Hello,
I'm looking at buying a unit here and would like to order the kit of the emontx V2 and assemble it myself. I'd like to have something as precise as possible and I've been trying to figure out if V2 is as precise as the emontxV3? I know V3 has the 4.5 kW input, but I would be monitoring sources with more power anyway (mostly heating, which in some rooms ends up being 5000W).
In the blog posts concerning the release of emontx V3, they mentioned that the current sensing parts remained the same but were changed to Surface Mount Parts, but I just want to make sure. From what I have read, it probably wouldn't be a good idea to attempt to assemble a V3 unit as I have never tried soldering surface mount parts, although I'm usually not bad at soldering through hole parts.
Thanks for your help!
Re: V2 Vs V3 Hardware
As far as I am aware, both versions of the emonTx have very similar performances. An advantage of the V2 version is that you can choose your own component values for each of the input sensors. With the V3, all but one of the burden resistors are scaled for whole house monitoring and pre-soldered. Those channels may be rather insensitive for your needs.
I have several blank V2 PCBs here plus various associated components which you could have for minimal cost. I bought them all through the shop so don't feel I'm cheating anyone out of another sale ;p
Send me a PM if you're interested.
Re: V2 Vs V3 Hardware
Also, the V3 does not need a separate 5 V power supply to operate (provided that you have no high-current add-ons) if you are monitoring the voltage. You don't need to assemble the basic V3 circuit board, it comes assembled apart from the radio module and battry housing. It's fairly easy to remove the on-board SMT burden resistors in the V3 and replace them with through-hole wire-ended resistors with the value of your choice if you find the conditions require that. And although I have not done rigorous tests to prove it, I have a feeling that the low-current performance of the V3 is somewhat better than the V2 on account of the precautions taken to minimise noise pickup from the digital circuitry. Otherwise, the performance should be the same when both have been calibrated.
Re: V2 Vs V3 Hardware
Hi guys,
Since I was looking for a project to assemble myself, I guess I should probably go with the V2 if the precision is not greatly affected. This would also make a good prototype for me to experiment with, as I am looking at making a complete home monitoring system. What would you guys roughly consider low current applications? Most of my panel is made up of 20-30 amps heater circuits, so I think I would be good to get a fairly precise reading on most of my consumption.
Another question I had was about sampling rate. From what I have read so far, sampling intervals is every 10 seconds. With the electronic thermostats, my heaters are "flashed" for a couple seconds every couple seconds depending on how far from target temperature the room is. I'm just wondering if the sample rate will have me miss heating "events", thereby affecting my precision.
One thing I'm not sure I've understood right is the way the programming sketches are handled in V2 VS V3... From what I have read, emontx V2 needs to have a firmware adapted to whatever reading you want to take, and V3 can interpret readings all at once, without needing to uploading a different firmware sketch. From what I understand, billing is solely based on real power measurements, so unless I'm just playing around with different measurements for fun I'll probably always be measuring real power?
As you can probably see, I'm lacking experience and knowledge on energy monitoring compared to most of you guys. However, I have to say I'm pretty impressed with this project, and most especially with the support offered by this community.
Louis
Re: V2 Vs V3 Hardware
If you want to assemble a kit from the basic components, V2 is the way to go. If you're looking to measure 30 A loads, then you're going to want to change the CT's burden resistor and that will give you a channel that reports 0 - 30 A with the best resolution.
"Another question I had was about sampling rate. From what I have read so far, sampling intervals is every 10 seconds. With the electronic thermostats, my heaters are "flashed" for a couple seconds every couple seconds depending on how far from target temperature the room is. I'm just wondering if the sample rate will have me miss heating "events", thereby affecting my precision."
That would be a major problem for the default sketches (which you've obviously been looking at), but fortunately we have an answer to that. There are in existence two families of "continuous monitoring" sketches that do exactly what it says - although they report at roughly the same frequency, they do monitor continuously and return the total energy / average power since the last report. So while you'd expect the sampling sketches to get it right when averaged over an extended time period, the continuous sketches get it right. Always. Those are the sketches on Github with 'continuous' in the name, or with a bit of digging you'll find MartinR's phase locked loop energy diverter that, when you ignore the diverter code, measures continuously and reports every few seconds just like the other sketches.
As far as the sketches go, there's no difference (apart from pin numbers and I/O allocation) between the V2 and V3, and sketches can be translated between the two in both directions very easily. The majority of V3 sketches have a V2 heritage. So I'm not quite sure what you're understanding there and where it came from. Are you comparing the later sketches that work more like an energy meter against the earlier ones (intended originally to be battery-powered) that work more like a wattmeter?