pi_plant

Overview

(Long) weekend project to monitor and water my plant with a Raspberry Pi. The app was developed for Raspbian Wheezy with an arduino two-prong soil moisture sensor via a MCP3002 analog-to-digital converter, and an arduino relay board to control a 110 VAC water pump.

It makes a couple of assumptions:

Moisture Sensor:

• Now includes a Kicad PCB design for interfacing with a MCP3002 10-bit SPI Analog-to-Digital Converter. The Pi talks to the ADC via its SPI interface. Includes all the manufacturing files required to fab the board (which I had OSH Park make for me for $7.85 shipped, which required about $15 in components from Digi-key.)

  

• Includes three 2N3904 transistors to allow the Pi to control the power provided to the MCP3002 & the two analog sensors:

  

(Leaving these two-prong type of sensors powered on 24/7 can lead to galvanic corrosion, so it's probably better to turn them on when needed.)

• Provides two analog measurement channels. Also supplies VCC & GND (in case the moisture sensor requires it) for each.

Water Pump:

• Assumes there is a power pin to activate the pump. My Pi's 3.3V GPIO was able to activate/deactivate my relay board directly, but if you're having issues you could always use a NPN-transistor network as shown above.

Dependencies

pi_plant was developed on Ruby v2.1 and Rails v4.0. Several gems were utilized to make development easier:

gem 'bootstrap-sass', github: 'thomas-mcdonald/bootstrap-sass'
gem 'figaro'
gem 'draper'
gem 'lazy_high_charts'

Installation

1. Clone the repository.

2. Create a /config/application.yml file with environmental variables holding all your secret keys (see figaro's documentation for more details) and add it to your .gitignore file.

   RAILS_SECRET_KEY_BASE: '<rails secret key>'

3. Schedule the sample rake task to take periodic soil measurements.

   crontab -e
   00 00, 12, * * * * rvmsudo rake RAILS_ENV=production sample

   Note: the Pi requires root access to interact with hardware

4. Start the webserver

5. Create a plant with the GPIO pins used in your circuit.

Bill of Materials

Find No.	Qty	Part Number	Description	Approx. Extended Cost
1	1	756-8308	Raspberry Pi v2	$40
2	1	SDC10/8GBET	Kingston 8GB microSD Card	$8
3	1	EW-7811Un	Edimax 802.11n USB Adapter	$10
4	1	B00E0NTPP4	SunFounder 2 Channel 5V Relay Shield for Arduino	$7
5	1	B00AYCNEKW	sunkee Soil Moisture Sensor	$3
6	1	B001BOD9JI	TOM 3.5gph Aquarium Pump	$16
7	1	kTJJCOss	OSH Park Custom PCB	$8
8	1	MCP3002-I/P	MCP3002 2-Channel 10-bit ADC	$2
9	3	2N3904BU	40V NPN Transistor	$1
10	3	CF14JT1K00	1kOhm 1/4W Carbon Through Hole Resistor	$1
11	2	0022288363	Molex 36pos Right-Angle Pin Header	$4

TODO

• Custom PCB for interfacing with the MCP3002 (experimenting with Kicad)

Keywords

• Raspberry Pi
• RPi
• Ruby on Rails
• Kicad
• MCP3002
• Home Automation

Credits

pi_plant is the product of Ryan Ringler. It was developed as a (long) weekend project to experiment with the Raspberry Pi, Rails, and Kicad.

License

pi_plant is licensed under the MIT License. Please see the LICENSE file for additional details.