So I can measure temperature... Great deal, this is described a hundred times over the web, I need also humidity. There are several humidity sensors around, but most of them are capacitive or resistive types. This kind of sensors are fine, but they have some problems. Resistive sensors need an alternate current to work, capacitive sensors fail when condensation occurs (resistive sensors also), I also couldn't find a reseller in Brazil, so I decided to use two temperature sensors in a psichrometric configuration. One sensor is wetted and both are maintained in a constant airflow. The evaporation occurring on the wetted sensor lowers the temperature and this can be used along with the dry sensor temperature to calculate the relative humidity.
This calculus also needs some other parameters like air pressure, but this is of little impact on the overall result so a fixed value according to the altitude should do... In the future I will try to include a barometric sensor.
Years ago I made some tests using this to make a higrostat and it worked fine and so it did with the Arduino. My first attempt with the Arduino gave me precise readings, but way too sensitive to little temperature variations and electromagnetic interferences. I solved this by using decoupling capacitors and some programming tricks.
After testing this configuration for several weeks, I concluded it is the best solution for my needs. It depends only on one kind of sensor, gives me temperature, humidity and dewpoint readings, and is very precise. Now I'm working on a prototype to test this in the real world. It has a LCD, three buttons to adjust the parameters, four high-power relay outputs and communicates with the computer, all in one! In the next postings I'll describe the circuit, some aspects of the Arduino programming and the use of Processing, I will put some pictures and graphs I've got simulating a cultivation room using an icebox, a heater and peltier elements. I also will describe ideas in controlling temperature vs humidity, a tricky task when it comes to get the perfect ambient for your mushrooms...
This calculus also needs some other parameters like air pressure, but this is of little impact on the overall result so a fixed value according to the altitude should do... In the future I will try to include a barometric sensor.
Years ago I made some tests using this to make a higrostat and it worked fine and so it did with the Arduino. My first attempt with the Arduino gave me precise readings, but way too sensitive to little temperature variations and electromagnetic interferences. I solved this by using decoupling capacitors and some programming tricks.
After testing this configuration for several weeks, I concluded it is the best solution for my needs. It depends only on one kind of sensor, gives me temperature, humidity and dewpoint readings, and is very precise. Now I'm working on a prototype to test this in the real world. It has a LCD, three buttons to adjust the parameters, four high-power relay outputs and communicates with the computer, all in one! In the next postings I'll describe the circuit, some aspects of the Arduino programming and the use of Processing, I will put some pictures and graphs I've got simulating a cultivation room using an icebox, a heater and peltier elements. I also will describe ideas in controlling temperature vs humidity, a tricky task when it comes to get the perfect ambient for your mushrooms...
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