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I am studying greenhouse design and operation. Part of the task involves automation. Commercially available drip irrigation systems and timers seem adequate to the task, but I am currently looking for ways to automate the opening and closing of vents and the cycling of fans. I could get contact closures from the irrigation system outputs but need the actuators, or the parts to build them. Left to my own devices they might literally be my own devices. I would have fun designing and building them but it could seriously delay the projects.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Mar 4th, 2012 at 03:56:48 PM EST
A related area is the integration of temperature sensors into the above described systems. I certainly do not want to try to develop my own software. I want something easily programmable, no 'school' required. Any thing pop into anyone's mind?

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Mar 4th, 2012 at 03:59:08 PM EST
[ Parent ]
It doesn't exactly pop but of course all these systems are available to professionals, just too expensive and out of scale for small amateur greenhouses. But maybe you're planning something Really Big...
by afew (afew(a in a circle)eurotrib_dot_com) on Mon Mar 5th, 2012 at 01:40:58 AM EST
[ Parent ]
Yes! I have been looking at some of the more professional systems. They look like $1,500 and up to do what I need. I am looking for some way to open and close vents at the base and ridge at predetermined intervals. I think I should be able to do that cheaper than what is commercially available. Oh, for easy access to some of the military surplus stores in LA just now. A timer, a reversible motor and some limit switches could get me started. A garage door opener is a whole lot cheaper than what they are asking.... Perhaps some stepper motors.

I have decided to start small with a hot box/germinator made of plywood and 2x2s on the bottom and back and corrugated translucent panels used for patio covers for the sloping front. If I make the back about four foot high it will work for all seedlings and can serve as a kitchen garden for lettuce, cilantro, green onions and herbs. I plan on using salvaged 2 liter soda bottles along the back wall to provide thermal mass to dampen temperature swings,  have a bunch saved up and get another about every other day. (Someone in the household has a soda habit.)

I have a south facing shop wall along which I can place it and have dropped off an irrigation stub and control wire at that location. A small, programmable drip irrigation system is well under $100 and I can get power from the shop panel. I just don't want to have to open and close the vents by hand every morning and night, depending on temperature and wind. Seems like that shouldn't cost ten times the cost of the rest of the hot box. Perhaps I can use motorized dampers from the HVAC industry, or just a fractional HP gear motor, a shaft and some pulleys. Definitely open to suggestions.

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Mon Mar 5th, 2012 at 02:21:08 AM EST
[ Parent ]
Hi ARG, I've tried all the irigation methods out there.  The best results by far for me (australian climate - water supply restricted, very hot summers) have come from flood and drain.  I use a very simple control system made from an ornamental pond pump and a digital timer.  The pump turns on and fills the grow beds to the level of an overflow.  Then after 30 minutes or whatever the pump turns off and the water drains back out through the pump.  Very cheap and very robust.

If you keep fish in your supply tank you get free symbiotic water cleaning and plant fertilization too.

With sufficient water you can even out day-night temperature swings to avoid heating and cooling.  You can heat the water rather than the air in the greenhouse and thus reduce losses from the glazing (because you keep the roots warm but let the leaves cool down).  watering the roots rather than top watering of course reduces fungal problems.

Then I have a simple wax piston type vent opener for super hot days.

This system has been running almost maintenance free for 5 years (the inlet occasionally gets roots in it).

Spending more on glazing insulation (adding an extra layer of plastic film on the inside, or using triple rather than double wall PC) is typically better value than spending more on the control system.

by njh on Thu Mar 8th, 2012 at 09:31:37 AM EST
[ Parent ]
I have no experiences of green-houses but I have heard that fungus is a big problem. Is that always the case or is there somethng simpla that can be done about it?

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by A swedish kind of death on Thu Mar 8th, 2012 at 01:44:19 PM EST
[ Parent ]
I use lots of fresh air when I can, and sunlight helps (UV), and air movement in general (people often add fans).  There are fungucides, but they are rather close to humanicides.
by njh on Fri Mar 9th, 2012 at 12:54:22 AM EST
[ Parent ]
The best thing with greenhouses is not that you can grow things in them, but that you can stay out eating and drinking for several extra months per year!

Peak oil is not an energy crisis. It is a liquid fuel crisis.
by Starvid on Fri Mar 9th, 2012 at 10:39:51 AM EST
[ Parent ]
Any information you can send me on the wax piston vent opener would be appreciated. My address at my signature line works. I would e-mail you, but... A lot of the info I have read has been developed in Australia.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Mar 11th, 2012 at 07:44:16 PM EST
[ Parent ]
I found some products that seem to be what you described. They use a temperature sensitive paraffin foam to actuate an arm that can be adjusted for the desired temperature. Thanks for the tip.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Mar 11th, 2012 at 07:56:23 PM EST
[ Parent ]
by njh on Sun Mar 11th, 2012 at 09:47:08 PM EST
[ Parent ]
Thank you. I 'knew' something like that existed and it is available from a supplier in a neighboring state.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Mon Mar 12th, 2012 at 12:54:35 AM EST
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