CO sensor - TomBric/stratux-radar-display GitHub Wiki
CO (carbon monoxid) is a dangerous gas, especially in airplanes where it may enter the cockpit. I equipped the stratux display software with a sensor, which is able to detect 1 to 1000 ppm of CO. According to FAA rules a concentration of more than 50 ppm for 5 minutes should be alerted.
I used the MICS-5524 sensor to detect CO and other critical gases in the cockpit. The sensor is mounted into the 3D-printed front of the display (in this case the epaper-version). The sensor is connected to an analogue-digital converter ADS1115 and then connected to the GPIO input. Overall the additional hardware is around 15 Euros from a cheap source.
Warning/Remark:
The sensitivity of the CO-sensor has not been certified! So the values displayed may not be correct especially not in your installation environment. I tested the sensor and adjusted the values as good as possible. Take displayed CO-values as an indication only!
List of materials for the CO-sensor addition:
- ADS1115 ADC breakout board, multiple sources, e.g. Berrybase
- Adafruit MICS-5524 breakout board, multiple sources, e.g. from China
Connections from ADS1115 to PI zero 2:
| Cable on ADS1115 | Connection Point on Pi |
|---|---|
| SDA | PIN #3 on GPIO |
| VDD + 5V | PIN #4 on GPIO |
| SCL | PIN #5 on GPIO |
| GND | PIN #6 on GPIO |
| Addr | PIN #9 (GND) on GPIO |
Connections from MICS-5524 breakout sensor to ADS1115:
| Cable on MICS-5524 breakout | Connection Point at ADS1115 |
|---|---|
| +5V | VDD on ADS1115 |
| GND | GND on ADS1115 |
| A0 | A0 on ADS1115 |
CO Warner Software
The stratux display has an additional mode which shows the current CO values as well as the values in the last hour of operation. So you can see peaks in the CO level. Additionally, also in the standard radar-mode CO-alarms will be displayed on the screen. CO-alarms will also be announced via audio (bluetooth or audio out). Currently, the following alarm levels are implemented:
Alarmlevels:
| Level | Condition |
|---|---|
| 0 | no co alarm |
| 1 | 50 ppm CO for more than 5 mins |
| 2 | 70 ppm CO for more than 3 mins |
| 3 | 100 ppm CO for more than 2 mins |
| 4 | 300 ppm CO for more than 1 min |
| 5 | 400 ppm CO for more than 30 seconds |
Sensor calibration
Every sensor is a little different, so you should calibrate your sensor. According to MICS-5524 datasheet please do the calibration after 24 hours of sensor operation. Put the sensor in fresh air and press "calibrate" in CO-mode. The software will take samples for 15 seconds and take this now as 1 ppm (the value of R0 resistance should be around 300-600 KOhms). The calibration value will be stored on the device, so you need to do it only once, but of course you can repeat it.