This year (2004) I have started having a little play at making a monitoring system within the greenhouse, I was originally planning on using X10 equipment to automate the greenhouse. Due to the expensive nature of this equipment in the UK though I have decided to use a different method to monitor and automate the greenhouse.
I then decided to purchase a development kit to use for this purpose.
This equipment allows you to connect sensors and switches etc. to a computer for reading and also to turn things on and off, This is all done with two wires which means the only thing I needed to connect from my house computer to the greenhouse was a small cable with two cores.
This system appears to be used quite extensively by home users who have weather stations set up, which makes it ideal for my kind of measuring and monitoring setup.
This computer I had was a VIA EPIA 5000 Fanless Motherboard in a tiny case, This combination only uses approximately 10 watts of electricity, Compared with 250 watts like a normal PC.
It’s also completely silent as there it’s passively cooled and there are no fans used in the computer.
The computer is connected to all the 1 wire products by a simple adaptor plugged into the serial port, This adaptor came with the development kit I purchased.
I decided that to start with I needed to be able monitor the temperature within the greenhouse (And later outside the greenhouse), Check for nutrient levels being low in the tank and also to be able to switch off and on both a heater and a fan, The products below are are the ones I chose for this purpose, All are low cost items.
1 Wire items used in the Greenhouse
DS 1820 – 1 Wire Thermometer
DS 2401 – Silicon Serial Number (Switch)
DS2405 – Addressable Switch (Fan)
To connect the low nutrient level sensor (Home made off course as you can see in the picture here.) was simply a matter of connecting the serial number chip DS2401 to the same two cores but through a microswitch. The microswitch is connected via a piece of string to a floating piece of lego which pulls the microswitch on when it starts floating to low.
The trickiest thing to get working was always going to be the switching of the fan and heater, As I don’t like working directly with electricity I decided the easiest and safest method for me to use was going to be to modify a battery powered remote control I already had which transmits commands to remote control plug sockets.
This meant that I did not have to touch any electricity just connect some relays from the 2 DS2405 addressable switches I had to the remote control. You can see the finished product in the photo. The large plug circled is the one attached to the cooling fan and the remote control circled is the one attached to the relays.
This looked like the ideal piece of software for the job. Unfortunately it was not able to talk directly to the 1 Wire items I had connected so I would have to write a small piece of software which would pass information between the 1 wire items and the housebot software.
Fortunately I’m a computer programmer by trade, It also helped that the example programs supplied with the dallas 1 wire development kit were in the same computer language that I am familiar with (Delphi).
After I had all this software in place and connected to the 1 wire items using the serial port adaptor supplied in the development kit it was a simply matter of configuring some scripts within the Housebot software. To start with I configured scripts which simply monitored the nutrient level, You can see that script here.
As you can see in the script the housebot software also allows you to output speech, This allows me to do cool things such as make the computer say ‘Nutrient Level is running low’.
The system also looks after cooling and circulating air around the greenhouse with the fan. It also adjusts the time this is run by monitoring the temperature. When colder days set in later in the year I will be trying to use a heater in the greenhouse to try and extend the growing season.
Finally I have written another piece of software to run alongside the Housebot software which regularly updates a page on the internet with the current status of the greenhouse including a graph plot of the ideal and actual temperature.
As this is going to be an ongoing thing this is just a brief description of the system I’ve currently got, As time progresses I’ll be expanding my system and also this page to match.