Remote temperature sensors - multiple sensors?

if you happen to have every room wired up with lots of ethernet cat5 ports/sockets, you can get modules that do environmental monitoring of server rooms and report back the temperature and humidity to a central monitoring PC.

Googling for temperature ethernet sensor yields:

if you're really lucky to have PoE on your network, you may be even luckier still to find temperature to ethernet modules that take power from PoE which simplifies installation and setup considerably.

We have got an old Tchibo one - still going strong.

And some Oregon ones - two base stations and three remote sensors. Mixed feelings. They work. But are not rechargeable-battery friendly. They don't like the lower voltage and/or outdoor temperatures. That is, they work for a while when freshly charged and at comfortable rather than cold temperatures.

Would like to have got decent kit and been able to connect to PC, etc. but could never quite justify it.

I am a bit surprised that there does not (yet?) seem to be available a nice little bluetooth temperature sensor - and a nice little price. Or have I missed them?

Did see this:

I use dallas 1-wire digital thermometers around the house. These are not wireless, and require a twisted pair to link them all, or 3 conductors, depending if they are driven in

You will need something to interface the Dallas 1-wire protocol to a serial port or a USB-serial adaptor. A raspberry pi can just about bit-bang the dallas 1-wire protocol with the 1-wire driver included in the Wheezy distro (which will only do a single 1-wire bus AFAIK, but you can have lots of sensors on it), and that's not very expensive. (It occasionally fails to read the 1-wire bus, but you can simply do it again when this happens.)

Before doing this I bought a bare 433MHz receiver with a view of decoding the Oregon Scientific signal, but I gave up trying to make that work. (I could see the transmissions on a scope, but they were very hard to separate from noise in software, and I didn't get as far as working out what the encoding was.)

There is also some info on doing it via I2c here:

In a similar vein, my house contains a small network of "2-wire" digital temperature sensors based on this design:

Any outdoor ones? When I briefly looked at this a couple of years ago, IIRC the Dallas parts were suited toward only part of the potential temperature range, so I was going to have to double up all the sensors (one p/n for colder temps and another for hotter) and read the 'best' one based on the time of year. I can't remember if they outright died beyond their limits, or if it was just that they were only accurate over part of the range.

cheers

Jules

Yes, and in the freezer at below -20C. The DS18B20+ does -55°C to +125°C. There are older part numbers with less range and/or less resolution (and most of mine are 10 years old, so are older parts).

Maxim/Dallas recommend you always use a separate power rail when using them at high temperatures, as the increased leakage in the package means their capacitor may run flat before completeing the temperature conversion when powered off the data line.

I've got a brilliant remote temperature sensor. Its called RAF Lakenheath & it tells me how cold it is outside via a widget on the computer :-)

Would one of those fit in me garden shed?

Won't, for example, measure the input and output temperature of the air going through my experimental heat transfer system.

Or the difference inside and outside the canopy over the veranda.

Various product write ups suggest that there may be a maximum of three wireless channels available at 433MHz - unless the industry standard chipset only supports 3.

If I was using wired sensors, I should have installed the wires during refurbishment as chopping in new wires now is not going to be popular.

Strange that there isn't a budget USB base station with (e.g.) 3 remote temperature sensors as you can buy the stand alone setup from Oregon Scientific for around £40.

Cheers

Dave R

Somebody gifted me a *remote thermometer alarm kit* made for and purchased from ASDA! (model no 41311) dated 06/08/11

The instructions say that pressing the *CH* button allows you to select a channel (1-3) giving you the option to poll 3 outdoor sensors. There is a miniature jack socket on the sender enclosure but no explanation of any purpose

This implies that the remote sender is available separately.

The unit looks very much like other Oregon Scientific stuff I have but maybe a knock off?

Am I the only person trying to work out how "1-wire" means twisted pair?

Andy

On Wednesday 06 March 2013 09:51 Andy Champ wrote in uk.d-i-y:

The name is erroneous - a marketing gimmick - it means "1 wire for +ve power and data combined" - you still have a 2nd wire for ground...

I too had forgotten what that was about. Thanks.

ndy Champ wrote in uk.d-i-y:

Not that this is any particular help to the OP, but there's a small module on the market that gives you a serial signal of T and RH - DHT11. They just a bit over a quid each. I don't have the spec in front of me at the moment so I don't know what temperature range they go to. It's a 4 lead device about 10mm square. I'm about to couple a group of them to an Arduino to see if I can cut down the what seems excessive underfloor ventilation here.

Rob

No.

Ive got another remote temperature gauge that's also brilliant. Its attached to the oil tank. It's supposed to tell me how much oil us there, but below -2C it simply stops working. :-)

No what it means is it only needs one port pin on the processor, but still a gimmick in the wording I think. I have two of these sitting next to my sandwiches at the moment. Note that they have 3 pins too ;-)

There are actually three wires! Ground, data and power. Some 1-wire devices 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/signal, unlike other hardware protocols which require data + clock at least.

I've got multiple 1-wire temperature sensors hanging off my Raspberry Pi. S ome distros for the Pi (e.g, Occidentalis) allow 1-wire devices to be conne cted to a GPIO, but I've got mine working off an I2C 1-wire bus master, whi ch then makes the sensors available through a file-system interface.

dan.

Prolly needs oiling.