Emontx V3 showing pulse reading


I've just recently bought an emontx v3 and raspberry pi base. I have manage to get it to read my mains electric and have it powered by 5V USB and the 9V AC-AC adapter. The only thing that confuses me is that on my nodes it is reading a pulse value even though I have no pulse counter and even stranger is that the reading changes. I have tried powercycling the emontx and the raspberry pi but the reading is still there. Any ideas?

I also would like to connect some temperature sensors and have 5x DS18B20 can someone advise which pins I should use If I want to attach RJ45 connectors to them as the digging I have done has given me conflicting information. From what I can find its 

Pin2 - +5V (RED)

Pin4 - Data (Yellow/White)

Pin5 - GND  (Black) 



Robert Wall's picture

Re: Emontx V3 showing pulse reading

The pulse input is clearly picking up noise from somewhere. Have you been handling the emonTx? touching the connections at the back of the RJ45 socket is enough to register pulses.

The Waterproof DS18B20 from the shop without the RJ45 connector is wired as you say, if yours came from there you should be correct.

claytonie's picture

Re: Emontx V3 showing pulse reading

I gave up on the RJ45 connection as I couldn't seem to get a reading. I wired a piece of CAT5 into the screw in terminals and put and RJ45 with coupler on the other end of the cable and now I am successfully reading temperatures from 2 temperature sensors.

Even with just a CAT5 patch lead plugged into RJ45 port with nothing else plugged into the other side the pulse reading starts to increment as soon as I unplug the patch lead it stops. Could this be a fault with the board? 

dBC's picture

Re: Emontx V3 showing pulse reading

I might have missed a pull-up or pull-down in the schematic somewhere, but it looks like that input is just left floating in which case your cat5 cable might easily be enough to get it flipping.  Floating inputs can increase power consumption quite a bit too.  You could try enabling the internal pull-up to see if that prevents the counts.  Change:

pinMode(pulse_count_pin, INPUT); 


pinMode(pulse_count_pin, INPUT_PULLUP); 



Robert Wall's picture

Re: Emontx V3 showing pulse reading

I think you could be right there - I can't see a pull-up either. I'll flag it to Glyn.

That seems to work for me - it's no longer susceptible to a finger on the back of the connector.

glyn.hudson's picture

Re: Emontx V3 showing pulse reading

Thanks for noticing this. The issue only effects the pulse count when no pulse sensor is detected. However I've added to the default emonTx code to turn on internal pull-up on IRQ pin by default. I've tested and this fixes the issue and does not effect pulse detection when a sensor is detected. 


Westerner's picture

Re: Emontx V3 showing pulse reading

Glyn, will running the EmonPi update in Emoncms fix this issue in the EmonPi as well?

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