Remote temperature sensors - multiple sensors?

[The Natural Philosopher]

LMFAO.

Nice one.

[David.WE.Roberts]

...errrr.....a data wire but no clock signal wire? So asynchronous as opposed to synchronous data?

Or is it that it is assumed that data is only going in one direction, so the usual minimal TXD, RXD, GND (3 wire) configuration for asynchronous serial data (without any handshaking pins) is cut down to a single data wire plus earth?

If I remember my asynchronous communications (RS232 or V.24) which I probably don't after all these years then the signal was a voltage on the data line with respect to earth/ground.

I see from above a dedicated power line would be to power the remote device if it had no power source of its own. Taking power from the data line - not sure how this would work but I haven't looked at data comms for some years.

Cheers

Dave R

[The Natural Philosopher]

The audon one looks handy.

Id like that here.. to remind SWMBO to bring the hose in - especially the nozzle thing - when it goes below freezing. That's one a year she's broken.

By the way considering the OP was after shed monitoring, its worth pointing out that you can trail a 100m* of CAT5 and a LV power cable from a wall wart down under the garden easily enough inside a bit of e.g hose or the like.

I have to say that I am more and more finding all foirms of RF doint play nice with this house. Distances are too large and tehres to much metal in it.

Gimme cat 5 any time.

*The length limits on CAT5 are not an issue with a SWITCH as opposed to a HUB, because there are no collision possibilities down a single piece of duplex cable. 10Mbps is easily achievable over that sort of length.

[The Natural Philosopher]

well that depends on what is on the line.

It is a very simple very crude BUS system.

Not a pint to point bidirectional. Mire HPIB than serial ...

the data line is normally high. an 800pF cap in each slave stores charge when the voltage goes low..

Its designed to be very minimal, pretty slow and needs a master with most of the intelligence. In practice the master IIRC says 'hello XYZ address' and the slave says 'here I am and this is my value' and that's IT.

Cutting all power to all devices resets them. Neat huh?

[David.WE.Roberts]

Do you mean something like which looks interesting.

Cheers

Dave R

[David.WE.Roberts]

Don't recall saying it was for TMOAS - although that might be a possibility.

Also, I do have a partially implemented CAT5E cabling scheme to the shed and I also have mains power, water, and drainage.

At the moment I have an indoor and an outdoor (in the shade at the end of the garage) temperature monitor from Tchibo which works very well but I now want to monitor a couple of other places as well outside and two or three places inside (but not all the time).

It looks as though a 3 sensor package from Oregon might do most of what I want (apart from PC connection).

I think that the Oregon kit goes up to 8 channels in some cases, but starts to get expensive.

Now rapidly expanding my required reading as I Google more stuff.

Cheers

Dave R

[Andrew Gabriel]

distros for the Pi (e.g, Occidentalis) allow 1-wire devices to be connected to a GPIO, but I've got mine working off an I2C 1-wire bus master, which then makes the sensors available through a file-system interface.

The 1-wire bit-banging driver also gives you access via the filesystem interface (not that I actually like that filesystem interface).

[Man at B&Q]

es can derive enough power from the data wire to run without the power wire , but not all can. 1-wire refers to a single wire being used for data/signa l,

You are confused.

There are no end of protocols that embed clock (or other timing information) and data in the same wire.

MBQ

[Man at B&Q]

What's wrong with that?

Isochronous.

MBQ

[Jules Richardson]

Ah, that one would work, then. The upper limit's not a problem, but we can occasionally get down to -50C here, and the parts that I looked at wouldn't quite cover the lower limit while still giving a reading at sensible summer temperatures.

cheers

Jules

[Geo]

You may find that they have too wide a spread to be useful - I intended to display inside and outside loft temperature and humidity and bought three devices. The most closely matched pair (located at same point in loft) show nearly 20% difference:-

"Last data on 17/03/2013 at 13:50:17 GMT

Environment

Loft 5 °C 59 %RH Outside 6 °C 40 %RH "

Someone else found same result:-

[Windmill]

Is this perhaps overkill? One could hook ten cheap low-power silicon diodes in series, pass a more-or less fixed current through them via a resistor from a remote 12 volt source, hook it all up via twisted pair, thin coax, or whatever, and use a rasp or arduino to measure the voltage, which will vary with temperature. One doesn't need precision of 0.1C in most cases.