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Adding multiple DS18B20 sensors to emonTX3

Tags: #<Tag:0x00007fa34c2ec628> #<Tag:0x00007fa34c2f7ed8>

Hello,
I would like to add three DS18B20 sensors to my emonTX3 (purchased 1Jul17) using the RJ45 connection and I have a couple of questions:

  1. Is there a schematic that shows how to connect these (I don’t have the OEM terminal block) to a single RJ45 plug? The emonTX3 is powered by AC/AC and 5 volt USB.

  2. Will these three DS18B20 sensors be recognized by the emonTX3 software or will it have to be reflashed with an update? I think I will need to get the serial numbers at some point. In my emonhub.conf I see there is the section:

[[8]]
nodename = emontx3
[[[rx]]]
names = power1, power2, power3, power4, vrms, temp1, temp2, temp3, temp4, temp5, temp6, pulse
datacodes = h,h,h,h,h,h,h,h,h,h,h,L
scales = 2.1376,2.1376,1,1,0.0110144,0.1,0.1, 0.1,0.1,0.1,0.1,1
units =W,W,W,W,V,C,C,C,C,C,C,p

I am using my own RPI with RFM69Pi_433 and the latest OEM updates.

Thanks and please let me know if you need more information.
Bob

Yes, in the 'Learn" section, Learn→Electricity Monitoring→Temperature→DS18B20 temperature sensing→Temperature Sensing using DS18B20 Digital Sensors.
It’s a 1-wire bus so all 3 devices will be connected in parallel with the RJ45 plug (or the screw terminals) as the “star” point. The RJ45 connections are in the WIki - you’ve seen that: https://wiki.openenergymonitor.org/index.php/EmonTx_V3.4#RJ45_Connection

[Note that you’re asking for trouble if, with 3 temperature sensors, you go back to only the a.c. adapter power.]

Yes, they will be recognised at power-up or restart (and only then). No, you won’t need to update. And you shouldn’t need to get the serial numbers, but if one sensor goes AWOL, they will rearrange themselves if the addresses are not hard-coded into the sketch or into EEPROM (your sketch may not have the facility to store the addresses in EEPROM). The values should pop up in “temp1”, “temp2” & “temp3”. The order is somewhat mystical (unless you plug the numbers in manually) and is explained in Part 2 of that ‘Learn’ article.

Much appreciated for the info and pointers, Robert. I plan to leave the 5 volt USB supply in place (as well as the AC/AC) as it seems to have solved my emonTX3 dropout problem discussed earlier. Thanks again.
Bob

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