Arduino - controlling fans and door/hatch greenhouse

Frode,

          yes you can do all you want to do for your greenhouse and in fact I do all of those things in my greenhouse.  However I feel obliged to issue the usual advice regarding the 220 volt stuff, which is unless you are completely competent to work safely with such voltages you should not attempt projects involving mains electricity especially where there is likely to be water / moisture.

At a safer level say 12 volt then you can definitely control low voltage lights, vent openers, fans and a watering system.

For vents you need some form of motorized mechanism to move the vent, the mechanism depends on how much you need the vent to open and its weight. Alternatively a bank of low voltage fans can provide air movement.

For my watering system I use 12 volt solenoid valves, one per plant.  Not cheap initially but very versatile.  Alternatively one valve can control several 'drippers'.

I do use soil heating cables on my propagating benches.  These come prewired and in my case the supply cable goes into a sealed box which houses the control relay in a separate dry area.  The opto isolated control relay is controlled by an Arduino which senses temperature, humidity and ambient light level.  The DHT22 does both temperature and humidity, the BH1750 is the ambient light sensor.  The Dallas 18B20 is also an excellent temperature sensor.

Stealing a phrase from another contributor 'Google is your friend' and my advice to you is to google each of the items you want to do and develop each aspect on its own then add it to your complete system.  All of the sensors I have mentioned have some good information on the net and often Arduino example code and libraries.

Frode,

          yes you can do all you want to do for your greenhouse and in fact I do all of those things in my greenhouse.  However I feel obliged to issue the usual advice regarding the 220 volt stuff, which is unless you are completely competent to work safely with such voltages you should not attempt projects involving mains electricity especially where there is likely to be water / moisture.

At a safer level say 12 volt then you can definitely control low voltage lights, vent openers, fans and a watering system.

For vents you need some form of motorized mechanism to move the vent, the mechanism depends on how much you need the vent to open and its weight. Alternatively a bank of low voltage fans can provide air movement.

For my watering system I use 12 volt solenoid valves, one per plant.  Not cheap initially but very versatile.  Alternatively one valve can control several 'drippers'.

I do use soil heating cables on my propagating benches.  These come prewired and in my case the supply cable goes into a sealed box which houses the control relay in a separate dry area.  The opto isolated control relay is controlled by an Arduino which senses temperature, humidity and ambient light level.  The DHT22 does both temperature and humidity, the BH1750 is the ambient light sensor.  The Dallas 18B20 is also an excellent temperature sensor.

Stealing a phrase from another contributor 'Google is your friend' and my advice to you is to google each of the items you want to do and develop each aspect on its own then add it to your complete system.  All of the sensors I have mentioned have some good information on the net and often Arduino example code and libraries.