Id like to set up a mister for my greenhouse that is controlled by a humidity sensor. Using Arduino may be over kill but I'd like to try it. I have very little experience with building circuits but can read a basic diagram and know which end of the soldering iron to hold (most of the time). Could anyone supply or point me too a comprehensive how-to that I can use for this project? I'm not even sure what parts to gather other than the plumbing, solenoid, sensor, and Arduino board. What I want to end up with is a circuit that opens a valve when the RH falls below a certain value (and then closes when the RH rises to a target). Thanks for any assistance.
Any additional hardware, if any, will be determined by the humidity sensor you use and the solenoid you use. If i'm not mistaking it will be the power requirements of those components that will be the issue. Chances are the humidity sensor won't be a problem but the solenoid may require more power then the Arduino can offer so an outside power source will be needed. Programming should be fairly straight forward.
Obtain the humidity sensor, and once you have that in hand and wired properly to the Arduino, learn to read its output (dump its values to the serial port for monitoring). When you have this done, set up your code to check the values, then turn an LED on and off in response to those values. When you have that working OK, hook up a simple transistor relay driver circuit in place of the LED. Use a relay with contact rated something like 125VAC @ 5A (that's probably overkill), and use that relays contacts to control the solenoid valve (you'll probably want to use a standard RainBird or Orbit sprinkler valve, since this is in a greenhouse - they run off of low-voltage AC, IIRC).
OK, here's where the newbie part comes in. Where can I find an example of a "simple transistor relay driver circuit"? Is this circuit and all other non-Arduino components on a breadboard? Finally, can you point me too a representative relay with the specs you suggested. Would I be better off to get some sort of Arduino kit and mess around with and then try to tackle this? Despite the high noob factor, I think I could catch on with enough patience from you folks with all the stars under your user names.
As far as the relay is concerned, there are tons of options; I usually order from All Electronics, but that may or may not be an option for you - but here is something close:
Hobby boards does a nice humidity sensor, but you will have to master communicating with 1-Wire devices to use it. More info on this and similar at....
Another, non 1-wire, possibility is a Sensiron SHT device. See....
I use the Sensririon SHT-11. It's a good sensor to use and the library already exists. I have one set up and use it with an LCD. I could provide some code to help if you choose to use Sensirion.
Thanks for all the pointers. Good one there cr0sh on the "let me Google this for you" link. I was in a hurry yesterday so opted out of my usual Google-fest. I think I have enough to get started so I'll start ordering parts.