr/local/lib/python2.7/dist-packages/serial/serialutil.py", line 240, in __init__

self.open()

File "/usr/local/lib/python2.7/dist-packages/serial/serialposix.py", line 272, in open

self._reconfigure_port(force_update=True)

File "/usr/local/lib/python2.7/dist-packages/serial/serialposix.py", line 438, in _reconfigure_port

[iflag, oflag, cflag, lflag, ispeed, ospeed, cc])

termios.error: (22, 'Invalid argument')

^CCan't init. Ensure that BOOT0 is enabled and reset device

^C^CTraceback (most recent call last):

File "stm32loader.py", line 474, in <module>

cmd.releaseChip()

File "stm32loader.py", line 110, in releaseChip

self.reset()

File "stm32loader.py", line 98, in reset

time.sleep(0.5)

KeyboardInterrupt

Everything installed. Got through Kernel Panic issue. i2cdetect looks good. Now Update.sh (Can't init), Sensly.py (Heating completed > Remote I/O error), and Sensly_Calibration.py (Remote I/O error) errors out. Anyone got any suggestions?

1 reply

Hi there, how did you overcome the kernel panic issue?

I ran the installer script from GitHub and it's now trashed my Pi 3. Kernel panic on every boot. The link to your pre-configured image doesn't seem to work either. Please advise.

I ordered a Sensly Hat 2 weeks ago for this instructable. Order is still "processing" and the company is not responding to emails or calls.

Well, I also got a Kernel Panic on a RPi3+Raspbian OS. My bad that I didn't save my SD image before trying, but I thought this would be just a simple install without killing my rpi OS. Really sad about that.

This totally worked fine before running the sensly_dev_install.sh, I had my postgres server running there for weeks without an issue. I use win32diskimager to write the image.

Any way to recover from this easily? I'm trying to do that just now, but I have a feeling that sd is gone in heaven.

IMAG0205.jpg
6 replies

I just went ahead and downloaded the image and went on with the steps. calibration is not running on reboot even though I added the line and exchanged the path to the correct path. But ran that manually and seemed to atleast work that way. Now running update.py is giving the following output:

~/Sensly_Install $ sudo ./Update.sh
Bootloader version 31
Chip id: 0x444 (Unknown)
Extended erase (0x44), this can take ten seconds or more
Traceback (most recent call last):
File "stm32loader.py", line 450, in <module>
cmd.cmdEraseMemory()
File "stm32loader.py", line 210, in cmdEraseMemory
return cmd.cmdExtendedEraseMemory()
File "stm32loader.py", line 242, in cmdExtendedEraseMemory
self._wait_for_ask("0x44 erasing failed")
File "stm32loader.py", line 80, in _wait_for_ask
raise CmdException("Can't read port or timeout")
__main__.CmdException: Can't read port or timeout

Did you guys ever test the code you released? Crashing OSes and consumers constantly hitting walls is not something you want as an end product.

Went ahead and ran the script anyways, it created the new .csv file, all readings are 0,0,0,0,0,0,0,0 for every 30 seconds for the past 20 minutes.

Now I must really ask is this hardware really works?

UPDATE: After recalibration it seems to measure MethanePPM, but everything else is still 0.

The Kernel panic may have been caused by the apt-get update, upgrade and dist-upgrade commands, the reason we add this to the script is to make sure the raspberry pi is at the latest version. This is to ensure that the raspberry pi is a close to our in lab test conditions as we cannot guarantee that the install will work on earlier versions. We are sorry that you have had these issues. There is a potential to recover your information by plugging your SD card into a computer running a linux os.

In response to your second comment, would it be possible to screen shot the path you save it to and the file explorer view of the file location by opening a separate terminal and using the command scrot -s then clicking on the window you want to screen shot. This will help us find the issue.

In terms of the update.py not working it seems like the program or the board is hanging could you please try restarting the entire system and try again. If this doesn’t work could you tell me which raspberry pi you are using?

Finally in terms of the output my first question would be where you did calibrate the sensors? Also I think I should point out that majority of the gases detected with the exception of CO2 shouldn’t be picked up normally if they are it would mean your home is has dangerous gases. If you would like to test the response of the sensors, you can you lighter gas to ensure that the sensor are responsive

Hope this help and sorry for the delayed response

I'm pretty sure the updater caused it yes. But nonetheless it was your install script running it :)

The calibration mostly worked after a few reboots, I still have an issue that if the code runs for a while even if it had values instead of 0 after a 20minutes it goes wild and all becomes 0. I however had to modify your script to make it work with our script and as I converted some code, I noticed the reason is that after a few (didn't count them, I would say around 10-20) queries (in my script I query every seconds instead of 30 seconds) the SenselyHAT is just not responding and throws an IOError on sensor reading and to me it seems until the pi is restarted it won't be able to connect to it. I don't know though that the fact that the package arrived with the 40 pin gpio bent or something else causing it. Other than plugging the parts together was hard didn't seem to matter that much in the workings of the device.

As to the measured gases I honestly don't know which and how much should be in my air. I understand that it is normal that the values are 0, I was just hoping for something (which later came in a single cell having values) It just seems crazy to me that the air in the city I live in has 0 dangerous gases. I'm happy to hear that that's normal.

I haven't ran the sensely.py lately, but with the basically same code I did for my script, it seems to me that measurements are being made though. I'll attach a shot of the table I have. there is a part where the data just died after running the code, then when I restarted the pi it worked again. it's in a 'safe' place without movement so I doubt disconnection could have happened, however the cabled attachment unit falls apart really-really easily for me, but I always check that it's plugged together when I leave the unit to measure.

Any help would be appreciated regarding this, since this is the last thing that seems to be nagging me.

data.PNG

Wow you guys are not quick at all. Anyways the device is now totally not responding to anything. I get IOError tried rebooting it multiple times but nothing.

Traceback (most recent call last):

File "/home/pi/Sensly/Sensly.py", line 80, in <module>

sensor = BME280(mode=BME280_OSAMPLE_8)

File "/home/pi/Sensly/bme_combo.py", line 114, in __init__

self._load_calibration()

File "/home/pi/Sensly/bme_combo.py", line 119, in _load_calibration

cal1 = self._device.read_i2c_block_data(BME280_I2CADDR, 0x88, 24)

IOError: [Errno 110] Connection timed out

This is the error I get now, 2 weeks ago it was only coming on just after a few queries now it's not even doing anything... Is there a way to connect more quickly with you guys since a monthly response is not good when the device is faulty. Seems like it's a waste of money at the moment.

Both of the instructables for Sensly I am having issues with the crontab step. I follow the instructions to add the commands to run the calibration or the Plotly python script at reboot but neither one is working. What am I doing wrong? I am using the Sensly.img that was provided.

Hi there, I want more information on ordering the Sensly Hat, I sent an email to the email id provided on the website and I also tried calling the phone number but have not received a reply. I would need 4-5 hats.

Since calibration did not lead to sensible values, I tried to analyze the code to find some values which generate at least some relative curves. I send the data to IBM Watson IoT to draw the charts. Below image shows basically the CO2 curve. At 17:30 I entered the room, which means, it measures 'something'. I wonder where these periodic spikes come from. Is this the heating cycle of the sensor? Any chance to remove this (other than using a 30 min average)?
The MQ7 sensor seems to be completely unusable. The value chances periodically with factor 10000. Anything I missed?

Bildschirmfoto 2017-01-30 um 17.47.56.png
1 reply

Hi Frank, Sorry for the delayed reply.

The reason for this is that the MQ7 requires a special heating cycle to detect Carbon Monoxide. This cycle is 60 seconds at 1.4V and 90 seconds at 5V. The Sensor is ready to be read during the 5V stage so to prevent it being read during the 1.4V stage we set the value it outputs during this stage to a number that would not give any ppm reading. This is why you get those very high rs/r0 values on the MQ7. Could you please let me know in what envrionment you calibrated the Sensors in?