Linux sprinkler controller project
Doran L. Barton
fozz at iodynamics.com
Mon May 11 00:17:57 MDT 2009
On Saturday 09 May 2009 22:06:09 Dave Smith wrote:
> If anyone has any ideas, I'm all ears.
I've never actually done this, but, like you, I think it's stupid to buy these
cheesy controllers for $30 that do nothing more sophisticated than cron jobs.
As far as how sprinkler systems work, it's really simple. The valve opens when
you apply a voltage to it. Most controllers have around a 15V DC output. The
valves are pretty dumb and will probably open given 12V - 30V.
Now, most microcontrollers like the Arduino have digital outputs, meaning they
can output a voltage (usually 5V) or not (0V). Think 1 and 0.
Now, the simplest thing to do is connect the digital output to one side of a
relay. A relay is a mechanical switch that turns power to one circuit on and
off based on the state of another voltage, the control voltage. Relays are
used to switch a higher-voltage circuit from a low-voltage signal, which is
exactly what you want to do.
Here's an example (turn on your fixed-width fonts for best results):
Your Linux PC---(usb)--->Arduino--(pins 13 and 14 (ground))---+
15V DC power supply------>Relay<-----------------------------+
Then, you write a simple program using the Arduino API to set the state of
pin-13 to high (applied voltage). This engages the switch inside the relay,
letting 15V out to the sprinkler valve. Just make sure none of the electronics
are in the path of your sprinklers.
< http://www.makershed.com/ > has some nice Arduino hardware and clones as
well as good howto videos and other helpful information.
Doran L. "Fozz" Barton <fozz at iodynamics.com>
Open-source developer, sysadmin, consultant, and all-around geeky dude
"Push this button in case anything happens."
-- Seen above elevator emergency call button
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