Measuring temperatures…

Absolute beginner - here. I’m going to try to see if I can monitor flow and external temperatures for my system. For historical and space reasons all of my meters, my heat battery and the heat pump controllers are all tucked away under my stairs. How long a cable can i run for the DS18B20 temperature sensors? Do I specify the length of each one at the checkout or is there an extender that I need to add to run the cable all the way to the outside of my house (probably 10 m or so once I’ve wiggled around under the carpet and along the skirting boards.


Welcome, Andrea, to the OEM forum.

Much has been written here about the DS18B20 sensor, so you have a lot of reading to do.

First, a very full explanation of the One-wire System -:

Wiring DS18B20 sensors: DS18B20 reliability considerations

Much about clone sensors & multi-drop: Ds18b20 and emonTX3CM firmware - post 78 in particular.

Temperature sensors don’t work:

There are two articles in the ‘Learn’ section here: Learn→Electricity Monitoring→Temperature

Maxim App Note re wiring: Guidelines for Reliable Long Line 1-Wire | Maxim Integrated

1-Wire DS18B20 direct to RPi: Enable 1-Wire Interface on the Raspberry Pi - Raspberry Pi Spy

And we have a sketch for an emonTx (or Arduino) to read the sensor serial numbers - knowing those can be very useful.

I think your best approach will be to read as much of that as you can absorb, then come back with questions.

“The Shop” sensors come with a fixed length of cable - if you have more than a few sensors and they are all some distance away, you will be much better arranging your wiring as a proper “bus” or daisy-chain, rather than bringing all cables back separately to a central point.

Don’t worry about that, we all were, once. If you’re prepared to ask questions and learn, and follow up our suggestions, most people here will stay with you and provide all the support that’s practical. Except for the 2 owners (Glyn & Trystan) and Gwil, we’re all volunteers. The one thing we don’t do is 1 to 1 phone calls (or whatever) - it’s all on the forum.

Do you already have any OEM kit or doing it all right now?

If you get one of these emonPi / emonTx RJ45 to Terminal Block Breakout for DS18B20 - Shop | OpenEnergyMonitor you can connect all the sensors to it and then run a normal network cable to wherever the EmonPi/EmonTX is.

Are you sure about that reference? I think that particular post was about pt1000s (my bad for going off topic at the time).

I think it shouldn’t have the “/6” on the end. Thanks.
(I’ve changed my “fount of all knowledge” text file. :smiley: )