RobTillaart
commented
4 years ago HI, long time no see ,
Yeah, played a lot with different ideas to make things easier for the users. Storing the values internally as an integer is one of them. It saves 2 bytes RAM for humidity , 2 bytes RAM for temperature and 2x3 bytes for the offsets. It adds four multiplications to be able to return floats, but it would remove some float math in the read function so that compensates. Eight boolean flags can be stuffed into one byte so that could save a few bytes but the lib only has one boolean flag left. So in the end 10 bytes of RAM would be saved. Did not spend time implementing it yet.
My temp is borderline 23-24°C so it bounces between these two like crazy on my graphs so I was checking to see if decimals where an option as a reply from the sensors.
What you could do is add a low pass filter. I give an example in simplified code
float lowPassTemp;
const float alphs = 1.0 / 3; // any value between 0.001 and 0.999 will do.
setup()
{
lowPassTemp = sensor.getTemperature();
}
loop()
{
float currentTemp = sensor.getTemperature();
lowPassTemp = lowPassTemp + (currentTemp - lowPassTemp ) * alpha; // << the trick
Serial.print(currentTemp, 2);
Serial.print("\t");
Serial.println(lowPassTemp, 2);
}The idea is that you do not replace the old temperature with the new measurement but make a step in between those two values. How much in between depends on the value of alpha. If it has the value 0 the temperature will not change at all, if it has the value 1 it will replace the old temperature completely. Another way to write it is more clear for user (uses more math)
lowPassTemp = (1 - alpha) * lowPassTemp + alpha * currentTemp;Please note that measurements will be smoother but the system will also react a bit slower to variations. You need to check what value alpha feels acceptable for you / your customer.
In a project I made it user configurable.
alpha = 0.01 + analogRead(A0) / 1024.0;so the customer could tune it with a potentiometer.
In the above alpha is a constant but you can make alpha a variable that depends on other parameters. E.g. if delta T is large make alpha also larger to follow large changes faster but stay smooth when delta T is small. Or you can make alpha depends on light conditions or UV radiation, you name it. Anything can make sense.
Enough said, please give it a try.
Mr-HaleYa
Hey Rob, Didn't you say that one of the DHTs gave a .1 number but you had float disable to save space or something like that? I don't know if that made any sense. Basically I wanted to know if the library can (or has any plans to) give float values back (or make that an option like another flag?) My temp is borderline 23-24°C so it bounces between these two like crazy on my graphs so I was checking to see if decimals where an option as a reply from the sensors.