It seems everyone is building home automation projects with these cheap ESP8266 boards. So am I.

This is mostly a pointer to the github page where all the source is available as well as general instructions. You can build it yourself from that if you’re so inclined. But the instructions don’t tell you what to use it for so I can add that here.

I have half a dozen possum traps scattered around the house. Possums, where I live, are a serious pest and we do everything we can to get rid of them. The traps are kill traps and quick enough to be humane, I don’t like animals to suffer, but I’ll still kill them.

So the main purpose of this project is to build little battery powered units that send a message to a central server when the trap goes off. The traps go off with a bang, enough vibration to set off a mercury switch and that triggers the message send. Messages are logged on the server and I can check the log from any of my wifi devices by browsing to the right location. This is useful for two reasons.

First, I am interested in what time of night I am most likely to trap a possum. This is just curiosity about their habits.

Second, the traps are all positioned where I can easily see them at the moment. I live on the edge of the forest and I would put some of them down there if I knew I would check them. So this will help. Of course there is a range restriction for the wifi signal but it seems to get at least 30 metres with line of sight.

But there has also been some scope creep. The same unit can also tell me if mail has arrived at my letter box, which is quite a walk from the front door. Another can tell me about visitors arriving, something we don’t always see from the other end of the house. Those two need something more than a log to check later, they need a siren. So I rigged a small siren up to the Beaglebone home server I have. When a message from the mailbox or driveway arrives it logs it as usual but also sounds the siren. Apart from breaking out the mercury switch on the letter box to position it better, all the remote units are exactly the same.

The units are quite small, I’ve built them into a 3xAA battery holder, slightly modified because I need 2xAA batteries and the third battery space is for the electronics.