Archive for June, 2012

Don’t kill the plants!

Sunday, June 24th, 2012

Hi again. It’s me. I’m back. I’ve had a few sysadmin-y posts recently with the new job and all, and I’m starting to get back in to home improvement projects as well. No, I haven’t finished the basement – I’ve made some progress but not much, although I keep at it. I’m just naturally lazy and it’s taking a while to get over that and get back to work.

I am however a bit of a tinkerer. I started playing with an Arduino (no this isn’t a computer geek post), and I wondered if it could be adapted for some “maintenance” type tasks around the house – like watering plants. Turns out, it can! I haven’t put together the Arduino brains yet, but that will be soon – I started out by putting my 35 gallon trash can on the back deck and using it as a rain barrel.And not just a rain barrel – I redirected the air conditioning condensate tube to put the condensate into the barrel instead of just letting it drip out onto the lawn in one spot. I’m not much interested in spending $100 on a rain barrel when I can use a $30 lawn trash can for the same purpose. Then I got a drip irrigation system commonly used to convert Rain-Bird type pop-up sprinklers to drip systems, and added a 130 GPH pond pump to the mix. So far I’ve spent about $50 and I have enough materials to irrigate up to 6 different “circuits” of flower beds and pots from the rain barrel. Right now, it’s a dumb system – the pump will keep going until the water level in the rain barrel is too low, possibly drowning the plants I want to water, even with only a 1GPH drip.

What’s next? Well, I’m starting with some 1/2 inch tubing (1/2″ ID), cutting it about 1″ long to make some plaster-of-paris plugs. I put two galvanized nails in each plug, then let the plater fully cure around the nails, cutting off the tubing when it’s cured. This gives me a “sensor” that I can use to measure the water content of the soil, by measuring the resistance across the plaster with the Arduino. The wetter the soil is around the plug, the more water will be in the plug, thus the less resistance there will be.

Then there’s the other half of the “brains”. I have a test solenoid valve on order that I will be putting in-line with each irrigation circuit. The Arduino will use the data supplied by the plaster plugs to either open or close the valve, effectively starting to water the plants as soon as the soil gets too dry, and stopping once the soil is no longer too dry. Each valve is $16, the Arduino runs about $60, and the various bits like a MOSFET, resistor, diode and things will run around $15 per circuit. So the entire 6 circuit system will cost a grand total of $60+$15*6+$16*6 + $50= $60 + $90 + $96 + $50 = $296. Seems a bit pricey, but then consider that using the rain barrel and pump, and redirecting the A/C condensate to the rain barrel, will save and average of (based on other people who have done the condensate thing without the Arduino intelligence) $600 / year in water costs, plus the intangible benefit of having perfectly-watered plants year-round, even in the extreme summer heat, without having to actually water then yourself… I’m liking this idea!

Plus, it appeals to the geek in me.