Adding a simple Dew Point function to Adafruit DHT library

[TeddyMcSnuggins]

Hi. I am an astronomer/astrophotographer. I am currently building a control board for my Celestron telescope and one of the metrics I want to collect is the Dew Point. I will use this in deciding the power level I will supply to my Dew Heater on the telescope. I have found a simple Dew Point calculation, which would be great to be able to reference from a DHT sensor. The calculation can be found at https://iridl.ldeo.columbia.edu/dochelp/QA/Basic/dewpoint.html.

Would this be something that you would consider adding to the current library? I have provided my code below for your reference. This was tested on the following:

• Arduino board: *ARDUINO/UNO R3
• Arduino IDE version (found in Arduino -> About Arduino menu): 1.8.19
• Adafruit DHT11 and DHT22 sensors

DHT.h float computeDewPointSimple(float temperature, float percentHumidity, bool isFahrenheit = true);

DHT.cpp /*!

• @brief Compute Dew Point - Simple Method
• Using formula was proposed in a 2005 article by Mark G. Lawrence in the Bulletin of the American Meteorological Society:
• (https://iridl.ldeo.columbia.edu/dochelp/QA/Basic/dewpoint.html)
• @param temperature
• temperature in selected scale
• @param percentHumidity
• humidity in percent
• @param isFahrenheit
• true if fahrenheit, false if celcius

• @return float dew point */ float DHT::computeDewPointSimple(float temperature, float percentHumidity, bool isFahrenheit) {

  float hi;

  if (!isFahrenheit) temperature = convertCtoF(temperature);

  hi = temperature-((100 - percentHumidity) / 5);

  return isFahrenheit ? hi : convertFtoC(hi); }

There is a more complex function that gives greater accuracy, which is detailed on the web page provided above, but I have yet compiled that function.

Kind regards Teddy

[TeddyMcSnuggins]

Hi. I have enhanced the code to now include both the simple method documented above and the more complex, but more accurate function as well.

I have attached the revised code base for your consideration. I have renamed the files as .txt so that they are accepted by the upload facility.

Many thanks Teddy DHT.cpp.txt DHT.h.txt keywords.txt

[TeddyMcSnuggins]

Sorry, I should have added that I have tested both functions using DHT11 and DHT22 sensors, and verified the results using online Dew Point calculators.

Teddy