Confused because coding/annotations do not match

[schlaubstar]

Hi ... at first a great thank you for your work but I'm confused with your code.

You always say for your function:
/****************** MQResistanceCalculation **************************************** Input: raw_adc - raw value read from adc, which represents the voltage....

but when it gets called e.g. by MQCalibration you only pass the value of analogRead(mq_pin) as raw_adc like here ..

float MQCalibration(int mq_pin) { ..... for (i=0;i<CALIBARAION_SAMPLE_TIMES;i++) { //take multiple samples RS_AIR_val += MQResistanceCalculation(analogRead(mq_pin)); ..... }

For my understanding analogRead will return a value between 0 an 1023 indicating "units" of voltage.
To convert those to the voltage representation you would actually have to do something like multiplying it with the voltage of your device - in most cases when using MQ-x Sensors, youll go with a 5V arduino so it should be:

MQResistanceCalculation(analogRead(mq_pin) * 5.0 / 1023.0);

or am I wrong ?

[mdsiraj1992]

"MQResistanceCalculation(analogRead(mq_pin) * 5.0 / 1023.0);"

This exact same thing is being done by the MQResistanceCalculation function used in the code in a different way
`float MQResistanceCalculation(int raw_adc)
{
return ( ((float)RL_VALUE_MQ135*(1023-raw_adc)/raw_adc));
}

Watch this video(https://www.youtube.com/watch?v=bL0cySlLlYo&index=1&list=PLwc7ohfhglpty1sZS0iTDxsNQ-CIaeR1X) maybe you will understand it (don't worry about the language in the video, even i don;t know it)
`