Warming seeds in an outdoor garden


Spring is almost here and with that the green thumbs out there are preparing for their summer gardens. It’s usually a good idea to get a jump on all your gardening activities by starting seeds indoors, but with this comes the problem of making sure juvenile plants get enough sunlight. Putting a few seeds on a window sill will keep seeds warm enough to start germinating, but that will drastically reduce the amount of sunlight available for any given day. The best solution is to make sure the seeds are kept warm outside, but for wont of a properly placed clothes dryer vent [Tim] decided to make a solar soil heater using junk he had lying around.

[Tim] constructed a simple heater cartridge using a few 5 and 10 Ω resistors. These were sealed inside a piece of copper pipe with heat shrink tubing and silicone. The solution to powering this heater cartridge, though, is an impressive display of thinking outside the box.

The cartridge is powered by a solar lantern – the same kind you’d find illuminating a garden path at night and recharging during the day. After inserting the cartridge in a hill of seeds, the heater provides a little bit of warmth to get the seeds through the night. During the day, the battery in the solar lantern recharges, providing just enough power to cycle through another night.

It works for [Tim] in his native New England, so we’re betting it’s good enough for just about any growing region.

Watering system for your vegetable garden

The vegetables will be alive when [Dillon Nichols] returns from vacation thanks to this automatic watering controller that he built. This is the second iteration of the project, and deals mainly with replacing the electronics and UI of the controller itself. He detailed the hardware used for watering in a previous post. He plumbed in a solenoid valve with a hose threading on the output end for the soaker hoses snaking through the garden beds. This is a normally open valve but we’d suggest using a normally closed valve as a power outage will let the hose run continuously.

[Dillon] prototyped the design on an Arduino board, then moved to a standalone ATmega328 chip on some protoboard for the final design. He used a 3D printer to make the custom face plate which allows access to the three control buttons and provides a place for the character LCD to be mounted. In addition to the timer settings there is a manual watering switch as well. He used a typical mains light switch, wiring it with a pull-down resistor to make it work well with the Arduino. His explanation of the timer system can be seen after the break.

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Large-scale Arduino controlled greenhouse does some serious farming

[Instrument Tek] isn’t messing around with a hobby-sized greenhouse. In fact if it were any bigger we’d call it a commercial operation. But what interests us is the professional-quality greenhouse automation he built around and Arduino board.

The greenhouse is about what you’d expect to see at a nursery, except the footprint is somewhere around 10’x10′. It’s a stick-built frame with walls made of poly. Professional greenhouses monitor and regulate temperature and humidity and this one does just that. The video after the break starts off by showing the controller box. It has temperature, humidity, and light sensors that allow the Arduino to judge growing conditions. If it gets too hot, some slats are opened and a fan exhausts air from the structure. If it gets to cold, a series of light fixtures are energized. They contain heat lamps, as this setup is in northern Alberta, Canada and it can get quite cold some nights. The drip system is also automated, with a solenoid to turn water on and off.

In addition to that 3:26 show-and-tell, we’ve embedded a 27-minute video that shows how to build the controller box. So you can start you plants indoors on the rack, then populate the greenhouse when they get large enough.

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Scratch-build garden nursery uses Arduino monitoring

Starting your garden indoors helps to ensure large yields. This is because the plants get a head start before it’s warm enough for them to be put in the ground. But the process involves a fair amount of labor, ensuring that the lights are turned on and off at the right times each day, and that the temperature for germination and growth, as well as humidity, hit a certain target. It’s obvious that a bit of automation would be nice, and this Arduino-based garden nursery does just that. One of the things that sets this project apart is that it shows you how to go from an empty room to the bounty of plant starters seen here.

For the most part the equipment is what you’d expect, seed trays and covers, tray warming mats, and fluorescent light fixtures. the whole thing is given a small footprint thanks to an adjustable shelving unit. The Arduino is used in conjunction with a Sprout Board to add connectivity for switching the lights and warming mats. This is just a matter of driving a relay to switch mains voltage and can take any number of forms, including this home automation project we saw the other day.

[Thanks Tom]

Hacking color and battery life on a solar powered garden light

Give your garden lights a little bit more life by changing out the LEDs. In the process, you can also choose a different color if you like. It really is as simple as cracking it open and replacing the stock LED, but a bit of a change may also prolong the stored charge.

These garden lights consist of a small solar cell and an LED, both controlled by a small PCB powered from a NiMH rechargeable battery. Sure, you could try to put in a battery that has more potential, but if you replace the single LED with two of them in series, it drops the current consumption and increase the battery life. Just make sure to use super bright LEDs and the intensity change will not be all that noticeable. That comes partly from the fact that our eyes don’t detect intensity changes as well when a light is already very bright. And since it’s two LEDs, mixing colors is an option as we see above.

[Thanks Ken]

Garden sensors measure soil moisture and greenhouse temperature

[Andy] is getting his garden up and running. This year it’s been pretty cold so he decided to get small plastic domed tunnel which acts as a mini greenhouse. To help monitor that environment he built this sensor array which displays temperature and soil moisture readings.

Temperature is quite simple. He’s using a TMP36 sensor which is held a few inches above the soil. The moisture sensor is of his own design. It uses two building screws embedded in foam. These are pushed into the soil and a resistance reading indicates moisture level. By driving voltage on one screw, and measuring voltage on the other he gets some useful data. It’s not a standardized value, but observation over time will let him know how the scale relates to dry or wet soil.

During the build process he found that he needed a pull-down resistor on the probe used to take the moisture measurement. He also uses an I/O pin to drive the other screw. This gives him a way to shut off the juice when not taking a reading. We just hope he’s either got a current limiting resistor, or is using a transistor to drive it high.

Adding mobile control to your gardening

[The Cheap Vegetable Gardener] wanted to check in on his garden from the road so he wrote a control app for his WinPhone. The hardware work is already done; having been built and tested for quite some time.

The implementation comes in two parts, both shown in the chart above. The grow box is behind a firewall as you don’t want random folks turning on the water and grow lights on a whim. The first part of the interface takes care of this separation by providing a set of functions on the host machine. The second portion is the phone app itself which calls those functions and displays all the pertinent information from the status of the lights, heater, exhaust, and water pump, to the current temperature and humidity. He’s even used Google Charts to graph data over time. The app itself took about two hours to code with no prior experience, a testament to the level of approachability these tools are gaining.