How to: multiple ds18b20 wiring?

I want to connect multiple ds18b20 temperature sensor in a single bus. My question is not about how to wire those sensors to have they working or how to write the code... is about how to physically wire and solder those sensors in a single cable. I will not use long cables, ever less than 4 or 5 meters, including about 10 sensors each line, not regularly distributed along this distance. Probably i will use normal power for them (not parasitic mode).

I readed in different places in this forum that the people connecting multiple sensor to a single bus use cat5 or cat6 cable... so, following their experience, i will do it in that way. But, how to connect the sensor? I know, i know, removing the plastic to three wires and soldering the legs of the sensor. :stuck_out_tongue:

How do you wire them? Do you use a special connector to the cable to derive three of the wires to solder there the sensor? Do you solder the sensor directly to the cable?

In my project, some of the buses will be outdoor, so, i have on mind to protect inside a plastic tube (of something like this), with hole where the sensors will go outside to be exposed to the environment, but all the other connections will be inside the cable. To use somekind of tiny connector between the main cable and the sensor could be a nice idea just in case to replace a possible defective sensor in the future. The devide will be in the middle of anywhere, so to solder in the field is not an option, and to replace all the bus is a very remote option (require to have a copy of the cable and all the sensor already ready). I think that to have the sensor with an short cable, ready to connect to the main cable is the perfect solution. So, in case of fault of one of the sensor, to unplug the broked one and the connection of the new one is enough, remaining the main cable and all the other devides in place.

Now that you have the big picture of what i hace of mind, do you have ideas, proposals or comments about how could i do that? They will be wellcome. Thanks so much!

Ive not read the whole text but, when ever u use only one interface you wire them in a row or tree with maximum 1 meter distance. Do not use star distribution!!!!

Read here:
ftp://ftp.elin.ru/pdf/1-Wire/DGuide1.pdf

Use thin wires. For example CAT5e UTP means without any shield or net or something.

Thanks so much k4ktus for the tips!

If you want to avoid soldering you can use a 3-wire ribbon cable and 3-pin IDC (Insulation Displacement) connectors. Just crimp them on wherever you need a sensor.

madepablo:
I will not use long cables, ever less than 4 or 5 meters, including about 10 sensors each line, not regularly distributed along this distance.

I readed in different places in this forum that the people connecting multiple sensor to a single bus use cat5 or cat6 cable...

In my project, some of the buses will be outdoor, so, i have on mind to protect inside a plastic tube (of something like this), with hole where the sensors will go outside to be exposed to the environment, but all the other connections will be inside the cable. To use somekind of tiny connector between the main cable and the sensor could be a nice idea just in case to replace a possible defective sensor in the future.

I think you have answered your own question. The distances you envisage are not great, I don't think there are any specific wiring requirements in the data sheet, and you can do more or less what you like.

I think the reason why people use CAT5 is because it is cheap for the quality, and an obvious choice, particularly if you have a terminal tool. All my sensors are waterproof and come with 5m cable. I had trouble with an extension and I believe this was because I used cheap thin cable. I thought the cable needs to be shielded. This is not true.

In my case, the bus, such as it is, is on the shield and all the sensors are brought back to that. You could use the same waterproof sensors and cut up the cables to make a daisy chain of short branches terminating in 2.5mm stereo sockets, with the sensors terminating in matching plugs. The branches and the connectors are then all easily protected with heat shrink tubing. The sensors are cheap on eBay with varying lengths of cable, and can be bought sans plug.

Thanks!!

THe idea of the stereo jack sounds interesting... may be the 2.5mm one could be better because it is smaller.... Uhmm, interesting. Thanks for the tip!

Please read the one wire guide. Stereo jacks are not that good. They have a very high capacitance and mostly a high contact resitance. Both things are bad to a one wire network.

upps! I still didnĀ“t read that information... i will do it carefully. Thanks for point to me that information!

I would read it with some serious skepticism until some reliable verification came through.
I fail to see where the high capacitance comes from and await some detailed explanation with interest, particularly in view of the amount of cable in the system compared with the weight of the terminals.

To dismiss them for high resistance is suss for much the same reason but you might find some gold-flashed ones around if anybody else saw this as a problem, and the ease of weatherproofing and re-use is likely to more than make up for any deficiency in this arena.

I have a store-bought one-wire network kit spreading over thirty metres with six probes, branches, extensions etc. that can be cobbled up how you like, all done with plain-vanilla 2.5mm stereo jacks and it works just fine. I assume this system uses shielded audio cable, but most of my sensors for arduino use plain 3-conductor cable.

Although I run my 7 ds18b20s in the parasitic mode, I do find that getting a response is easy and the readings/sensors are very stable. I am using my inside telephone wiring, along with 2 different runs of cat5 cables, all tied in parallel. If you are sure that your wiring and sensors are correct, there are two items that you need to watch. The resistor value (up or down) you may need to play with and, the Arduino gui. If you have made a physical change and you are using the software's Serial Monitor to view any change, make sure that you close the Serial Monitor and re-open it, or just restart the Arduino software all together. I had made a physical change and then kept receiving all 32 F or 185 F on all sensors. It was frustrating until I did either one of the above, I just don't remember which one.

sp_mike:
If you have made a physical change and you are using the software's Serial Monitor to view any change, make sure that you close the Serial Monitor and re-open it, or just restart the Arduino software all together. I had made a physical change and then kept receiving all 32 F or 185 F on all sensors. It was frustrating until I did either one of the above, I just don't remember which one.

I believe this latter sounds like you are sailing a bit too close to the wind as far as power is concerned. If you are using the USB cable for power, I'm sure this would be fixed by using a 9v wall wart instead.

Hoi,

have also a look at this thread:
http://forum.arduino.cc/index.php?topic=188906.msg1398480#msg1398480

There are many informations about how to wire and what bus-topology to choose for different issues.