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This is ridiculously brilliant, more I want more, can you show me the insides and how can I ge hold of one of these ?

Wow, that looks amazing. Can we see inside? What hardware design have you used? Great work, very tidy implementation 

+1 for the coolness and +1 for having a look at the modifications, if that is something you guys are planning on sharing.

I could use a couple of these (even 10 or so) if they come with a din rail mount case (so far here in Italy that has been the major objection to people potentially interested in the project: no din rail .. no party because it would require a separate custom box instead of some space in an already existing and available one)

Here are some pictures of the inside:

The hardware is more or less based on this schematic:
http://solderpad.com/openenergymon/emontx/
 

As you can see we've integrated the transformer into the design. More design modifications are:
• Integrated usb connector and usb <-> serial connector
• DC/DC converter to provide the logic supply voltage
• Dipswitches to select the node ID
• As much SMT components as possible
The only downside of our current design is that the transformer is too small to work properly. Because of the small size of the transformer it uses a very small wire size to be able to make enough windings around the core. Thus saturating the transformer very quickly, even with small loads. This results in a distorted sinus waveform making the power factor slightly inaccurate.
We have already tested some larger transformers which work perfect without saturating, but unfortunately these are quite a bit bigger. The casing has to increase to a 40mm width in stead of 22.5mm to fit these transformers.

I notice you have the CE mark on your unit? What certification process have you put the unit through? Would you be able to share your experience? This is something we are looking to achieve with the emonTx V3 in the near future.

It's not officially CE certified yet, but it complies with the low voltage directive and we've also done a quick EMC scan(we can do pre-compliance EMC tests here :) ) which it easily passed. 

It's good to hear that a standard ATmega328 + RFM12B passes pre-compliance EMC. If you make any discoveries or have experiences please share. We will be doing EMC testing early next year

One of our RPis went corrupt after a power outage so I installed OEMGateway and pointed it to our dataserver to see how it works. All nodes started to send data again except for 2 nodes, node id 30 and 31. Could it be that the OEMgateway doesn't work with nodes from id 30 and up? 

I think it's a case of the JeeLib protocol supports nodes 1-30 only: http://openenergymonitor.org/emon/buildingblocks/rfm12b2

(It appears that the original JeeLabs documentation is no longer available. Martin Harizanov has reproduced an outline of the packet structure here.)

We´re currently working on the next revision of our energy node. We have chosen to use a resistive voltage divider to measure the voltage instead of the the transformer + voltage divider. This results in a clean voltage measurement, without the distortion caused by the transformer. To do so we've used 2(so one can fail) 1M5 resistors in series, both in the line and neutral. This reduces the current to a safe level.

We're still looking to further improve our nodes, what would you guys like to see added in our (industrial version) energy nodes? 

Sounds interesting, if you conduct any accuracy tests between the two methods please share. It would be interested to see how much difference this makes. Obviously isolation would be lost with the resistive technique. 

Did some testing today:

Phase angle between the 230v input and the measuring resistor, no parallel capacitor.

Blue is the 230V input, yellow is the voltage across the measuring resistor

Almost no phase rotation, but some nasty spikes on the measured resistor

Phase angle between the 230v input and the measuring resistor, 470pF parallel capacitor

Slightly increased phase angle, spikes seem to be gone.

Same tests with 1nF and 10nF, no benefit over the 470pF capacitor:

Buenas a todos.

Disculpad que os pregunte en español, pero mi ingles es demasialdo malo....

Un proyecto muy interesante. te felicito por el trabajo. Solo me surge una duda (desde mi desconocimiento de electrónica). Si en lugar de utilizar un transformador de 0,35vA se utiliza uno de 6vA, ¿los resultados de medida serían más precisos?. Por otro lado... ¿sería posible utilizar ese transformador para alimentar un componente de la placa que necesita 9vdc?

Gracias.