Hey! I'm up to start a Arduino project, and my goal is the make an auto watering system for my greenhouse. My plan is to have some sort of solar cells/panel on the roof of greenhouse connected to a battery, either directly or through the Arduino. Then from the Arduino to a water regulator that should regulate the water fluid depending of the humidity sensor and the temp. sensor. The water will come either from a water tank or directly from the water tap. Hope you understand.
Please check my attached image for more details.
My questions are:
Is this project possible?
How to prevent battery to overcharge?
Do you guys have any advices on Arduino components to use, like "motherboard" and so on?
That is a straightforward project but has a number of components that have nothing to do with Arduino. If you are a beginner, it will be quite challenging.
Any Arduino would be powerful enough to control the system.
A commercial PV array, deep cycle battery and suitable battery charger should be purchased.
You will need to research humidity and temperature sensors, pumps and pump controllers and learn how to use them. There are a number of similar projects posted on the web that should provide helpful information.
Thanks for a fast answers! Aside from the Arduino board the components(found on ebay) I want is a ph-sensor, temperature and humidity sensor, Water regulator (also found on ebay).
If I connect the "Arduino Water Regulator" directly to the "water tap" do I need to have a pump then?
Ah many thanks! And then I can tell the valve from the Arduino what to do and get the electricity from the Solar cells instead of an usual AC Adapter? Does the system have enough power then to operate the electricity water valve and let the water go? I may need enough solar panels to get ~12V, I would think these valves are 12V.
Well, as long as the valves use little to no energy whilst shut.
I had a small 10W solar panel powering an nano. It did not last long...a 12Ah battery drained slowly in winter over a few weeks. (0.1A ish...247 = A good 16.8Ah. In winter, a 10W panel here in the UK barely puts anything out...less than what my load was so the battery slowly drained.
I now have a 260W panel that even now on an overcast day puts out 400mA (about 5W). This is enough to keep a nice 100Ah lead acid topped up. I may even attach a PWM heater pad to keep seedlings nice and cosy (pulls maybe 10W at 50% PWM...only on when drops below 3 degrees).
So basically, depending where you live, you may need more than you would expect.
Thanks! I will only use the system in the spring/summer in my greenhouse. In the autumn and winter I will put the stuff in my garage. The water valve says it current use: 250mA which is ~0.25W. Let's say I just have a small solar cell with about 1.5W and made for 12V. I will probably have a better one but just as an example.This should not be a problem then? However the only problem will be that the battery takes long time to charge.
With such a small panel, maybe using just a zener diode to protect a battery may be a better option. It uses far less current as charging circuits need to use some current themselves to monitor!
A 13V zener diode will keep a small 12V lead acid battery topped up maybe.
Okey nice! Then I can buy what solar panels I want for the project with enough Watt? Because I found one that are usually used for charging 12V car batteries with around 100W. It has two crocodile clips but I may then just cut them off and plug into my solar cell controller instead?
You first need to decide how to put together your watering controller.
After you've found suitable valves and sensors and have everything working with a AC-powered supply, measure the current requirements. Then you can pick a battery and solar panel.
Well, I found this Water Valve 12V(normally closed) that I think I should use. Sensors and so on are no problem I think, found components that fits together, that includes the Arduino UNO mainboard.
Hey again, is this possible as I have drawn(see my attachment) or is it "just" to program the Arduino not to let electricity out to the valve if the time isn't correct?
For ex. I just want the water to be on for like 3 minutes per day at 6pm to 6:03pm for example. Is this possible just through programming, I've also thought about some sort of extern timer to wake the Arduino up if I put it into Sleep mode during the day when it's not supposed to be on(Watering).
One other thing is that the Water Valve consumes ~300mA but in the description of the Arduino UNO board it says: "Can supply 40 mA of DC current per pin" this made me a little bit worry. Won't it work then?
"Can supply 40 mA of DC current per pin" this made me a little bit worry.
Actually, you do not want to go over 20 mA. Never attempt to power a relay or a motor from an Arduino.
You need a driver for the relay, as shown in reply #16. Use a 220 Ohm (at least) resistor in the base of the transistor -- shown as a small oblong box in the drawing.
any other advices for this then? 
