Technical specification of EmonTX/ Emonbase units

Hi all, just a quick one. After a weekend of quite cold weather here in NI, particularly in the rural areas, we have had 3 units stopped recording to Out of the 6 setups we currently have recording, 3 have failed and I am wondering if the colder weather (0 degrees) might have caused this. Not only this, these units are installed in some pretty damp environments namely, farming outhouses, which can be pretty cold anyway. So I guess i’m asking - although maybe not ideal - if these environments may be detrimental to the units performance.


The only specification that I’m aware of can be found via “Resources”.

@glyn.hudson might be able to supply more details.

Hello @bez are both the EmonTx and EmonBase units in the outhouses or just the EmonTx transmitting to an EmonBase in a different location? There’s definitely a risk that any moisture could impact the performance of the units, neither are in sealed enclosures so that could be related.

Hi @TrystanLea. Yes, both units are situated within the same outbuilding, typically damp environments that contain the ambient outside moisture that creeps in (i.e., doors left open). But also milk tanks with varying temperature levels and also the heat/sweat of numerous cows whilst being milked. That’s not to say in the same room as the cows per-se, but rather adjacent rooms that allow for moisture build up over time. I think it would be safe to assume this is detrimental to performance.

With reference to my other post:

Proximity of EmonTX to EMonBASE units - Hardware - OpenEnergyMonitor Community

proximity of the EmonTX and EmonBASE to each other, could this have an impact also maybe?


Is this problem still remaining now that you’ve moved the two units apart?

If it is, I think I’d suspect the emonTx first, and condensation. There’s very little power dissipated inside the case - which isn’t sealed owing to the need to connect to the p.c.b. - so there’s a greater likelihood of condensation occurring.

Even if you don’t have the problem any more, from what you’ve written about the conditions, I’d suggest you still think about putting a little heat into the emonTx.

One thought would be to use the a.c. adapter to supply some heat. It’s grossly overrated as far as supplying the electronics is concerned, and a bit of load would actually improve the quality of the waveform, even though it will affect the calibration - because the calibration is based on the no-load voltage being 11.6 V (if you’re in the UK), whereas at full load, it will be 9 V. The adapter is rated at 10 W, so you could think about a resistor dissipating about a watt connected directly to the a.c. input socket. 120 Ω would give a fraction over 1 W, a 2 W or 3 W resistor would fine, I wouldn’t use a 1 W one - that would run quite hot. Or you could use 2 × 220 Ω 1 W in parallel, or 3 × 330 Ω 1 W in parallel.

That would affect the calibration by about 10%, which you’d need to correct, either in the sketch itself or in the emonBase. The voltage and power will be reported that much lower than they really are.

I’d have thought that there’s probably enough heat within an emonBase - provided that the enclosure is reasonably closed but allows a little ventilation - to keep condensation at bay.

Without checking each individual component, I cannot say definitively but it would seem unlikely that the problem is temperature alone - unless it goes some way below 0 °C.

[Edit] I’ve checked the processor and the radio, and the likeliest passive component - an electrolytic capacitor, and that’s the worst, being rated down to only -40 °C. So again, without checking each component, the temperature in a UK unheated building isn’t likely to be the immediate problem.