Elp-hay me on my sensor network

Hair brained plans galore! I am planning on flooding my house with environmental sensors. Temperature for starters. All over the place. And of course I want my readings to be gathered on a central machine. Live. So, no data logging on separate memory chips. I need some sort of network. With wires and stuff, because I do not trust the airwaves for this sort of thing. Also, I am a cheap skate.

So my list of requirement looks a bit like this:
- thin two-wire cable(s) running through my house
- multiple sensor units hooked up to this cable (parallel)
- each sensor sends digital data over the cable to a central master unit

My wild idea so far extends to this:
- one little MCU on each remote sensor unit
- very little power consumption by sensor units
- power comes through cable from central unit
- sensor unit stores power, in super capacitor, I suppose
- central unit detects when voltage level peaks on the power bus
- then shuts off the power
- sensor units detect high power level (well, they simply boot up because of supply power coming on)
- sensor takes reading(s)
- one by one sensors dump their readings on the -now data- bus
- sensor dies of lack of supply and the cycle repeats when master wants a new reading


Challenges as I see them so far:
- making simple and cheap sensor units so I can sprinkle them around the house
- have up to, dunno, twelve of them on one bus
- all talking on the same line without colliding data packets
- talking on a data line that has a massive capacitor nearby and a dozen more all around the bus
- driving a data line with only the power from one 1F/5V charge, long enough for the transmission of a few bytes

All and any ideas are welcome. Feel free to denounce my plans. Alternatives are also welcome. Keep in mind: I don't really NEED this network. I just like to build and operate one.

I don’t know if this is

I don’t know if this is cheap enough for you but you can but I think you can put up to 64 thermosensors on one bus with Dallas one-wire temp sensors. They’re a little bit of a pain in the ass but they have a lot going for them IMO. I got four samples from Maxim to see how they are. Maybe you should check them out.

Interesting read

Another datasheet on my to-read-list. Will study this protocol and its “parasite power” feature. I wish I could rebuild that power thing alone, so I could use it for all my sensors: humidity, electrical power meter, gas meter, wind meters, door sensors, sun sensors, what have you.

Rik presence sensors!

This might be helpful?



Great find!

That’s really awesome. Thanks Geir. This pdf is very comprehensive reading material. I am just about to wrap my mind around “Schottky diode bridge rectifiers”.

Bad ass. Thanks for feeding

Bad ass. Thanks for feeding my mind.

Dallas One-wire no go with PICAXE

I figure you’re not going down this road anymore but I wanted to say that I found the PICAXE is not able to keep up with the one-wire interface. That screws up my agenda. I just wanted to stop others from making such plans.