Hello, I would like to jump quickly into mushroom growing but am really lost. I would like to spend about 40 USD (more if needed) on humidity and temperature control. Could you please recommend me list of all the hardware required (all the heater and humidifier inputs and outputs, relays etc?)? I found list of supported HW on Github, but am not sure, which parts to choose.
Thanks very much in advance, every bit helps.
For a simple setup to regulate temperature and humidity, you'll need:
~$50 Raspberry Pi, micro SD card, power supply
~$10 - $20 Humidity/Temperature sensor. The AM2315, BME280, and HTU21D are great options. The AM2315 comes with wire, a porous case, and a mount. Bare sensors require a bit more work to put into use.
~$20 - $30 Humidifier
$? AC or heater
From there, you can think about what kind of relays you want to use to control your temperature modulating devices (heater, AC, etc.) and humidifier. There are pre-built control boxes that connect right to the Raspberry Pi to switch outlets that these devices plug into for power, but a pre-built system is usually going to be more expensive than building it yourself. I would check out my mushroom cultivation articles in my Projects section of this site to see how to wire up relays to mains electricity, which will allow you to build exactly what you need for you particular application.
Note that for fast-switching systems, like humidity and temperature regulation, where the relay may rapidly switch several times per minute, you'll want to use solid state relays to extend the life and not be driven mad by the constant clicking you would hear from mechanical relays. For applications that require less switching, like fans that only come on every few hours, mechanical relays are fine.
I generally recommend the Sainsmart relay modules for beginners. They come in 1, 2, 4, and 8 relay configurations and with either mechanical or solid state relays. I'll typically use a 2-channel solid state module with a 2-channel mechanical module in one power box I make to control 4 outlets for a simple project or if I'm experimenting. This gives me options for the switching frequency and the amount of power I can switch (their solid state relays max at 2 Amps and their mechanical relays max at 10 Amps). If I need more control, I make a larger control box (see my mushroom cultivation articles in the Projects link, above).
Hope that helps with your research. If you have any other questions, feel free to ask.
Thank you very much for quick response!
I am still kinda confused about the heater - do I get it right that I have to find some space heater (that will be standing next to mushrooms box) that is Raspberry compatible and will be PID controlled to keep the box warm enough?
You'll have to determine how much heat you'll potentially need. For example, I've used a 1500 Watt heater to heat a 20-foot shipping container and a 150 Watt heater to heat small plastic containers. These ideally would go inside the chamber to be heated and have the airflow circulating to homogenize the air temperature, but you could also heat the air surrounding the chamber if your system allows that possibility. Keep in mind the second heater requires DC voltage, not AC like the first heater. This means although mechanical relays could switch the power, solid state relays will need to be designed for DC for it to work with them. This is why designing for only AC is often easier, as you can create a power control box that uses AC and if all your devices use AC, everything is compatible. Another option with the second heater is to control the power to the AC-to-12-volt-DC adapter that powers the heater.
These heaters would interface with the Raspberry Pi by having the signal wire of the relay connected to a GPIO of the Pi. Mycodo would then use the sensor measurements as input to a PID controller that would then modulate the relay until the measured temperature approaches the desired temperature.