This
instructable is a guide for setting up an automated gardening system
using an arduino and other cheap electronic parts. It allows
sustainable gardening by using sensors to determine soil moisture, as
well as a webscraper to determine future weather. It uses this
information to save water by only using the requisite
amount. Requirements for this project include experience soldering,
some basic programming experience, and much patience for debugging.
See video for example of why we need this.
See video for example of why we need this.
Step 1: Build-Moisture Sensors
The
moisture sensors rely on the resistivity of water to determine
the moisture level of the soil. The sensors measure the resistance
between two separate nails by sending a current through one of them and
reading a corresponding voltage drop due to a known resistor value. The
more water the lower the resistance, and using this we can determine
threshold values for moisture content.
We will use three such sensors and use a multiplexor to alternate reading between them without using more than one arduino analog port.
While we will include a circuit board diagram, we recommend building the circuits on a breadboard first which will allow for both understanding and debugging.
Each sensor uses two nails, a 100 ohm resistor, and a 100 K-ohm resistor. We built a casing for each sensor with acrylic tubes, however this is not necessary.
We will use three such sensors and use a multiplexor to alternate reading between them without using more than one arduino analog port.
While we will include a circuit board diagram, we recommend building the circuits on a breadboard first which will allow for both understanding and debugging.
Each sensor uses two nails, a 100 ohm resistor, and a 100 K-ohm resistor. We built a casing for each sensor with acrylic tubes, however this is not necessary.
Step 2: Build-Moisture Sensor- 1
The
first step is to find two equal length nails of any type, although we
found that longer and non-galvanized nails worked best (galvanized nails
do not work at all). Next, a wire needs to be soldered to each nail.
It is best to use weaved wire since it is flexible and less likely to
break during use. The nails act as a heat sink, and to counteract this
they must be heated before soldering. A hotplate was used to get the
nails very hot.
A word of caution, as the name implies the hot plate gets extremely hot, as will the nails, so please use pliers to remove the nails from the hotplate.
It is useful to shrink wrap the soldered parts of the nails, especially if you are not planning to make a probe structure.
A word of caution, as the name implies the hot plate gets extremely hot, as will the nails, so please use pliers to remove the nails from the hotplate.
It is useful to shrink wrap the soldered parts of the nails, especially if you are not planning to make a probe structure.
Step 3: Build-Moisture Sensor-2
The
next step is to wire the nails to the arduino. Use the circuit diagram
provided. The sensor works by sending a fake AC current by alternating
DC current between the two nails. The analog voltage is then read
and a moisture level can be inferred. Our code for the whole project
will be available. A picture of the finished sensor with acrylic
covering is on the next page.
We read an input voltage into a multiplexor from a voltage dividor created by the 100K resistor. The 100 Ohm resistor, attached to the other lead of the sensor, is used for current limiting. Current limiting imposes an upper limit on the current coming into the arduino, which protects it from short-circuiting.
We read an input voltage into a multiplexor from a voltage dividor created by the 100K resistor. The 100 Ohm resistor, attached to the other lead of the sensor, is used for current limiting. Current limiting imposes an upper limit on the current coming into the arduino, which protects it from short-circuiting.
Step 4: Build-Moisture Sensor-3 (optional)
Take
a hollow acrylic tube and attach it to a pointed front with two holes
for nails. Seal the bottom from water with silicone glue. Make sure that
the nails are not touching as this will short the circuit. Use a
rubber stopper to seal the top. It is important that the nails be equal
distances apart on each of the moisture sensors, as any variation could
affect resistivity readings from one or more of the probes.
Step 5: Build-Moisture Sensor-4
To
improve performance we used three soil moisture sensors. However,
there may not be enough analog pins on the arduino to accommodate all of
these depending on what other attachments you are using. We solved
this problem by using a multiplexer, which allowed us to switch between
and read from each of the three pairs of sensors. The circuit diagram is
given below.
Step 6: Build-Temperature Sensor -1
For
the temperature sensor we used a TC-74 chip. The wiring here is pretty
simple and is shown below. It is recommended that you use 1K resistors
on the ports connecting to the arduino (SDA, SCLK). The sensor works
by exposure of the chip's metal tab. Attaching this metal tab to a piece
of sheet metal will increase the sensor's sensitivity over a wider area
and improve performance.
Temperature readings are used to normalize soil moisture content readings, since higher temperatures will increase resistivity between the nails, potentially giving inaccurate readings. It is important to correct for temperature so the arduino will trigger watering at the appropriate time.
Temperature readings are used to normalize soil moisture content readings, since higher temperatures will increase resistivity between the nails, potentially giving inaccurate readings. It is important to correct for temperature so the arduino will trigger watering at the appropriate time.
Step 7: Build-Circuit Board
Make
a circuit board. The schematic is shown below and the board file is
attached. We used the program EAGLE to design the board, and the files
are in that format.
garduino.sch72 KBgarduino.brd17 KBStep 8: Build-Pump System-Relay
The
pump system we created uses a small fountain pump attached to the
arduino with a solid state relay, allowing the arduino to turn the pump
on or off automatically. Strip off a segment of the pump's insulating
tubing, and cut only one of the inner wires in half. Attach each end of
the newly cut wire to the relay's two outputs. Be careful to avoid
touching any exposed metal on the relay, as it is at a high voltage. We
recommend putting electrical tape over the exposed wires. Finally,
connect the relay's ground to the the arduino's ground and the relay's
input to an arduino digital pin (in our case 5).
Step 9: Build-Pump System-Reservoir
The
submerged pump needs a constant amount water to function properly. To
automate this process we used a float valve that attaches to a hose and
opens when water is needed and closes when the water level rises. Make
sure to drill the hole high enough to give the float valve room, and
that the tank is wide enough to accommodate the float.
Step 10: Build-Pump System-Tubing
Drill
small holes through a length of plastic tubing that is the correct size
for the pump. Then cut pvc pipe into 5-8 inch segments, punch small
holes through their centers, and thread the plastic tubing through the
holes. These will be staked in the earth and provide a stable base for
the tubing. One may want to put a point on the bottom of the small pvc
pipes so they are easier to stake. There are many other ways to build
the sprinkler system, so check out your local hardware store for some
inspiration.
Step 11: Connect
When
connected, the circuit should look like this. Note: this picture
includes a wifly shield that will hopefully be implemented in the
future. Notice that we connected the relay to the wifly shield. It
would be better to put this on the board, however, this was an oversight
on our part.
Step 12: Build-Plastic Enclosure (optional)
We
then used a regular plastic box 15x10x6 cm to enclose the circuit board
and a separate box to enclose the relay. The arduino and relay need to
be protected from the elements if they are to be placed outside in a
garden. This separation allows the relay to get very hot but not damage
the circuit board, however, it should not get very hot if using the code
provided at the end.
Step 13: Code
The
garduino uses arduino and python programs that interact with one
another through the library pySerial. The arduino checks the soil
moisture content and if low, triggers the python web scraper and find
tomorrow's weather forecast. If the forecast includes rain, python
tells the arduino to delay checking soil moisture content for the next
24 hours. If the forcast is dry then the arduino will be triggered to
water. After this, the system will recheck soil moisture content every
twenty minutes to see if more water is needed. if water is not needed
at the initial watering check, or after a recheck, the system waits for
24 hours and the process is repeated.
For the scraper to work, you need to download and install:
- BeautifulSoup
- urllib2
- pySerial
I would recommended creating a github account (https://github.com/) and pulling everything from github.
We used yahoo's weather api to find tomorrow's forecast: http://developer.yahoo.com/weather/
Look here for some good documentation:
- http://www.crummy.com/software/BeautifulSoup/ (Beautiful Soup documentation)
- http://www.regular-expressions.info/ (Regular Expressions, useful for parsing html)
- http://www.linuxforu.com/2012/03/building-image-processing-embedded-systems-using-python-part-3/ (best example of pySerial I found...much better than pySerial's documentation)
- http://www.akeric.com/blog/?p=1140 (another good example of pySerial)
Thanks to Joseph Long for help with the code.
For the scraper to work, you need to download and install:
- BeautifulSoup
- urllib2
- pySerial
I would recommended creating a github account (https://github.com/) and pulling everything from github.
We used yahoo's weather api to find tomorrow's forecast: http://developer.yahoo.com/weather/
Look here for some good documentation:
- http://www.crummy.com/software/BeautifulSoup/ (Beautiful Soup documentation)
- http://www.regular-expressions.info/ (Regular Expressions, useful for parsing html)
- http://www.linuxforu.com/2012/03/building-image-processing-embedded-systems-using-python-part-3/ (best example of pySerial I found...much better than pySerial's documentation)
- http://www.akeric.com/blog/?p=1140 (another good example of pySerial)
Thanks to Joseph Long for help with the code.
Een wormenbak is een ideale methode om keukenafval te recyclen tot een rijke donkere, naar bosgrond ruikende grond of bodemverbeteraar. Het grote voordeel van wormencompost is dat men hem zowel binnen- als buitenshuis kan maken. Zo kunnen ook mensen die op een appartement wonen hun groente- en fruitafval composteren.