projects/mq135lib
6
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

docs

Browse source
This commit is contained in:
GrafZeppelin 2021-04-12 21:22:12 +02:00
parent 15e780e6e9
commit 3d7ed81e6e
1 changed files with 34 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

37
README.md
View file

@ -3,12 +3,43 @@
Arduino Library for MQ135 Sensor
## Learn more
* [https://jayconsystems.com/blog/understanding-a-gas-sensor]()
* [https://jayconsystems.com/blog/understanding-a-gas-sensor](https://jayconsystems.com/blog/understanding-a-gas-sensor)
Basic understanding of an Air-Quality Sensor
* [https://github.com/miguel5612/MQSensorsLib]()
* [https://github.com/miguel5612/MQSensorsLib](https://github.com/miguel5612/MQSensorsLib)
Another MQ135 Library
* [https://github.com/GeorgK/MQ135]()
* [https://github.com/GeorgK/MQ135](https://github.com/GeorgK/MQ135)
Another MQ135 Library
## How does this work?
First we need to calculate the actual voltage from our sensor. The value we read by ``analogRead`` is just a value mapped to 2^10 bits.
Since we are running our sensor at 5V, a measured value of 1023 equals 5V and the measured value 0 equals 0V. We convert this with the following formula:
```
// x is our measured value
voltage = x * 5 / 1023
// or
voltage = 5x / 1023
```
Next we can calculate the resistance of the sensor.
For more details should be looked up in this article: [https://jayconsystems.com/blog/understanding-a-gas-sensor]()
```
V = I x R
VRL = [VC / (RS + RL)] x RL
VRL = (VC x RL) / (RS + RL)
So now we solve for RS:
VRL x (RS + RL) = VC x RL
(VRL x RS) + (VRL x RL) = VC x RL
(VRL x RS) = (VC x RL) - (VRL x RL)
RS = [(VC x RL) - (VRL x RL)] / VRL
RS = [(VC x RL) / VRL] - RL
```
To calculate the gas content in the air from the resistance we use the values from [https://github.com/miguel5612/MQSensorsLib](https://github.com/miguel5612/MQSensorsLib)