15 channel arduino 2560 with wifi to emoncms

We new users are apparently only permitted one pic per post, so here’s the promised second picture.

[Any moderators out there want to up my status please?]

You’re promoted.

Well thank-you! Is there a payrise associated with that? :wink:

That’s what the previous few posts have been about. The emonTx does use the 3.3 V and it is hard-coded (switched) via a preprocessor directive. It might be more accurate initially but also less stable than the internal reference.

Only if I get a back-hander. :innocent:

So my 4-point graph isn’t totally accurate then (now there’s a surprise!)

Got it. I’ve been focused on the TX shield. Now I see the special case in the emonlib.cpp code. My feeling is that the stability appears to be a pretty small issue compared to the problem of getting in the ballpark, which readVcc using the internal ~1.1V reference does not seem to do well. Thanks for walking me through this. My strong point is the firmware.

Here is a pic of my prototype “MegaMon”. It has been in service for several days now.

  • 15 input channels
  • integrated internet connection
  • onboard SD data logging (on internet shield)

Uses mostly commodity components:

  • Arduino Mega2560 (Sainsmart $12).
  • Standard arduino W5100 internet shield x/SD ($10 new on ebay)
  • TPlink wireless client ($19 Amazon)
  • 9vDC power supply brick
  • 9v AC voltage reference adapter

The three CT input boards are different versions of prototype circuits. They all work fine but have some differing characteristics, the best of which will be incorporated in the final design.

The two CTs with black and white wires are Magnelab SCT0750-000 CTs on the 200Amp mains. These are pricy but I had them already. I have a pair of YHDC SCT019 on order. They are $13 each and should work about the same.

The other CTs are YHDC013 30 and 50 amp versions. I paid about $6 each from China via Ebay. 2 weeks free shipping. Very well packaged. I’ve bought several batches from this seller and am well satisfied.

Next step is to design and get a prototype shield circuit board to put it all together. What I like about this solution is that most of the components are plug-and-play commodity items. The wifi connection is handled via TPlink browser based software. The internet board is standard. The processor is an inexpensive commodity.

Once I get an Eagle or other design for the shield, it will be pretty inexpensive to have a board made, and the components shouldn’t add up to much more than about $30. Will post again when I have a shield prototype.

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