OpenEnergyMonitor Community

Daisy chaining DS18B20 with emonTx

Evening all and happy Monday!

I need to connect 4x DS18B20 temp sensors to my emonTx. I have an RJ45 breakout board, to which I could wire all 4. But two of the temp sensors need to be a few meters away from the other two. My plan was to connect two sensors to two breakout boards, and daisy chain them with ethernet patch cables to my emonTx. I have gone ahead and done this, but when I look at the Inputs list I can see T1 and T2 (the two sensors on the first breakout board in the chain) look to be working. There is also a T3 with a (non-300) reading, but no sign of T4.

I was naively hoping T4 would magically appear, so I am wondering what changes I need to make to cause T4 to show up as my 4th temp sensor?

Thank you!

There is a limit of 3 sensors in the emonTx code - simply because I did not have four to test it with.

You can change the number to 4 if you want to try it and add the 4th in all the places necessary, if you’re using emonHub you’ll need to change that as well.

Thanks Robert, I will have a go!

My fear, not being able to test, is that the 4th sensor will hold up the continuous monitoring bits, and corrupt the readings - or vice-versa. I can’t remember offhand which way round the problem would be. Reading that data from the sensors takes a long, long time.