On Mon, September 14, 2009 10:07, Nick Rout wrote: > I'd like to be able to gather and log some stats about my swimming > pool, and perhaps turn the pump on and off either remotely (via a web page > or similar) or automatically based on temperature (the pump not only runs > water through the filter, but also through the solar heater).
What data are you looking to collect? This is important as it dictates what kind of sensors you need, and therefore how complex the remote sensing unit will be. > Some of the data gathering points have no mains power close at hand, > and adding a wire back to the house would be a PITA. Really? Is it too hard to run a length of Cat 5e back to your Comms Room? I think you should split the problem into two parts, 'data collection' and 'remote control'. Arguably the first of these is quite simple, but you are likely to become overwhelmed quite quickly if you try to do everything at first. In my back garden I had a webcam, a temperature sensor and an anemometer. I built the anemometer myself from scrap, and I had a wind vane too, but I ran out of time to finish it. I also had a sensor on my council water meter. I logged a webcam snapshot every hour, and windspeed and temperature every 5 minutes. I queried the water meter every minute and logged new readings when they changed. I used a variety of technologies and tools (and you will undoubtedly get a lot of responses with an even wider variety) all Linux-based. IMHO you should start small (really small) and try to do one thing, such as the temperature of the swimming pool. This is a well-defined goal, and it's simple but you will have to learn a lot starting from scratch. Oh, and don't forget (as you start to build the system up) make sure the system protects *itself* from bad data and malicious/stupid command sequences (i.e. "run all pumps at full power and activate the drain valve" would burn the pumps out and flood whatever is after the drain). There is a good book in the library called 'Making Things Talk' by Tom Igoe, which discusses lots of techniques of hooking things up and getting data to and from them. Worth a read and you might find similarly useful books in the same section at the library. Best wishes, Andrew
