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TerryKing
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| Posted: March 04 2006 at 11:34 | IP Logged
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Is anyone using the "1-wire" interface (from Maxim-Dallas semiconductor) with PowerHome? I didn't find much with Forum Search. I'd like to connect both a 1-wire weather station and other 1-wire devices, because they're easy to wire over distances.
Any pointers??
Thanks!
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dhoward
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| Posted: March 05 2006 at 00:44 | IP Logged
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Terry,
1-wire is something Ive been wanting to add to PowerHome. Can you recommend any starter kits so I can evaluate what must be done?
Dave.
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TerryKing
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| Posted: March 05 2006 at 14:01 | IP Logged
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dhoward wrote:
Terry,
1-wire is something Ive been wanting to add to PowerHome. Can you recommend any starter kits so I can evaluate what must be done?
Dave.
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Hi Dave, I'm the guy in the Log Cabin from Vermont, from 3 years ago.. But now my wife and I are teaching in North Africa. We are back in Vermont in the Summer. I'm teaching robotics and electronics Over Here, and doing some work with the 1-wire LAN stuff.
I'll be back with another post soon after I have time to collect a decent set of pointers to 1-wire stuff. I've done computer interfaces of all sorts from the car-sized IBM 1800 to a 8-pin DIP, for, whew!, 32 years now that I think of it! Interesting, but That's Another Story... But the 1-wire network is one of the most elegant and simple interfaces I've encountered.
In a nutshell, Dallas Semiconductor(Now Maxim/Dallas) devised a brilliant way to put a variety of different devices on 1 wire. Usually a twisted pair is used, often CAT5 is used these days for longer runs. The devices CAN be powered from the signal wire, but often it's easier to run low-current +5V along with the signal conductors.
Each 1-wire device has a unique 48-bit permanent address lasered into it at the factory. So you can put, for example, many digital thermometers in parallel on one cable, and read them back separately. And they cost about $5 each, for .5 Degrees C accuracy. There are other device types too.
One early 1-wire example was a "1-wire Weather Station" which combined wind direction, wind speed and temperature. Today there are more full-featured low-cost weather stations on the 1-wire network.
PC's and Microcomputers can be interfaced to 1-wire pretty easily. There are USB and Serial "Dongles" that interface to 1-wire, and they are good choices if you want to use longer cable runs, as they control the cable waveforms to maximize reliability. The protocol includes a built-in CRC error-check on data coming back from 1-wire devices, so there's high data integrity.
Enuf for now; I'll try to get some pointers together, and find a good Circuit Cellar article too.
I'm just starting some kids on building a weather station with 1-wire, so I'll be On Subject for a while here.
Keep up the good work with PowerHome; the latest stuff looks real good. Now I just need more time to play...
Regards, Terry King ...On The Mediterranean in Carthage
Tunisia, North Africa
terry@terryking.us
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dhoward
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| Posted: March 05 2006 at 15:29 | IP Logged
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Terry,
This is great stuff. A very good post. I look forward to your followup.
So do you get a chance to use PowerHome while abroad?
Dave.
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onhiatus
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| Posted: March 07 2006 at 18:33 | IP Logged
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Hi Terry, welcome back for your visit. I spent almost two years traveling around Aftica - including several months in Morocco and a couple more in Egypt. The best thing about a visit home was just that it was a visit. Life is very different now.
Anyway, I use Peter Anderson's IOM #142A serial interface to talk to a number of Dallas temperature probes (DS18S20s I think). It provides an easy interface to the supported one wire components. I use a simple VB app to poll the probes and pass them on to PowerHome. I've never done much with the VB app as I figured I'd get around to rewritting it once PH supported plug ins.
Other advantages of the #142A are 4 controlled relays, and 4 optoisolated inputs. Neither of which I use right now, but they're there just in case... see details at http://www.phanderson.com/iom142/iom142.html
I highly recommend Professor Anderson's kits - the price is excellent for the functionality and I've found him to be very responsive (if short) to questions.
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dhoward
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| Posted: March 07 2006 at 21:22 | IP Logged
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Now I remember who had asked about 1-wire previously  . I couldnt quite put my finger on it and I hadnt had a chance to search back (pretty sorry when you're so busy you cant take 30 seconds to search your own messageboard  ).
I'll visit the Peter Anderson site again and order up a kit. With the new house and all, this is definately something that I would like to get into as well.
Dave.
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TerryKing
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| Posted: March 08 2006 at 16:02 | IP Logged
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More about working with 1-Wire... (Sorry, I Got Busy...)
Basically you need 3 things to try out 1-wire communications and devices:
1. A Computer-to-1Wire interface device.
2. One or more 1-wire devices to test.
3. Software to test with.
My suggestions would be:
1. The DS9490R: ($28) A USB bridge with 1-Wire RJ11 (Phone cable) interface to accommodate 1-Wire receptacles and networks. This is a thumb-sized adapter that plugs into a USB port. See:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3834/ln/
and get the .PDF file.
There is a similar 9-pin serial interface: ($29)The DS9097U is a sophisticated RS232 to 1-Wire adapter, which
performs RS232 level conversion and actively generates the 1-Wire communication signals. Together with an adequate TMEX software driver, it enables an IBM-compatible PC to directly communicate with any 1-Wire device connected to the adapter's RJ-11 port. See:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2983/ln/
2. I would get a couple of thermometer chips like the DS18S20 "1-Wire Parasite-Power Digital Thermometer". Look
at:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2815/ln/
and get THAT PDF file...
These devices are available online from Maxim-Dallas or Digikey.
3. To start with software, I'd go to:
http://www.ibutton.com/software/tmex/index.html
"1-Wire Drivers (Now Supports DS9490 USB!)". The 1-Wire Drivers installation package installs the drivers and demo software for all iButtons and 1-Wire devices. The full package includes the "1-Wire Viewer".
The OneWireViewer supports most 1-Wire features, including temperature, potentiometer, switch, A-to-D, humidity, SHA, memory, and data logging devices. There is a screen shot at:
http://www.maxim-ic.com/products/ibutton/software/1wire/OneW ireViewer.cfm
Anyway, it would be great to support both more complex devices like the Peter Anderson example, for added monitoring and control, as well as the off-the-shelf $29 USB to 1-Wire interface.
I'll try to keep up with what you're all doing...
PS: onhiatus, I like your handle. It's weird how you can get used to being SomeWhereElse than the USA, and how much a visit home can make you appreciate the freedom to express yourself, however stupidly and offensively, at any time..
__________________
Regards, Terry King ...On the Mediterranean in Carthage, Tunisia, North Africa
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TerryKing
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| Posted: March 08 2006 at 16:21 | IP Logged
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dhoward wrote:
Terry, So do you get a chance to use PowerHome while abroad?
Dave. |
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Dave, I am living in a house rented by the school we work at, so I don't have as high a need and ability to automate and monitor things. Plus, 220V X-10 is not popular here in Tunisia. There is an interesting possibility of doing some energy management stuff at the school, as a demonstration project. Hmm.. Maybe after we get a working Weather Station going...
Personally, I'm fine with X-10 for lighting, and turning the coffeepot on from bed in the morning, but I want more reliable communications to stuff like the furnace and water pump. My existing Vermont system is semi-industrial Opto22 stuff for the big stuff and X-10 for lighting only. If I had to start over today, I'd be running 1-wire for sure!
When I retire (lessee, that'd be the 3rd time...) to Vermont, I may redo a bunch of that.
What The World Needs is a bunch of inexpensive Optically Isolated 1-Wire input and output devices. And dimmers. Hmmm... I'm just installing 12 channels of 220V 10Amp dimmers at the school that are controlled over a DMX512 serial multidrop (RS485 levels) bus. Maybe if PH had DMX512 output... (See WikiPedia: DMX512 and also 1-Wire)
ALL this stuff could run on one CAT5 (See Wikipedia :-) cable daisy-chained around the home...
...we now return you to your previously operative fantasy...
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Regards, Terry King ...On the Mediterranean in Carthage, Tunisia, North Africa
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dhoward
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| Posted: March 08 2006 at 19:59 | IP Logged
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Terry,
Thanks for posting the links. Im going to look into this and probably order a few different things. Probably won't be able to spend much time on it until after the EHX show (end of this month) but will start on it right after.
Now hopefully I ran enough Cat-5e in my new house to be able to use the 1-wire stuff .
Dave.
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onhiatus
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| Posted: March 08 2006 at 20:40 | IP Logged
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Dave, The wiring for the one wire stuff couldn't be easier. I use cat-5 cables with 3 way splitters (one for the sensor, one in, one out) - it makes it VERY easy to add sensors. Even more fun - I crimp the DS18S20s dirrectly into cat5 plugs. I had a couple open taps and was able to add temp sensors that look pretty good by just sticking the plug into the wall jack... I know there's a total cable run limit due to the capacitance of the cat-5 cable, but I've yet to run into it - granted my house is small...
Terry, thanks (I have www.onhiatus.com as well - it's where I posted my travel blog before there were blogs). I always enjoyed the returns home when I was traveling - knowing I was leaving again made it much easier to overlook the things that bugged me. Of course the moving back for good (-ish) was a wicked adjustment...
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TerryKing
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| Posted: March 09 2006 at 08:56 | IP Logged
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onhiatus wrote:
| I know there's a total cable run limit due to the capacitance of the cat-5 cable, but I've yet to run into it - granted my house is small... |
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On(hiatus), the workable cable length on 1-Wire depends on how well the driver and interface control the pulse shape and timing. You can run up to a couple hundred feet with just a PIC type Digital IO and a 1K resistor pullup to 5V (A little stronger than 5k). But, the available (sounds like a car ad!) drivers and bridge chips from Dallas can greatly extend that by controlling the rise and fall time of the pulses, and sensing data at a non-TTL level at the optimum time. Some have had successful 1-Wire networks up to 300 meters (say 1000 feet) long.
The USB and Serial interface "dongles" mentioned in a previous post have such controls built in.
__________________
Regards, Terry King ...On the Mediterranean in Carthage, Tunisia, North Africa
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dhoward
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| Posted: March 09 2006 at 20:27 | IP Logged
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My biggest problem is that all of my Cat5 are homeruns (Ive got alot, probably about 200). I see that they make 1-wire hubs so you can setup a "star" configuration but these only seem to support like 6. Im wondering if you can feed a hub into a hub. Something like a 6 port hub into each of the 6 ports of a 6 port hub so I could have 36 1-wire devices.
Dave.
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onhiatus
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| Posted: March 13 2006 at 17:13 | IP Logged
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I'm not sure if I understand. Each device has it's own address, so you can put unlimited (well, I think 256 devices on a run). How the run is configured does not matter - it can be straight, a star shape, etc. just use a simple splitter to attach two runs.
So if I understand correctly, the 6 port hub should support ~1.5K devices. Unless the hub is just one run, in which case it should still handle 256...
Hope this helps. (Also hope I got it right).
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TerryKing
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| Posted: March 13 2006 at 17:29 | IP Logged
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dhoward wrote:
My biggest problem is that all of my Cat5 are homeruns (Ive got alot, probably about 200). I see that they make 1-wire hubs so you can setup a "star" configuration but these only seem to support like 6. Im wondering if you can feed a hub into a hub. Something like a 6 port hub into each of the 6 ports of a 6 port hub so I could have 36 1-wire devices.Dave.
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There's some complexity to the question... Ain't there always
Onhiatus, it's not just addresses, it's signal propagation, and reflections and timing...
Take a look at "Guidelines for Reliable 1-Wire Networks"
http://www.maxim-ic.com/appnotes.cfm/appnote_number/148
You may want to have more than one beer available when you start reading this. It's probably more than you wanted to know, but it's all there.
Dave, how LONG are the star sections?? You have 200 Cat 5 sections?? Where are you, IBM?? (Oh, no, that'd be Token Ring, right?  )
Hmmm. If they're all starred from some network cabinet / area, AND you're not already using the "other" two pairs in the CAT5, you could connect a longer out-back-out-back network that wasn't really a star.
I need to learn more about the hubs. If they are like the "Switched stub" example in the AppNote, they solve the problem. Maybe. Can you point to an example??
__________________
Regards, Terry King ...On the Mediterranean in Carthage, Tunisia, North Africa
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dhoward
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| Posted: March 14 2006 at 17:00 | IP Logged
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Terry,
Heh, not IBM...just a new house and tried to run as much cable as possible before the drywall went up. But yes, they all come back to a central wiring closet. That's a pretty good idea...I hadnt thought of using the extra pairs to send the signal back...effectively creating the daisy chain network. I guess then I just have to be concerned about length.
The hub that I was looking at can be found here: http://www.hobby-boards.com/catalog/product_info.php?cPath=2 3&products_id=33
Dave.
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Topic: "1-wire" interface to Weather etc.
