Last time we updated our simple SMOG sensor with display (OLED) and added BME 280 to verify the SMOG measurements – the environmental sensor – as we know that humidity over 70% can add up to the SMOG.
It’s time now to protect our sensor.
Why do we need sensor protection?
Smog sensor – it’s laser in particular – has a limited lifetime – datasheet states 8000 hours. Both the fan and the laser diode should not work continuously – because of wear and tear and also – it clogs the senor with dust. The idea is to only turn it on when it is really needed – for the time of measurement.
Of course SDS011 supports sleep mode – “software off”, and this is obviously the best and natural way to protect it. I decided not to use it because it is not yet available in ESP Easy 2.0-dev-12, and also because the relay gives us the possibility of turning on an additional element – the inlet air heater, to avoid measuring errors with humidity> 70%, a idea for future extension of the project.
What new things will you need ?
- working SMOG sensor from previous entry, the SDS011
- A relay – this example features dedicated relay for the Wemos D1 mini, since it reduces the number of connections and saves space. And because I just had it lying around, but it can be any relay activated high status 3.3V and powered 5V.
- additional red and
- ESP Easy – already installed in previous step on the ESP8266 which is needed to control our SDS011 sensor
Let’s do it!
Connect anew all the wires – use the schema and pictures. We already know the drill – VCC power on red cables, blue – GND. The new part is the relay.
We connect in accordance with the diagram – please do mind that we change the pins, because of the Wemos D1 Relay shield. CAUTION – do not connect the power supply (+5V) until you make software changes to ESP Easy (below)
New version – our monster grows bigger!
Since we have an additional element that consumes electricity – let’s see how much mA will we need to power the solution:
We can see maximum of 200mA when all elements are active and data is sent over WiFi network. Also – 50mA when relay and SDS011 are off and ESP does not send any data.
Now – let’s move to software – the needed changes in ESPEasy configuration:
- We have to change the pins used to communicate with the I2C bus to D6 and D7, and set the low state at the boot – to make sure the relay is not powered (just in case)
- Turn on the Rules in Tools -> Advanced
- Next – change the GPIO port of our sensor to GPIO-15 (D8) – as in the connection diagram:
- We will remove the information about PM2,5 and PM10 from the SSD1306, but don’t worry – this is just temporary we will still display this data, but in a different way
Time to use new functionality – Rules on ESP Easy. Rules are the way to perform actions, and we can do it in loops. They might also depend on different parameters. We will use them to:
- switch the sensor on after 30 seconds counting from the boot of ESP8266
- Have it running for 120 seconds…
- After 120 seconds – record the data – send them to already known to you Domoticza and InfluxDB/Grafanie for presentation and graphs
- Update the OLED screen
- Wait 720 seconds (12 minutes) and repeat
How? Just paste the script into rules Rules:
On System#Boot do //This will happen at boot ESP8266 timerSet,1,30 //Set and start timer 1 at 30 seconds endon On Rules#Timer=1 do //When the timer 1 is up: GPIO,5,1 //Turn on SDS011 timerSet,2,120 //Wait 120 seconds to spin it up endon On Rules#Timer=2 do //When the timer 2 is up SendToHTTP 10.20.30.40,8080,/json.htm?type=command¶m=udevice&idx=11&nvalue=0&svalue=[SDS011#PM25] //Send the PM2,5 data to Domoticz SendToHTTP 10.20.30.40,8080,/json.htm?type=command¶m=udevice&idx=12&nvalue=0&svalue=[SDS011#PM10] ////Send the PM10 data to Domoticz OLED,2,1,PM2.5: [SDS011#PM25] //Update OLED with PM2,5 OLED,3,1,PM10: [SDS011#PM10] //Update OLED with PM10 GPIO,5,0 //Turn off SDS011 timerSet,1,720 //Set the next cycle at 720 seconds endon
This is how it looks (comments in Polish from older screenshot):
Note that the script lines will display the measured values on the OLED screen – only the ones that will be measured (otherwise when SDS011 is switched off – we would see ‘nan’ values).
Now create in Domoticz (Check out the the “dummy sensor creation” sensor entry) virtual sensors – separately for PM 2.5 and PM 10. Use the “Custom sensor” from drop-down list. The Rules scripts assumes the IDX values of 11 and 12 – change it to yours, just as the IP address and port of the domoricz.
Power on our sensor and observe the first data after around 16 minutes of running:
The final move is to configure data connection from Domoticz InfluxDB and Grafana. Another option is to send the BME280 data – and I suggest to do it every 5 minutes. Our sensor is ready!