Archived Forum

Is JP2 closed ? http://wiki.openenergymonitor.org/index.php?title=EmonTx_V3#Power_Supply_Options

"9V AC-AC power adapter - with jumper JP2 closed (If jumper 2 is left open then the AC-AC adapter will be used for power sampling but not to power the emonTx V3 - see Powering via AC below) "

Paul

Is the link JP2 present? Did you power the emonTx without the programmer connected? What does the on-board LED do when you power up?

"I also checked the voltage across the soldered pins of the AC plug on the bottom of the board with the plug inserted and that read 11.9V which I think is higher than it would be if the board was getting power."

Not true. The amount of current drawn by the emonTx is so small that you would be unlikely to be able to measure any difference between the emonTx being there or not - it is less than normal fluctuations of the mains voltage. The drop according to my simulation is about 500 mV on the peak value of the positive half-cycle under maximum current loading, so the effect on the rms value will normally be significantly less than this.

You should see around 12 V dc on C1 (the 47µF close by the socket) and 3.3 V on the screw connector (both the 3.3 V and the 5 V terminals and on JP2.

There is no jumper on on this card or at least what I consider a jumper that you can move from a closed to open position.

There are 2 solder filled holes on the left side of the card that I guess one could bridge across.

The emonTx V3 I received a few months ago was not like this and worked out of the box with an AC-AC adapter.

Why would the shop send a unit not setup for the AC-AC adapter when you order it with one?

I spent the better part of the day trying to figure out what was wrong with this unit.

Thanks for the info, though I'll try soldering those 2 holes together.

Can you post a pic? it sounds like a modification or omission, I can't recall reading about a change to JP2 so the guys at the shop may be interested to see also.

Paul

If the two solder-filled holes are adjacent to the printed "JP2 AC-DC Power Supply  [new line]  Enable - 20mA MAX" then there should indeed be a 2-pin header with a removable link fitted there. If there is not, I'm pretty sure it is a manufacturing fault and in that case, can you confirm that and I'll raise the matter with Glyn & Trystan - or you can do that directly if you wish by email to sales@openenergymonitor.zendesk.com

The easiest way to get your board working is to solder tack a short length of tinned copper wire across the two holes.

Yep, but it will be a day or so as the unit is at my son's place and I won't be back there for awhile.

There definitely is not a normal jumper installed --- just 2 solder filled holes right next to the end of the battery holder.

I was not aware that the programmer could power the unit, so after I got it calibrated with an updated sketch, I didn't notice that it quit sending updates after I removed the programmer and moved the Base station to it's normal location.

Spent the next few hours trying to figure out what the problem was with the antenna / locations that I could not get updates.

Wasn't until I went back to try and upload a new sketch, that I noticed it started sending updates again as soon as I attached the programmer --- live and learn.

Wallace

All items in the emonTx range - emonTx V2 & V3 and emonGLCD - can be powered by the programmer. The NanodeRF can be as well.

I attached a photo of the emonTxV3 board showing the missing jumper headers.

I have now soldered a wire link across the holes and it works OK.

The measured operating voltage using the Shops UK plug adapter is 11.9V , which seems kind of high for a transformer speced at 9.6v --- will this cause any problems?

We have fairly high Mains voltage at this location --- frequently in the 248 to 258V AC range.

Wallace

That voltage sounds fine for an unloaded 9vac wall wart, the emontx v3 doesn't draw enough to effect the voltage which is necessary for the value to be relevant and there should be plenty of range on the input to cope with your expected highs.

Paul

There is definitely a manufacturing/assembly fault there. I've already emailed Glyn & Trystan and I expect they'll check the stock. Hopefully, yours is the one that got away.

The voltage is high because the adapter is essentially unloaded, and the voltage is specified at full load. The regulation of small transformers is often rather worse than the 20% that this one is. The input was designed to use that adapter over the full UK voltage range (to 253 V), I rather doubt that your mains is actually as high as 258 V unless someone on your substation has misguidedly installed a "power factor correction" unit, which will of course tend to elevate the voltage.

Oh dear, very sorry about this. Please email support@openenergymonitor.zendesk.com and we'll sort out a replacement and check our stock. 

No, I don't need a replacement --- this one is working fine now.

What really gave me a problem was that I didn't realize the programmer could power it, so after I had it calibrated for my CT's I was sure the problem was with the Raspberry Base / antenna location and not the fact that the emonnTx  no longer had power.

Thanks

Wallace