All valid questions. Consider this, however – let’s say, for the sake of argument, that you were just now getting into home automation. You really like the idea of building up a dataset of what’s happening in your house – how often doors are left open, lights are left on, etc. You want to make sure that lights are never left on in unoccupied rooms; you have a feeling that this happens a lot, but you really don’t have any proof. Say you want to know just how hot your attic gets in the summer, and whether or not that is a contributing factor to why the upstairs of your house feels like a bloody toaster in August.
So you start looking at available solutions, and boy are there plenty. 1-Wire devices are really popular with the hardcore DIY crowd, are reasonably cheap and well-supported by the community. Good deal. Then you remember the lighting issue – 1-Wire doesn’t really do mains-level voltages. Well, not safely anyway – you really want something UL listed, so if it goes nuts and burns the house down you have some recourse and the insurance company will actually make good on those premiums you’ve been paying for the last 20 years. Back to the drawing board and more research – no shortage of stuff here. Your dad’s old buddy X10 is still around (complete with AMAZING BLINKING TEXT ON THE WEB PAGE), but if memory serves X10 sucked back in the day and based upon a bit of research you determine that it STILL blows. OK, scratch that. Insteon looks cool, you say – and the folks on the Misterhouse team really like it (if they are not still using X10, that is). Smarthome apparently has spends a fair bit on advertising, because you see Insteon ads EVERYWHERE. so you go and buy some sample devices – hey, they work pretty well, aren’t too unreasonably priced, and have a large selection. You decide to do some forum posting letting folks know that you’ve finally found the answer, and receive an almost immediate response – “Don’t do it, man! I just got done ripping the last of the Insteon crap out of my house!” Apparently folks have issues with reliability of the devices – switches that just stop working, motion sensors that unexpectedly freak out, and so on. Further probing shows that this is hardly an isolated case. Crap, back to the drawing board. You go back to the initial informant and ask what he’s replaced it with – and he answers “DMX” or “KNX” or some other solution which would require you to take out a second mortgage. No thanks.
This leaves three valid contenders: Z-Wave, ZigBee, and UPB. Of the three, Z-Wave currently has the best traction in terms of price point, reliability, availability of devices, and interoperability. Z-Wave is also a standard, meaning that devices from one vendor will (in theory) work with those from another vendor. Oh, and you discover that there are several devices commercially available that not only provide device control (dim, switch, etc) but also provide power usage at the device level; motion detectors that also report temperature, light level, and humidity, etc. Good deal. More questions to the peanut gallery indicate that people have been pretty happy with the technology overall, and that reliability seems to not be an issue. As an added bonus, it is an RF-based mesh networking technology, so the more devices you add, the more reliable the devices get (again, in theory). New devices are added all of the time, and they are available everywhere, even Home Depot, Amazon, EBay, and a plethora of other online stores. If anyone is interested I can share a list of the places I’ve had good luck purchasing from (and which vendors to avoid)
As for UPB, the devices are out there, but are seriously expensive – $135 USD for a single dimmer switch? Ludicrous. Plus it’s still a powerline signal-based solution, subject to all of the noise and interference that plagues X10 and (apparently) Insteon. It’s a non-starter.
What about ZigBee? Very promising, but device support just isn’t there yet. Lots of chatter on the ZigBee Alliance page, but a quick googling only turns up a couple of online sources, neither of which shows any actual prices for the devices. Doesn’t exactly inspire confidence.
OK, so we’ve got 1-Wire for environmental sensors and Z-Wave for lighting control. Easy enough. Then you stumble across Rob Faludi’s book Building Wireless Sensor Networks and decide to check it out before completely buying in to 1-Wire, and he makes some really compelling points – sensors should be reasonably inexpensive, fairly simple, and wireless so that you aren’t constrained by cable lengths or pulling new wires to add a sensor. Building them yourself opens up a whole world of possibilities; need a sensor that measures temperature, light level, and humidity in one room? An XBee, an Arduino, and couple of discrete components and you’re done. Later decide that it would be really nice to add a moisture sensor to that same device to check the soil moisture in your African Violet? Buy the sensor, plug it in, update the code and you’re set. Unconstrained by the commercial sector and whims of the consumer, you can build the sensor(s) that you want, place them where you need them, and upgrade them to your heart’s content.
At this point I’m going to switch back to first person, because I’m tired and writing in the 3rd kind of sucks.
I picked up a couple of XBees, a couple Arduino FIOs and some sensors from SparkFun and put together a few sensors. Nifty little devices, about $50US for each sensor after the parts are included. I also bought a ConnectPort X2 from Digi based upon the recommendation in Rob Faludi’s book – it’s an awesome device, and it essentially means that I don’t have to pick up a Windows license to update or change firmware on my XBees; firmware can be updated wirelessly from a browser, which is a REALLY nice feature when you have sensors stuffed in an attic or somewhere equally unpleasant.
Which brings us back to the original question – why HomeHeartbeat? It really comes down to cost, capability, and convenience on my part. I picked up the sensors for $5 USD each on EBay with free shipping; one of my custom XBee-based sensors costs upwards of $50 USD. For that $5, I get a well-integrated, battery-powered, mesh-networked sensor running a well documented protocol (ZigBee). My gut tells me that the sensors themselves are all the same basic device – similar form factor, all 3V CR123 lithium battery-powered, same radio, etc. I’m dying to crack a couple of them open, but I’ll have to wait for my toPrecision Torx Screwdrivers to arrive from Amazon to check, as they are held together by tiny little T3 or T4 screws. If I find what I expect to find, and am able to decode the protocol adequately, I should be able to build some pretty cool additional sensors using the HomeHeartbeat devices as a starting point. I’ve got no doubt that I’ll be able to decode the protocol, the tricky bit will be designing sensor circuits which will operate within the voltage constraints of the sensor and provide useful information. If I can manage to implement a light, humidity, temperature, and motion detector sensor within a single device I’ll be a very happy camper