Wireless Greenhouse Monitor: Update two

We have been hard at work developing our farmer-built Wireless Greenhouse Monitor that we were funded to prototype and test through a SARE farmer grant, which we outlined in our first post on this topic.

Louis, the lead hardware developer and programmer for our device, has been testing different configurations of parts, with an eye toward making things as simple and as useful as possible for farmers who want to monitor the temperature of their greenhouses from afar, using cell phone text messages.  

The heart of this tool will be an Arduino, an open-source microcontroller circuit board that is beloved by hobbyists and DIY-robot-builders.  Just as open-source computer programmers work on projects with the intention that their programs will free and accessible for all to use and modify, the Arduino is a design of a circuit board that is meant to be a platform free for all to use and to build using off-the-shelf parts.  The Arduino can handle simple tasks such as receiving signals from sensors, doing some calculations, and taking an action like turning on or off a switch or motor.  In our case, the Arduino will be sensing temperature in the greenhouse, processing that information based on the parameters that the farmer has set, and then sending (or not sending) the farmer a text message in response.  For example the farmer could set the Arduino to send out a text message alert whenever the temperature in the greenhouse rises above 90 degrees, or falls below 35 degrees.  Or the farmer could just set it to send out an update with the current temperature every hour;  or to simply reply with the temperature whenever the farmer sends a text message to inquire.  

Louis has been keeping track of developments on the project, and the current list of materials, on the page for the Wireless Greenhouse Monitor on the new Farm Hack Tools Wiki.  Check there for updates and to give your own feedback about the project:  how you might use it, features you hope it will have, etc.  This is a textbook Farm Hack opportunity for collaborative tool development!  

Meanwhile, we will be updating you here on the blog as we make progress on the tool.  Next step:  a trial run of assembly and testing in the greenhouse at Hearty Roots Farm, in two weeks. 

Tool Development Diary: Wireless greenhouse monitor

I have run my own farm for eight years, but because I have always farmed rented land, I have never lived within two miles of any of my greenhouses.  That means that I have had a lot of restless nights, wondering if my seedlings were alright.  Fortunately, a few collaborators and I recently received a grant that will help us to develop to new tool to solve this problem.  

Over the next few months, I will use the Farm Hack blog to document our progress as we brainstorm, prototype, test and tweak the tool that we have come up with.  

The baby seedlings at Hearty Roots Farm that we want to protect with our new monitor tool

The problem

CSA vegetable farmers like me have a lot at stake in our seedling greenhouses–  tens of thousands of plants, which we depend on for a productive season.  If it gets too hot, or too cold, a die-off in the greenhouse can have a devastating impact on the farm’s bottom line.  I can’t count the number of times that I have driven several miles from my home to my greenhouse just to check the temperature,  sometimes at 1am on a cold night, or at 1pm on a hot afternoon.  95 percent of the time, everything is fine:  the heater is fired up and keeping things warm;  or the fans on thermostats are working properly and venting out the heat.  A waste of a trip, except that without going to check on the seedlings, I probably wouldn’t have been able to fall back asleep.  

There are alarms that farmers can buy and install in their greenhouses to monitor temperature.  Some of them just sound a siren if things get too hot or cold.  Others hook into a land line, or an internet connection, to call a farmer with a temperature alert.  None of those were going to work for me, since  my greenhouses aren’t near a land line or an internet connection,  and they are miles away from earshot.  This situation is common to a lot of young farmers who are growing on leased land.  

Super-sad photo of some lettuce seedlings that fried when our greenhouse got too hot

An idea for a solution

At Farm Hack New Hampshire last fall, we had a working group on “smart farm” tools.  We were lucky to have both farmers in the group, as well as some allies with skills in open source software and hardware development.  I joined the group to discuss how farmers might use sensors, open-source circuit boards, and computer code to create DIY tools that could make our farms more efficient and more sustainable.  We threw around lots of ideas, some crazier than others.  One project that seemed straightforward and useful was creating a farm-built greenhouse monitor that could deal with any problems that might come up.  We knew that the possibilities for this were wide open:  it could monitor soil moisture and turn on sprinklers, or temperature and send turn on fans, all while collecting data that could allow the user to monitor the temperature trends in the greenhouse over the day.  

We wanted to make the first attempt at this tool simple and useful, so we decided to tackle the problem outlined above.  We wanted a greenhouse monitor, built from easily accessible parts by a farmer without major electronics skills, that would send a SMS text message to a farmer if there was an “alert” situation in the greenhouse, or that would just send regular status messages about the state of the greenhouse.  We decided we’d also like to make the communication two-way, so that the farmer could text the greenhouse and get a response with the current temperature.  We knew that many farmers didn’t have a landline or internet access at their greenhouses, so we wanted our tool to operate using cellular networks to communicate.  And it would have to be cheap enough to appeal to cheapskate farmers!

Applying for a grant

A subset of our team set out to apply for a grant to fund the development of this tool so we could build it, document it, and share it with the farmer community at large.  RJ and Louis (open-source computer programmers and hardware developers) joined up with me (Ben, vegetable farmer) to apply for a USDA Sustainable Agriculture Research and Education (“SARE”) Farmer grant, which funds farmers to carry out research and share it with other farmers.  

We just learned this week that we got the grant!  So we are excited to spend a chunk of time this spring putting together a prototype of this tool, getting some other farmers to test it, and documenting the whole process to share with the world.  This is the first step, and you can keep tabs on the project as we go forward right here at Farm Hack.


Katchkie Farm’s greenhouses

One of Katchkie Farm's greenhouses. Photo from Blondie and Brownie blog.

Recently I visited Bob Walker at Katchkie Farm in Kinderhook, NY. He gave me a tour that included lots of inspiring innovations, probably the most elaborate of which is his greenhouse setup.

The hot water furnace that burns waste veggie oil, located in the farm's shop across from the greenhouses.

Last year Bob installed a new heating system for his three greenhouses: in one, to heat the soil directly for in-ground crops; and in the others, to heat the benchtops where trays of seedlings sit. There are lots of efficiencies in the system, which in ideal circumstances heats some of the greenhouses year-round and uses waste vegetable oil as a practically free fuel source.

The manifold fed by the furnace. The blue fixtures are pumps that feed water into the four loops when the thermostats tell them to. One loop for each of the three greenhouses, plus one to heat the shop's radiant floor.

The heart of the system is the waste oil furnace located in the farm’s equipment workshop, just across the driveway from the greenhouses. The furnace is tuned to burn waste veggie oil with optimal efficiency, heating water to ~180 degrees F. The water can then be sent through a manifold to heat any of the three greenhouses, or to heat the workshop through a radient system of tubing in the concrete slab. From the furnace, the water flows through separate lines of pex tubing through an insulated pipe underground, one out to each of the greenhouses.

The control panel. Thermostats in the greenhouses can call for more super-hot water to be fed into the loop.

Each of the greenhouses has an independent loop of hot water lines that is constantly circulating water, thanks to an electric pump in each house. The loops each have a thermostat that, when triggered, will call to the controller in the workshop to cycle on the pumps at the main manifold, by the furnace, to pump more hot water into the loop, until it is brought back up to the desired temperature. This system of injecting very hot water into the loop only when needed eliminates the need for the heating water to be constantly flowing back to the furnace as it circulates.

The manifold for the loop of pex tubing in the ground of the production greenhouse. The electric pump in the photo constantly circulates the water through the loop, more hot water form the furnace is sent only when needed.

In the production houses, the ground is heated by pex lines that run under the soil surface; Bob installed the pex by jury-rigging a way to pull the lines through the ground, attached to a chisel plow point; no excavation needed.

The seedling greenhouse. Small rubber tubes run under the surface of each table, to heat the seedlings from below.

In the seedling houses, the heating water runs through main lines and then out into small rubber tubing that snakes across the bench tops, sandwiched between the seedling flats and a layer of insulation below. There are manifolds and valves allowing individual sets of tables to be heated, or excluded from the loop.

The rectangle at the bottom is a heat exchanger, to transfer the heat from the furnace water to the water in the greenhouse loop. The white box is an on-demand hot water heater, no longer used, although it could be called into service as a backup heater.

Before Bob installed the main furnace for all three greenhouses, the water for this loop was heated with an on-demand hot water heater in the greenhouse. It was retrofitted once the new furnace was installed, but because the small rubber tubing lines heating the benchtops can allow oxygen into the heating water– which could make for a rusty furnace– there is a heat exchanger so that the water in the greenhouse loop never actually mixes with the water from the furnace. In the seedling houses there is also a forced air heater that cycles on if the air temperature falls below freezing, which is rare. My visit was during mid-March, when nighttime lows were still in the mid-teens, but there were nearly ready-to-plant tomato seedlings, soon to be moved into the in-ground greenhouse.

The bench tops roll on the round pipes, allowing the aisle between tables to be moved, and conserving greenhouse space.

Another great feature of the seedling house is the design of the seedling benches. The frames are farm-built of galvanized square tubing, and the table tops rest on top of round lengths of galvanized pipe. This allows the tables to roll back and forth on the frames, which means that tables can be parted to create an aisle for access, and then pushed back together to close the space, allowing an aisle at the next table down the line. This means that there only needs to be room for one aisle in the entire block of tables, conserving as much greenhouse space as possible for seedlings.

Detail of the manifolds feeding the greenhouse bench top heating tubes.


The in-ground heated greenhouse. Pex tubing runs under the soil.


The schematic for the heating system.

Soil Flat Dibbler

This project comes from:

Seth Roberts from Weathervane Farm in Buena Vista, CO

Here is the link to his farm’s lovely website:


Soil Flat Dibbler


Who the project is for:

Vegetable and/or Flower Growers, Nursery Growers

Range of how much it might cost to build:

about $10

What skills are necessary to complete it:

Pretty intuitive, might need a very basic knowledge of using a drill.

Summary of the project:

The project cuts down time for planting flats of seeds.  The Soil Flat Dibbler can make multiple indentations for dropping the seeds into the flats at a consistent depth.