Humidor Maintainer

I have an Arduino Diecimila and I am looking to undertake a (hopefully) simple project with my Arduino. I was given this Arduino by a buddy of mine who never used it but he figured I might. I've had it laying around for a few months, and have not done much with it. I have done some very simple operations with it because, along with the board, he gave me a load of motors, resistors, LEDs, etc. About as far as I've gotten is to make it blink and also to fade.

What I would like to do is to set up the Arduino to add water to a cigar humidor I have, roughly every 3 weeks. I know, certainly not using the Arduino to its full potential, but still something I think would be cool. I already have some plans drawn up as far as the mechanics of how it will function, as well as an idea of what I need. It seems that I will need a solenoid valve that will connect to the Arduino, and program that much like a blinking LED; set a program to open the valve for 5 seconds, then delay for 3 weeks and do it again.

What I really need help on is finding the right solenoid valve, keeping in mind that my plan involves a gravity-fed water supply, and also, how to connect a solenoid valve to my Arduino? I'm assuming that there will be some voltage issues possibly, but really have no idea on that.

Thanks in advance for the help

You could also measure the humidity: Arduino Playground - HomePage

The valve should be suitable for water. Perhaps a 12V solenoid valve. Do you have a 12V power supply ?
Some solenoid valves use a membrane, which uses the pressure to open and close. You don't have enough pressure for that, so you need a direct acting valve.
On Ebay there are big round valves like that, but most of them require a large current. I bought one which needs 1.4A, but there are others which need less current. Search Ebay for "2W025", look for one which has the current in the description. They are big and sturdy and will do the job. And you only need to activate them for a short time. They come with different connections, so you must know what type of connection you want. You also need some tubing/adapters and so.

Connecting it to the arduino requires a transistor (and a resistor to the base) or a mosfet.
You also need a flyback diode over the solenoid valve.

There might be a problem with calcification of the solenoid valve... So choosing a big sturdy solenoid valve is not such a bad idea.

Links:

http://mural.uv.es/jocasa/dripping/dripping.html

Consider a clock (RTC) too. Unless your power is unusually reliable, you'll need one to avoid pumping water into the humidor too early or late after the Arduino restarts in an outage.

wildbill:
Consider a clock (RTC) too. Unless your power is unusually reliable, you'll need one to avoid pumping water into the humidor too early or late after the Arduino restarts in an outage.

Another option is to get a Humidity sensor as mentioned above and then forgo the time delay all together. Just add water whenever the humidity drops below a certain level.