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"1-wire" temperature logging etc.

Gina

By Gina
in DIY Astronomer

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Gina

Gina

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I've also posted this in the Concrete thread but thought it could do with a thread of it's own as it has many other uses too including a complete weather station. I shall be using 1-wire temperature sensors (and possibly control) for my DSLR cooling project.

It's a couple of years since I last looked at 1-wire and I'm a bit rusty on the subject. I want to get back into it as I want to monitor temperatures and control devices for my DSLR cooling project. I also would like to get back to my 1-wire weather station.

I've been searching my bookmarks and Google for the information and this is what I've come up with...

Main support site for 1-wire :- http://www.1wire.org/

Suppliers :-

Software :-

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Reggie

Reggie

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Hi Gina, How are you hooking up the one wire devices to the linux box? Are you using a usb dohicky or do you have another method? I talk to mine through an arduino usually, custom software is very easy to use/write, using the 'processing' language you can write for pretty much any OS.

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FraserClarke

FraserClarke

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I've been using the one-wire stuff for temp (and humidity) monitoring for the past year or so -- been very happy with it all. I have a usb dohicky on both linux and windows systems.

Will definitely use it as a relative cheap temp monitoring system in the future.

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Gina

Gina

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Hi Gina, How are you hooking up the one wire devices to the linux box? Are you using a usb dohicky or do you have another method? I talk to mine through an arduino usually, custom software is very easy to use/write, using the 'processing' language you can write for pretty much any OS.
Actually using a RS232 (serial port) 1-wire adapter ATM. Just using OWFS as interface which makes all 1-wire devices look like folders and files. Very simple to use. I write my software in Python but any programming language could be used. Python is free GPL software and very flexible.
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Gina

Gina

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I've been using the one-wire stuff for temp (and humidity) monitoring for the past year or so -- been very happy with it all. I have a usb dohicky on both linux and windows systems.

Will definitely use it as a relative cheap temp monitoring system in the future.

Yes, it's so remarkably easy isn't it? :( I have a full weather station using 1-wire - temperature, humidity, wind speed and direction, rain gauge, daylight level sensor. Not quite fully finished yet. I've done all sorts of interfacing in my time and 1-wire is so much simpler than anything else :)
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JamesF

JamesF

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I found the USB<->1-wire interface can be a bit sensitive to line length. I had more success with a "proper" serial interface (ie. not USB<->serial), and even more when I added a power injector so I wasn't relying on the PC for power at all.

The Arduino 1-wire stuff looks interesting as it would mean the 1-wire bus could be kept short and the data routed back to a central hub over ethernet. Last time I looked it appeared to be somewhat incomplete, but I'm not averse to adding the code for devices that it doesn't yet support when I have the time.

James

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Reggie

Reggie

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You know, I'm sure I saw a circuit for ds18b20s chips that was just connected to a serial port somewhere......

http://www.hoppie.nl/tempsens/

https://decibel.ni.com/content/docs/DOC-1092

http://lookass.ch/content_files/dthowto.txt

http://groups.google.com/group/digitemp/browse_thread/thread/f6092ca9de727577

Some of them seem a little old (still using rs232 and not usb to serial ttl) but I suspect we could build something with an ftdi, the groups.google.com link seems to hint that it's very possible and the lines don't need inverting.

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Gina

Gina

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Thanks for the links Reggie - had a quick look and will go through them later :(

My Linux boxes are quite old and have RS232 serial ports.

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JamesF

JamesF

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Older machines with real serial ports are a definite advantage. It's a real shame modern motherboards don't tend to have them, or push them through a USB interface if they do.

James

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Gina

Gina

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You still have to be careful with those, Gina. I've got a couple that present as USB internally which is somewhat frustrating.

James

Really?! That's a bit much! :( Never tried one myself.
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Reggie

Reggie

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If anyone is really that bothered about ttl vs rs232 and inverted signals, then buy an ftdi ft232R based device and get yourself a max2322 chip (think that's the number), then you have the best of both worlds, 3.3v/5v ttl signals for arduino, pi, <insert random dev board here> and you also have the rs232 levels and signal polarity sitting up nicely for the old tech.

The one that I am reallly missing is the parallel port, from time to time I find projects that are incredibly useful but only accessible via a real parallel port, lucky for me I've got an old laptop with a pport on it and a dual core amd machine.

Oh, nearly forgot, the ftdi dongles already talk i2c etc. via their api.

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Reggie

Reggie

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Ha, I did forget something. If you are using a pi to talk to 1-wire devices, then you're not going to need rs232, in fact, you're probably not going to need anything extra except maybe a resistor. Pretty sure the pi can talk 1wire and I know for sure that it's already got tx/rx pins exposed, I think it's 3.3v, if that's the case and the dallas chips are 5v then you'll probably need 3 resistors :(

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yesyes

yesyes

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Does anyone happen to know exactly where on its TO-92 housing the DS18B20 is measuring the temperature?

I'm using them for my DSLR cooling project. I've put them with the flat side on the cold finger and used a small metal bracket to fix the sensor in place. I got a temperature reading of around +5 degrees C but I did see ice forming on the cold finger right next to the sensor.

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Gina

Gina

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I don't know the answer to that Chris. I expect its in the middle of the plastic case but no idea really. I'm also putting the flat side against the cold finger but have the whole thing in thermal paste. Same thing with the intermediate plate and the water block. I'm monitoring all three points. I might add one for the ambient temperature in the scope room too - I still have a few left. Adding sensors is only a matter of running a twisted pair cable as required.

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  • 2 weeks later...
Gina

Gina

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The sensors are already calibrated as they come - accurate to 0.5 degrees C. This is twice as accurate as a mercury thermometer.

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rcheshire

rcheshire

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Sorry. I'm being a bit too minimalist with my question. I like the idea of 1wire and would like to know the outcome of the temperature readings. Clearly, +5 and ice is not quite right. AFAIK any flat side will do for measurement.

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yesyes

yesyes

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Sorry. I'm being a bit too minimalist with my question. I like the idea of 1wire and would like to know the outcome of the temperature readings. Clearly, +5 and ice is not quite right. AFAIK any flat side will do for measurement.

I guess this is referring to my question earlier.... :)

In the meantime I found a way to make these measurements more exact. I cut strips off 0.3mm copper sheet and folded them around the sensors, filled with heat transer paste, as shown in the attached photos. I'm now getting a reading of -9 °C directly next to the cold side of the peltier.

post-2143-0-69220500-1339435240_thumb.jp

post-2143-0-08182300-1339435272_thumb.jp

post-2143-0-16831000-1339435304_thumb.jp

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Gina

Gina

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You can't do better than that Chris IMO :) That was what I was thinking of for the sensors. Just that I haven't got any copper thin enough - guess I should buy some :D

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