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Thread: First steps with 1-wire sensors?

  1. #1
    Automated Home Jr Member Simon300's Avatar
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    Question First steps with 1-wire sensors?

    Hello

    I'm looking to use 1-wire for temperature sensors as the first step of an HA project (see earlier).

    I have a solar cylinder with pockets for temperature measurement which extend about 10-15cm into the cylinder. Any sensors will have to fit alongside the boiler controls (e.g. one is a sensor probe, a bit like Ruggedised Temperature Probe).

    So as a first step I'm looking for 1-wire temperature sensors that can be installed in the top, middle and bottom pockets of the cylinder. These pockets are sealed on the outside (with some kind of rubber bung) and could reach up to 90C.

    So, my initial questions are:
    1) Who are people's favourite 1-wire suppliers in the UK? There's a thread here but it's quite old now. I'll need a retail suppliers, not trade account only.
    2) What is the most suitable temp sensor for this use? The ruggedised probe above is 28 each so not really viable - can I make some sort of cover/sleeve for a DS18*20? I suppose if they need replacing periodically that wouldn't be a problem if they were relatively cheap.

    As for control etc that will have to wait for another day (week/month!) - the main thing is to get the sensors installed along with the cylinder (the week after next). Of course ideally I'd like to be able to test them so have considered one of those 1-wire to USB interfaces. Ultimately I think I'm aiming to get 1-wire -> (Ethernet e.g. opn-one) xAP -> O2 Joggler but that seems a long way off at the moment.

    Any advice or pitfalls (1-wire layout looks like a common one) would be most welcome!

    Simon

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    Moderator toscal's Avatar
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    Apart from the Maxim site I only know of these places for 1 wire products and info.
    http://www.audon.co.uk/1-wire_modules.html
    http://www.homechip.com/catalog/ you have already discovered this one.
    http://www.1wire.org/

    Unless its only 2 sensors on very short runs try not to go down the parasitic power route.
    1 wire devices have three wires or connections Ground, Data and power. In parasitic mode the power connection is not used. And from memeory I think its connected to ground.

    For more general info the Maxim website is very good.
    Guidelines for 1 wire networks

    You may be able to get a couple of free samples from maxim. Use this link
    Last edited by toscal; 14th August 2010 at 10:17 PM.
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  3. #3
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    Quote Originally Posted by Simon300 View Post
    Hello

    I'm looking to use 1-wire for temperature sensors as the first step of an HA project (see earlier).

    I have a solar cylinder with pockets for temperature measurement which extend about 10-15cm into the cylinder. Any sensors will have to fit alongside the boiler controls (e.g. one is a sensor probe, a bit like Ruggedised Temperature Probe).

    So as a first step I'm looking for 1-wire temperature sensors that can be installed in the top, middle and bottom pockets of the cylinder. These pockets are sealed on the outside (with some kind of rubber bung) and could reach up to 90C.

    So, my initial questions are:
    1) Who are people's favourite 1-wire suppliers in the UK? There's a thread here but it's quite old now. I'll need a retail suppliers, not trade account only.
    2) What is the most suitable temp sensor for this use? The ruggedised probe above is 28 each so not really viable - can I make some sort of cover/sleeve for a DS18*20? I suppose if they need replacing periodically that wouldn't be a problem if they were relatively cheap.

    As for control etc that will have to wait for another day (week/month!) - the main thing is to get the sensors installed along with the cylinder (the week after next). Of course ideally I'd like to be able to test them so have considered one of those 1-wire to USB interfaces. Ultimately I think I'm aiming to get 1-wire -> (Ethernet e.g. opn-one) xAP -> O2 Joggler but that seems a long way off at the moment.

    Any advice or pitfalls (1-wire layout looks like a common one) would be most welcome!

    Simon

    I have bought some from ebay - either http://cgi.ebay.com/Digital-Thermal-...efaultDomain_0

    or http://cgi.ebay.com/Digital-Thermal-...efaultDomain_0 - I cant recall which one. Its sealed into a stainless looking probe thing with a hard black compound that might be epoxy or something.

    I havent installed them yet, as they are for the pools intake and outlet water so I have to do some plumbing etc to get them in place, but they look ok.

    Probably wont get there in time tho.

  4. #4
    Automated Home Jr Member Simon300's Avatar
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    Quote Originally Posted by richms View Post
    I have bought some from ebay - either http://cgi.ebay.com/Digital-Thermal-...efaultDomain_0 or http://cgi.ebay.com/Digital-Thermal-...efaultDomain_0 - I cant recall which one. Its sealed into a stainless looking probe thing with a hard black compound that might be epoxy or something.
    ...
    Ah, yes - they look just the job (I hadn't found my way round the part numbers yet). Maybe I'll put in an order in and cross my fingers (it's not that critical if they're not installed at the same time - it would just be less of a faff later).

    Thanks too to toscal - yes, I'd thought I'd better include the separate power conductor from the start too. Also your link to http://www.1wire.org/ led me to DIY Zoning Project which is exactly the sort of thing I'm trying to do next

    How about cable? I'm sure I read somewhere about a 1-wire specific cable (smaller than CAT5 perhaps), though now I'm wondering whether I should buy some Clipsal pink CAT5 instead. My reasoning is I'll want to put sensors in other places in the house eventually, I could later replace the 1-wire stuff with C-Bus or IDRATEK and I need some new cable as I don't want to use my heavy/inflexible CAT6A stuff on this. Plus, what connectors do you generally use? RJ45 or RJ11? (RJ11 would be neater but maybe I would struggle to fit a CAT5E sleeve into the plug)

    Thanks again!

    Simon

  5. #5
    Moderator toscal's Avatar
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    Personally I would run at least cat5 cable.
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  6. #6
    Automated Home Legend TimH's Avatar
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    Quote Originally Posted by Simon300 View Post
    How about cable?
    I've got some of mine soldered to alarm cable (smaller diameter than cat5) and I then convert to Rj45 / Cat5 once I'm "away" from where the sensor is installed. Alarm cable is (should be) stranded and already tinned so soldering is quite easy

    Definitely run some Cat5 to the room / cupboard where the cylinder is though as well.

    HTH,

    Tim.

  7. #7
    Automated Home Sr Member MrFluffy's Avatar
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    I did my last house in parasitic mode with cat5 for the wire, but I used one of these :-
    http://www.ibuttonlink.com/link45.aspx
    It was bombproof, the only time the network gave issues was when there was a physical short on the bus, which brought the entire bus down of course until the short was eliminated.
    I bought all my ibutton stuff direct from the states, it was cheaper than messing round. Ive got a bag somewhere of ds1820's to use on this place as I bought loads as they worked out so cheap that way (2.85 a sensor from looking at a old receipt).

    In fact Im going to rescue it from the other house and fit it this one in a few weeks as we're replacing all the intelligent house stuff in there with dumb COTS products and the heating control system is being replaced by some dumb wall mounted bendy wire thermostats. Because at the end of the day having stupid old fashioned stuff controlling things that the estate agent can understand puts more value on your house when you sell it

  8. #8
    Automated Home Jr Member Simon300's Avatar
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    Quote Originally Posted by MrFluffy View Post
    I did my last house in parasitic mode with cat5 for the wire, but I used one of these :-
    http://www.ibuttonlink.com/link45.aspx
    It was bombproof, the only time the network gave issues was when there was a physical short on the bus, which brought the entire bus down of course until the short was eliminated.
    I bought all my ibutton stuff direct from the states, it was cheaper than messing round. Ive got a bag somewhere of ds1820's to use on this place as I bought loads as they worked out so cheap that way (2.85 a sensor from looking at a old receipt).

    In fact Im going to rescue it from the other house and fit it this one in a few weeks as we're replacing all the intelligent house stuff in there with dumb COTS products and the heating control system is being replaced by some dumb wall mounted bendy wire thermostats. Because at the end of the day having stupid old fashioned stuff controlling things that the estate agent can understand puts more value on your house when you sell it
    Thanks for the thoughrs Mr Fluffy.

    A quick update: I've received 3 DS18B20 temperature probes from Ebay (from Hong Kong) - I'm not convinced the sleeving is high temperature like the "proper" stainless items, but they were much cheaper, look neat enough and fit nicely into the temperature pockets on my DHW/solar cylinder. I have ordered a roll of pink C-bus CAT5E cable from http://www.gil-lec.co.uk/ as I don't want to use my fancy network cable for 1-wire, plus it could also be upgraded to Clipsal or IDRATEK later. Finally I spoke to Nigel at HomeChip who was very helpful and advised me to buy a Link USB (which is a Link 45 with a USB converter on the front & more reliable than the DS9490R apparently).

    I haven't decided whether to use RJ12 or RJ45 plugs/sockets yet. I am ultimately expecting to have about a dozen or so temp sensors and so for the ones in rooms I'm planning to run the DQ/GND lines "down" one twisted pair (to a DS18B20 the back of a faceplate) and "back up" another in the same cable so that the sensor is not on a branch. I thought about buying a load of RJ45 or RJ12 couplers that I could open and solder the drop cable into (if you see what I mean!).

    I take your point about removing HA stuff if you want to move house. I think the lack of standardisation in HA is a real challenge at the moment - almost whatever you do will end up being home-grown. My plan is to use 8 port UFH manifold (or maybe two 4 ports) with 24V actuators and probably a 8-channel DS2408-based unit (http://www.hobby-boards.com/catalog/...oducts_id=1554). If necessary you could just remove all the actuators and leave all zones permanently on. Control software is still a bit up in the air though...

  9. #9
    Automated Home Sr Member MrFluffy's Avatar
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    What I did in the old house was to strip out the computer, the 1wire bus and just common all the individual rooms into two zones and fit two std wirsbo area thermostats and a wirsbo psu/relay unit which could control all the zones as two common ones. 160 all in. The facia's, sensors and wiring are still there for the individual rooms but its up to whoever comes along afterwards if they have any HA interest to fit their own gear or not. The lights we've left as x10/wireless as its star wired to suit, and going back to a conventional lighting setup would involve a complete rewire of the lighting with all the disruption to decor etc that involves.

    It guts me to have to remove a system which worked flawlessly for 9 years now, datalogs going right back, individual room temperatures with time of day mapping etc. But, as the agent pointed out, people allegedly don't want all that sophistication, they just want a knob on the wall.
    This time we're doing it backwards, in that we've rewired standard so we can get the electrical rubber stamp on it all, but ran the extra cables in for HA alongside and cat6 stp into blank boxes alongside the switchboxes etc, and when we get the cert for the install we'll automate everything we can as a retrofit. BUT, in future if we decide to move and the above scenario plays out again, we can just revert to the original "normal" setup by removing all the intelligent stuff, as the copper for it etc is still there. I think thats the best of both worlds. The ducts and cables are all there if someone wants them, but if they dont itll just work as a normal house, so if you have a ha enthusiast the ducting is a selling point also...

    If you think about it, if its not something a electrician or plumber can fix with a hammer at 2am, then the majority of people will be mortified by the prospect of "what if it goes wrong" and you'll loose potential customers to buy the house. And the smaller your target customer market, the worse the price. So at this stage of the game of HA development I'd caution people to put some thought into this side of it too. I read in the states that a big part of the HA market is retrofits both with better technology and to remove it completely, and new companies have sprung up specializing in that field to cater for it all.

  10. #10
    Moderator toscal's Avatar
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    Have to agree with you there MrFluffly. Many people suffer from technophobia when it comes to HA.
    The way I look at it is, if my mum can't operate it then its too complicated.
    Mind you I have seen some new builds with so called HA built in, if you can call it that. All it was was a re-badged alarm panel probably Visonic, that shut the water off if there was a leak and turned the gas supply off if there was a fire. Oh and for a rather extortionate price you could also have the ability to turn off the ACs when the system was armed. Not really my idea of HA. When I told them that and what can be done they didn't believe me.
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