Growing my own produce is something that I have been thinking about for some time.  Now with the combination of the rising cost of fresh produce, combined with having a young family, it seems like the right time to start. Now I should point out that I am not doing this from a cost point of view, so I am not taking into account the payback period for setting up the system.  This will just be an added benefit over time.

Now, living in a fairly new residential suburb, we don't have a lot of space around the house for growing (although at approximately 250 m2, we have a larger than average backyard by today's standards). The lack of space, as well as the desire for ease of maintainability, is what initially led me to look at hydroponics. However, after speaking to a number of people on the subject, it became apparent that a hydroponics system would not meet my needs (primarily, to be able to grow a mixed crop). Further discussion then led me to investigate aquaponics.

Aquaponics is a combination of traditional aquaculture (raising fish etc in tanks) with hydroponics (growing plants in water).  In simple terms, the fish live in the water and produce waste. That water is pumped to the plants, where the plants absorb the nutrients, and the (now clean) water is returned to the fish tank.  For a more detailed explanation, refer to the Wikipidia article on aquaponics.

A traditional aquaponics system will consist of (at least) the following items:

• A fish tank to raise the fish
• One or more grow beds (which may or may not contain a grow medium, more on that later) for the plants to grow in

A system may also include the following items, depending on the configuration:

• A fingerling tank (for growing small juvenile fish) to project them from larger fish
• A bio filter or swirl filter (not always necessary)
• A sump tank
• Additional duck weed or marron ponds

On the subject of grow bed media, there are two main choices / types.  The first is to use a media-less setup, where the plants are grown in 'rafts' that float on the water in the grow beds, and the plant roots are suspended in the water.  The second is to use a media such as expanded clay or gravel.  The plants are then planted into the media much like you would in a traditional soil garden.

The bottom line is that there are many and varied system designs (both commercial off the shelf and home built DIY), and one can be built to suit your needs.

See the article on my aquaponics system for more detail on my specific setup.

In my discussions with friends about the system I am building, one question I have been asked repeatedly is whether such a system is cost effective. Another way of asking whats the payback period for the system.

Now I am building my system from recycled parts myself, and I am not building it with the intention of reaching payback at some point in the future,  but it is an interesting question none the less.

After some research I came across the following article on the Backyard Aquaponics website: Cost Benefit Analysis of Aquaponic System.

Written back in 2009, the paper was commission by a gentleman in Canberra looking to promote aquaponics locally.  It takes into account the the captial cost, as well as the running costs, of a number of off the shelf systems sold by Backyard Aquaponics.

While I haven't verified the numbers myself, after reading the paper I believe it covers the majority of costs involved and provides a reasonable estimate. For those not wanting to read the full paper, the answer is 2 - 3 years (depending on the size of the system). 

While your milage may vary depending on your system setup (as well as the changes to costs in 2011), it backs up my gut feeling based on my own estimates.

I decided to do a follow-up on my previous post about Electronic Tools to talk briefly about parts.

With regards to parts, this is one area where being a hoarder can be an advantage. I find that there are three main sources I use for components.  Firstly is to put an order in with a supplier like Element 14 or RS Components (there are others,  but these are the main two I use).  They are good because they carry a large range of components (and carry plenty of stock), you can order online (including free shipping in these cases), and provide fast turn-around times. The downside being that you have to plan and order in advance.

The second place I tend to obtain components from is one of two local retailers. In my case that's either Jaycar or Altronics. Being local it is easier to take a quick trip to the shops if I need something in a hurry.  The downside being that they have a far smaller range of stock.

The third place I will source components from (that can sometime easier) can be from other  old / broken electronics. As a habit now, any electronics that are broken / being thrown out I will disassemble and see what parts I can salvage off them.  The advantage is that I have a ready supply of various components that are alawys on hand for those cases where I need something over an above what I thought I would need in the original order.  It can also be a good time to practice your soldering / desoldering skills.

One thing I should mention is that, in electronics, there are two main categories of circuit components: Through-hole and surface mount. Generally when you are starting out in electronics, through-hole components can be easier to work with.  As you get more advanced, or the types of circuits you are building require it, you can move onto surface mount components.  (see the links for more details on the two types of technologies). In old equipment I am disassembling, through-hole components are generally easier to remove and reuse.  However, they are also becoming less and less common in electronics, as surface mount component have several advantages for large scale manufacture.

Just be sure that, regards of where you get your components from, you have a good storage system with good labelling.  Otherwise it doesn't matter how many components you have, because you won't be able to find the one you need.

As a part of a larger project I am working on at the moment, I have decided to invest in some new equipment for manufacturing / fabrication. This is the fifth in a series of posts where I will discuss some of the equipment I am looking at.

As mentioned in an earlier post, today I am going to talk about Electronics Tools.

When working on electronics, there are a few basic tools you should have.  At a minimum I would suggest:

• Multimeter
• Soldering iron (and solder)
• Side cutters

This will enable you to do basic circuit construction and repair.  Of course the following items will make your experience easier (and don't really cost a lot):

• Sponge (for cleaning the soldering iron)
• Solder wick and/or desoldering pump (for fixing up mistakes)
• Isopropyl alcohol (for cleaning up the finished PCB)
• Hook-up wire

If you are prototyping your own boards, or troubleshooting more complex boards, then the following may also be of use:

• Protoboard / Vero board / Strip board
• Logic analyser
• Oscilloscope
• Bench top variable power supply
• PCB design software
• Spare parts

Learning to designing your own circuits is a very large topic, and unless you're someone who has studied doing this, there is a lot to learn.  However if all you interested in is troubleshooting / repairing simple circuits,  or indeed building a circuit from a kit, then the top two lists will see you well on your way.

If you have any questions or suggestions, please leave a comment below.

Just for kicks, I decided to build an obstacle avoidance robot.  That is, a simple robot that will drive around, and if it encounters something in front of it, it will turn and drive in a different direction to avoid it. While this is a fairly simple start, my plan is to use this as a base and incorporate some more advanced functions as it develops.  But for starter it's a simple problem with a well understood solution.

Here are some early thoughts about the robot.

The robot is based around a three wheel design, where the front two wheels are driving, and the third rear wheel is just a castor for balance.

It will use an Arduino for control (just because I have one spare).

The propulsion will be from a pair of simple gear motors, using differential drive to turn.

As the wheels do not have any rotary encoders fitted, I may end up using a single axis gyro to detect the rate of yaw to help keep the robot in a straight line (and to help it turn). But i'll see how t goes without it.

For vision I am currently deciding between an ultrasonic ping sensor, and an IR sensor.  Again I haven't decided which I will go with.

I have drawn a quick model in OpenSCAD to try to illustrate what I am thinking.