I have recently been working on a DIY gadget to allow remote monitoring of the status of the leisure battery which powers our electric chicken fence. Usually the first warning that the battery is getting flat is a red warning light on the fence energiser. By the time we see this it is normally too late and the fence is not being powered at an effective voltage. This is not an ideal situation, with foxes visiting our garden most nights. The idea of the remote monitor is that it will always give an accurate reading of the battery voltage, that can conveniently be checked from inside the house and can sound an alarm if it drops below a predefined threshold. It will also give an indication if the electric fence is actually switched on. There is a switch for the fence that we use to power it down when entering the run to collect eggs, etc. Unfortunately it is all too easy to forget to turn the fence back on when finished. Without going back outside it is often not possible to see if the fence is on or off. The energiser does have a light that flashes green when the the fence is powered, but this is not really visible during the day. As an additional feature the outside temperature is also monitored. To be honest a large part of doing the design was as a challenge to do something different and interesting during the winter evenings. But I do still think it will be a very useful tool to have.
I have now produced a fully working prototype. It consists of two units. A transmitter unit that sits near the bottom of the garden, connected to the battery, monitoring and regularly transmitting its readings. A second unit in the house receives the data from the transmitter and displays the status on a small 16×2 LCD display. Both modules are based around an Arduino Duemilanove microprocessor board. The Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. There are plenty of free resources available that make the Arduino platform an easy introduction to microprocessor development. The Duemilanove is the latest revision of the basic Arduino USB board. It connects to a computer with a standard USB cable and contains everything else to program and use the board. For the wireless link I used low cost 433MHz AM Transmitter and Receiver modules. With a couple of home made antennas the indoor receiver unit can reliably receive data from the outdoor transmitter when separated by more than 40m (and a window).
To finish off the design and get it into daily use I just have to box the two modules (including a weatherproof box for the outside unit). I also need to ruggedize the antennas and have a couple of minor hardware and software tweaks that I would like to implement. In the spirit of the open source Arduino platform that the design is based around, I am happy to share my design. If anyone is interested drop me an email (on the Contact Us page) and I will write up the project and provide a link on this site to any support files I have. I am sure that the general design could be used for numerous general purpose remote monitoring or control applications. With small software changes, for instance, the receiver could support multiple transmitter modules.