2 - Required Components

OK lets get started with a description of all the equipment needed to complete this project;

Raspberry Pi - Model B - 512MB

Whilst this project will work with a Model A Raspberry Pi I have opted for a Model B unit given that it has the facility of being able to plug directly into my LAN via the Pi's onboard RJ45 port. As you will see in my later Blogs, having the Raspberry Pi sitting on its own IP address will be a requirement for testing purposes and SSH access. That said, you could always use a WiFi dongle plugged into the Model A's USB port - but personally I prefer to have the Pi connected directly into my LAN.

You will also need an SD Card to boot the Raspberry Pi. My current setup for this project includes a 16GB Class 10 SD Card (mainly because it was laying around at the time) but a cheaper 4GB SD Card will suffice.

When purchasing your SD Card it is worth bearing mind that not all SD Cards function well with the Raspberry Pi. To be sure that you have a card that will function without problems please refer to the Raspberry Pi -  SD Card Compatibility Chart. Last but not least you are going to need a power supply to power the Raspberry Pi. For the purposes of this project make sure that you purchase a power supply that has a 5VDC / 1.0A output (minimum) complete with a micro usb connector to plug into the Raspberry Pi.

PiFace Digital

The PiFace sits nicely on to top of your Raspberry Pi, connecting via the Pi's GPIO socket, and is where all of your inputs and outputs will be connected. Python scripts detailed futher on in this project will tell the PiFace what to switch .... when to switch ... and under what conditions.

• Make sure you get yourself a case that encapsulates both the Raspberry Pi and the PiFace. Later on in the project we will be installing both of these in an enclosure ... strapped to a (metal) DIN rail. To avoid damaging the circuit boards they will need some form of protection.
  

Float Switches

Within this project we will be detecting the high level and low level float status in two water tanks, you will therefore need to have four float switches to hand. You can of course modifiy this project to suit your own requirements but as a minimum two float switches will be required.

When setting up and testing this project you will find it much easier to simulate the float switches being activated by using a 4 gang light switch. You will need the float switches at the end of the project - but for a minimal cost the light switch makes life a lot easier along the way.

24v Water Pump

The size of the water pump will be determined by size of your garden irrigation system. If like myself you already have an irrigation system served by mains water and pressure reducing valves you will know what works for you. If you dont know what mains water pressure you currently have, pressure meters are widely available that can clip onto a water tap. Once you know your mains pressure you can size your pump accordingly.

I have opted for a 24v water pump on this project as I have tried to ensure that. whereever possible, the majority of components being used in this project are working on extra low voltage (ELV) or on no volt circuits. That said, there is nothing stopping you using a mains voltage pump if required - the external relay detailed further on in this section is capable of switching mains rated loads up to 10A. If you do choose to use a mains rated pump please note my Disclaimer comments in Section 1 - Introduction.

If you choose to stick with the 24v water pump you are obviously going to need a plug in 24v power supply unit. I will touch on the safety implications associated with using mains rated pumps, and the additional protective measures required, in later blogs.

Hozelock Irrigation System Accessories

I have detailed the Hozelock range of accessories as they are affordable - expandable ... and what I currently use on my non-automated setup. There are many other systems out there , equally as good,  but this is where your preference comes in. For more information on Hozelock Irrigation please visit;

http://www.hozelock.com/watering/auto-watering.html

Before you rush out and start grabbing bits and pieces dont be deceived by the picture opposite - you will not need any form of time clock. The Cloud Scheduling detailed later in this project will be acting as your time clock.

You will however need 1) a pressure reducing valve - 2) the larger 10mm hose - 3) the smaller 4mm hose - 4) as many sprinklers, drippers etc that you need for your garden, and a Rain Sensor.The beauty of this system is that you can start out small and expand the system to whatever size you want.

Fixed Base Relay - 12v Coil With 230v (10A) Contacts

Rather than switching loads across the PiFace itself, in this project we will be switching loads across an external relay. There are however variants when you come to purchasing the relay;

11 Pin - This will give you 3 sets of Normally Open / Normally Closed contacts

8 Pin - This will give you 2 sets of contacts of Normally Open / Normally Closed contacts

The cost difference between the two relays is minimal. Although we wil only be using one set of contacts in this project it is worthwhile purchasing a relay that will give you means to expand in the future. I am using the 11 pin version. Manufactured by Europa Components - Relay Base Model Number is RB11R - and the Relay Model Number is R11R12D3PDT

You dont need to buy the exact relay but the schematic drawing that follows later in this project will detail connections for the above.

The Fun Stuff

In order to be able to control the Garden Irrigation System via an iPhone app and to enable Cloud Scheduling you will need the following in place;

     - an account with www.homeautom8.com (FREE)

     -  iAutom8 iPhone App (FREE)

     - an RFXCOM Transmitter (NOT FREE)

     - a Home Easy RF Device (NOT FREE)

If you dont want to go to the expense of setting up the RFXCOM transmitter with the Home Easy RF device at the moment, I will also show how to activate the irrigation system using just the rain sensor and manual switching when we get to this stage of the project.

A Twitter Account

Later in the project we will be reporting system status using the Twitter API.

To enable this you will need to create yourself a Twitter account. If you already have a Twitter account go ahead an create a new one dedicated to your Garden Irrigation system.

PVC Enclosure

Whilst you could always chuck all of the above components into a cardboard box and the irrigation system would work just fine - it would be a shame to have got to the end of the project and not have something worth putting your name to.

Wrapping everthing up neatly in an enclosure is a small price to pay given the work you will have put into the project

* Please note coder27 comments below