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[on:]

I am trying to create an automatic mist system for my chameleon so he can be misted frequently while i am gone. I have been searching for a timer and a valve to run the system off of but all i could find so far is a sprinkler timer and valve. Unfortunately, the timer will mist him during the night and the misting times are all one minute or longer when i need a misting time of ~30-45seconds max with the nozzles that i have. I have come to the conclusion that the only way i am going to have an automatic system that won't mist at night or for too long is to get an arduino and program it to open open and close a valve. I can get just a normal solenoid sprinkler valve to work but it runs on 24 volts.

How would i hook up and program an arduino to a solenoid valve (i.e. sprinkler valve)  so it will open for 30-45 seconds and then close again multiple times during the day for a set number of hours, say 8 am to 7 pm?

[Reply #1 on:]

Driving the solenoid can be done several ways.

http://www.arduino.cc/playground/Learning/SolenoidTutorial
In this case a 12 volt power supply was used to switch the solenoid, but it could be transformed to operate on 24 volt. The circuit has an optocoupler to protect the arduino, which isn't really needed by the way.

A relay could also be used.
http://arduino.cc/playground/uploads/Main/relays.pdf

Next, you'll have to keep track of time.

The arduino doesn't have an RTC on board, so you'll have to add one for a few bucks.

You might... also use a light sensor to determine whether it's day or night, but that may cause little mist in winter and perhaps too much in summers.

It is possible to turn on the mister for a determined time several times a day, but you'll have to write the program for it.

Since you're more or less "playing God" and have an living animal depending on your skills, it's best to be sure it works perfectly. I don't know much about chameleons, but know of a few DIY-projects with fish that decided to swim belly up after automating fish-tanks while having a few programming errors.

If you would like to you could also integrate other stuff like a humidity-sensor, temperature sensor.
That way you might be able to check how humid the air already is and adjust the misting automatically.

A lot is possible I guess.

[Reply #2 on:]

thanks for the help! Im not too worried about the possibility of him "going belly up" like the fish tanks because the misting is only to control humidity and supplement his drinking because they will lap water off leaves. He has a fountain to drink from constantly that is always on so he always has a source of water.

[Reply #3 on:]

Someone really should be collecting some of these great but unusual Arduino project ideas.

'A chameleon mister' - every home should have one

Could you adapt one of those PIR activated smell squirting things have started to infest our homes (an Airwick Freshmatic I believe)? I got one to play with after a suggestion from duncaninspain. It has a PIR sensor and timer to prevent over-deoderising. It uses a pressurised canister, and a little geared motor that depresses the nozzle momentarily.

From what you have said, it sounds like its not on the right scale for what you need.

[Reply #4 on:]

Someone really should be collecting some of these great but unusual Arduino project ideas.

'A chameleon mister' - every home should have one

Could you adapt one of those PIR activated smell squirting things have started to infest our homes (an Airwick Freshmatic I believe)?

Chameleons are... cold blooded, I guess they have no problem fooling a PIR sensor.

I do agree this one should be included should our kids build an Arduino-museum one day.