1-Wire Problem

[RSin]

I've just come to add the 1-wire temp sensors. I'm using 3 wires so they are powered. I have GND and Data twisted pair (blue, blue/white) and VDD on orange in CAT6a shielded cable. If I add the sensor directly onto the 1-Wire Extension (200mm of cable) it works fine. If I then put the same sensor at the first 'real' location, perhaps 8m away, it can't be found in a search. I have used a tester with fly-lead and the cable seems fine.

Any Ideas?

as you can see I've followed the gospel of twisted shielded daisy chained. Any other known no-no's?

[RSinn]

Just to update the first sensor 8m away will not work directly but if I leave the sensor in the cabinet on the 200mm of cable and then daisy chain off that the 8m sensor springs into life...very odd, but it works!

[Duncan]

very short 1-wire buses can cause a very large signal reflectance which isnt a problem usually seen with longer cables

unused cores and the shield of the rj45 cable should be unconnected at both ends, not connected to earth

[AndyB]

The VDD on orange is a little risky with 1-wire.

Orange is usually reserved for 24V, 1-wire is 5V, so loxone recommends green/white for +5v, blue for data and blue/white for 1-wire GND.

suggested wiring: https://www.loxone.com/enen/kb/wiring-basics/

[Duncan]

Given that loxone recommend wiring 1-wires buses in the most unreliable of topologies possible i would thoroughly ignore what they have to say about wiring.....

[AndyB]

Was just pointing out that if you mixed cable colours on an install then could be confusing is someone else ever has to maintain the system. Wasn’t suggesting Loxones idea was right or the best just highlighting a possible option.

I personally wouldn’t use orange (or any other colour) for both 24v and 5v if both are wired in the system, unless there was some other obvious distinguishing feature.

[David Wallis]

On Thursday, December 20, 2018 at 11:54:06 AM UTC, Duncan wrote:

very short 1-wire buses can cause a very large signal reflectance which isnt a problem usually seen with longer cables

unused cores and the shield of the rj45 cable should be unconnected at both ends, not connected to earth

I would disagree with this personally, I would try groundin all unused cables - but only at one end, IE the panel. Or at least this is what I have to do on my alarm cables to prevent interference from the HF arc on my Tig welders. (and only where you have issues, otherwise I would do as duncan advises)

The colours used makese absolutley no difference - its the about what goes over the same and seperate pairs that matters.

Interested in how you get on with this as I am going to have a large 1 wire network in our house..  - Side note, why is there do easy way to add a device from the search / discovery?

[Duncan]

see

http://dutta.csc.ncsu.edu/csc453_spring16/wrap/1-Wire-Design%20Guide%20v1.0.pdf

page 58 regarding grounding of unused cores and screens increases the capacitance of the cable, and therefore slews the signal pulses

ive got a single 1-wire going around a 500m2 house, around 40 temp sensors over 2 floors, every room + 4 ufh manifolds and a single rfid reader and its 100% reliable

[David Wallis]

what would they know! I stand corrected, but still advise trying stuff for yourself. especially if the wiring is in already :) will have a good read of that cheers Duncan.

David

---

From: loxone-...@googlegroups.com <loxone-...@googlegroups.com> on behalf of Duncan <joanne...@gmail.com>
Sent: Friday, December 21, 2018 4:05:33 PM
To: Loxone English
Subject: Re: 1-Wire Problem

 

see

http://dutta.csc.ncsu.edu/csc453_spring16/wrap/1-Wire-Design%20Guide%20v1.0.pdf

page 58 regarding grounding of unused cores and screens increases the capacitance of the cable, and therefore slews the signal pulses

On Friday, 21 December 2018 08:18:22 UTC, David Wallis wrote:

On Thursday, December 20, 2018 at 11:54:06 AM UTC, Duncan wrote:

very short 1-wire buses can cause a very large signal reflectance which isnt a problem usually seen with longer cables

unused cores and the shield of the rj45 cable should be unconnected at both ends, not connected to earth

I would disagree with this personally, I would try groundin all unused cables - but only at one end, IE the panel. Or at least this is what I have to do on my alarm cables to prevent interference from the HF arc on my Tig welders. (and only where you have issues, otherwise I would do as duncan advises)

The colours used makese absolutley no difference - its the about what goes over the same and seperate pairs that matters.

Interested in how you get on with this as I am going to have a large 1 wire network in our house..  - Side note, why is there do easy way to add a device from the search / discovery?

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[RSinn]

Cheers for all the information. I think I've done what is suggested, no grounding.

Strangely it still seems a bit flakey. Maybe it will settle. It was working for 12 hours or so then failed. The reason behind me getting this working is for frost protection. The problem is that it fails and the input retains its last measured value, one was stuck on 15degC and another on 19degC. I could see the temp dropping to 0degC but the system still thinks it's 15degC. Is there any way to get it to pick up on faults and default to 0degC? That way the boiler would kick in. I'd prefer to waste energy than burst pipes!

[Duncan]

the main thing is to get your system reliable, but in the mean time you could put some logic around the sensor

in loxone config, there is a tick box for display error output when you select a sensor on a page - i dont know whether this will help at all in the logic or just the interface

a combination of several sensors and outside sensor or weather information could be combined to create a fallback

[RSinn]

Yes that seems like a good idea with the weather data. It'd need to be 2 independent systems. Problem with 1-wire at least for me at the moment is losing one sensor seems to kill those in the chain after it. It would be good to have something similar to a dmx splitter so I could have the outside temp and a few others on one leg and the the rest of the house on another. That way you don't lose everything if one goes.

I think it may actually be down to the connections at each sensor. I have some push fittings solder to a.little bit of board that the sensor is soldered to. The idea was I can bang out all the soldering at a desk and then push fit them easily in the back of light switches rather messing around with soldering at the back box. I might discard the connector and hard solder to see if the reliability improves

[RSinn]

[Duncan]

mechanical connectors are a real problem for 1-wire networks, along with side stubs off the main loop

i used jst sm 3 pin prewired connector pairs from aliexpress soldered on to the 1-wire sensor at 1 end and soldered to the cat5 at the other, then you can replace the sensors easily if required - use heatshrink to insulate and secure the soldered connections

https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20181223010521&SearchText=jst+sm+3

[Andrew B]

I'm using mostly RJ45+cat6 for my 1-wire network, and it seems to work reasonably well.  A much worse problem in my setup is that I didn't consider that running the 1-wire cat6 near low voltage PWM DC or mains voltage AC would generate EM noise on the network.  It still works, but the error counts go way up when the lights or some appliances are running.  Some of my sensors only yield new readings about 1 out of 5-10 attempts.  Fortunately this is still fast enough for my needs.  The worst one (also happens to be one of the least important, fortunately) occasionally doesn't report for hours when certain lights are on.

[David Wallis]

much as I hate the idea of pointlessly using cat7, I may just for the 1 wire network!

I need to work out a route around the house now... can the extension be in the middle of the Network or does it need to be at the end... assuming a perfect bus network with no spurs etc

[Duncan]

it needs to be at the end

[RSinn]

David. I found some cat6a that is pseudo cat7. It has a figure-8 wrap of foil so each pair is foil wrapped and then the whole bunch. Seemed to give cat7 and a bit of a reduced cost. It's Draka (Prysmian) so top notch.

https://www.canford.co.uk/DRAKA-CAT6A-DATA-CABLE-Solid-conductor-Low-fire-hazard

[David Wallis]

Nice find, will take a look at getting some of that

[RSinn]

Yeah also makes grounding easy at the cabinet because of the drain wire. Don't have to mess about with clips etc. (See other thread). Just order enough to qualify for free shipping. Think it's £100 ex.VAT. they've got a really nice dmx cable but it's expensive.

[DavidL]

I'm sure you'll be using this cable soldered, or using wire connectors. But just in case, bear in mind that cable probably won't fit in standard RJ45 connectors!

[RSin]

I'm coming back to this issue. I had a couple of sensors working for 2 days, then 2  of 3 failed, the working one is in the cabinet and only 100mm long cable but has been fine for months.

cale seems ok as i've tested with a Megger

decided i should abandon the push fits on Duncan's advice and soldered everything. still nothing.

so i think it is 1 of 2 things: bad batch of sensors (aliexpress, loxforum suggests there are fakes about) or the extension.

Can you share a link to where you get the 1-wire sensors please?

(not the ones already on pcb, but the raw sensors)

fyi these are the ones i have. seem to be good based on reviews

https://www.aliexpress.com/item/Free-Shipping-10pcs-DALLAS-DS18B20-18B20-18S20-TO-92-IC-CHIP-Thermometer-Temperature-Sensor/32523899337.html?spm=a2g0s.9042311.0.0.27424c4dfg9JcW

[Deac99]

I've bought about 50 of them (10 per order) from a guy on ebay (a few years ago who I just looked up and he does not have any anymore) and never had a significant problem with any of them.  I would assume they all come from the same supplier in China so I have a hard time believing the ones you got from Ali  were sub standard.  BTW - the sensors I got are the ones in the stainless case that are all waterproof and prepped with the wires - not the transistor looking ones - from Ali they were similar to these: https://www.aliexpress.com/item/Free-shipping-50pcs-lot-NTC-temperature-sensor-probe-4-30-mm-10K-1-3950-3435-wire/32270880126.html?spm=2114.search0104.3.123.66ac281c75p0aE&ws_ab_test=searchweb0_0,searchweb201602_7_10065_10130_10068_10547_319_317_10548_10696_453_10084_454_10083_10618_10139_10307_10821_537_10302_536_10902_10059_10884_10887_321_322_10103,searchweb201603_70,ppcSwitch_0&algo_expid=310d2bf2-fe1d-4f4c-a294-cc06541b2af2-18&algo_pvid=310d2bf2-fe1d-4f4c-a294-cc06541b2af2

Have you tried connecting a "Bad" sensor directly to the 1-wire extension with no other sensors connected to rule out that it is a sensor problem?

I still get occasional failures (once every 8 weeks for about a minute) but I'm confident it is due to the bad topography that I have (it's all over the place) and the fact that I am using Wago connectors.  This summer I plan on changing to a linear topography and soldering connectors as recommended by Duncan.

I too am curious what other people buy for these.

[David Wallis]

I thought I was having 1 wire issues with loxone, looking at grafana - however.. 

I do see something slightly odd in that /node-lox-ws-api doesn't seem to be outputting the data reliably when it changes on some sensors.. 

see attached

David

[David Wallis]

forgot to attach the graph which shows the two traces at the bottom

[RSinn]

@Deac
I have some of those sensors too within floor screeds. Not connected them yet as I can't get the 1st sensor in the daisy chain working properly!
I did bench test both types of sensors before deploying and they seemed ok.
I've soldered in a second sensor in the same location and still nothing.
I have used a Megger to 'bell out' the cable and it's ok.
I may try grounding the cable at one end, perhaps soldering with the 1-wire GND?? As my cable has a drain wire I'm wondering if it's causing an issue. Worth ruling it out, right?
If it's not that then dodgy extension? Maybe not supplying enough power?
Like I said it works for a sensor 100mm away, just not 6m away. Very odd.

[David Wallis]

FWIW.. A megger might not be the best thing to use if the sensor is connected due to the voltage they put on during the test!

Fine for testing the cable in between though.. 

Does the mini server diagnostics show any errors on the 1 wire - I was seeing errors on polling cycles.. Which I resolved - but made no difference

[RSinn]

Yeah only used the Megger to test the cable!

Not seeing any diagnostic issues, but I may be looking in the wrong place! Have you got a screenshot?

[David Wallis]

Clicked on Miniserver diagnostics and then it shows the extensions.. you can hover over and it will tell you the number of errors since boot.. 

Mine occasionally flashed up errors on the can bus / loxone link.. removing my terminating resistor fixed this - Need to double check the value of the actual resistor I used, but on a short length its working currently so not as bothered given its a temporary install prior to the renovation!