EmonTX: AC-AC Adapter: No voltage readings

Submitted by charliemic on Sat, 16/11/2013 - 10:35

All,

I'm trying to get an EmonTX to give real power readings, so have got an AC-AC adapter and using the C123Voltage sketch. It didn't seem to be working so I've uploaded the minMaxandRangeChecker sketch to see what's going on.

The AC-AC adapter is plugged in to a socket near my PC (NOT near the incoming electrical supply). I know this is supposed to be within 1m of the incoming supply, but how important is this? I assume this is just for accuracy, and it should still pick up a signal wherever you put it?

Readings from the minMaxandRangeChecker as follows;

513 514   1;   507 508   1;   509 510   1;   459 506 47
513 514   1;   507 508   1;   509 510   1;   497 515 18
513 514   1;   507 508   1;   510 511   1;   497 515 18
513 514   1;   507 508   1;   506 514   8;   497 515 18
513 514   1;   507 508   1;   510 510   0;   497 515 18

I don't know what these numbers mean (what are the units?), but this looks to me like nothing is happening as they are basically the same as the other inputs which have nothing on them.

I also notice that the AC-AC adapter appears to be stone cold, when I would have assumed it would get a least a bit warm.

I terms of hardware, the connections on the barrel to the EmonTX seem solid enough. The TX has been working find for CT only monitoring and temperature too.

Any thoughts? Do I have a broken AC-AC adapter?

Chris

Re: EmonTX: AC-AC Adapter: No voltage readings

Submitted by glyn.hudson on Sun, 17/11/2013 - 00:32.

Hi Chris

I'm not familiar with the Min and max sketch however it is usual for the ac adapter to get slightly warm when plugged in. Have you got access to a multimeter? Most meters will have an ac voltage reading setting. This will allow us to check for sure of the adapter is faulty. Being more than 1m away from the utility meter should not be a problem. Contact us direct if you believe you have got a faulty adapter.

Re: EmonTX: AC-AC Adapter: No voltage readings

Submitted by charliemic on Sun, 17/11/2013 - 09:07.

Hi there Glyn,

Thanks for getting back. I do have a multi meter but it only goes down to 200V ac, gives zero reading, and not picking anything up on the DC settings either. Sounds like it is faulty? I will email you directly.

Chris

Re: EmonTX: AC-AC Adapter: No voltage readings

Submitted by calypso_rae on Sun, 17/11/2013 - 19:52.

Readings from the minMaxandRangeChecker as follows;

Hi Chris, those readings are the raw ADC sample values (Min Max and Range) for each of the the first four analogue inputs in turn. If you check the silk screen markings of the emonTx (or the schematic diagram on Solderpad) you will find that An0 corresponds to CT2, An1 is CT3, An2 is the voltage sensor, and An3 is CT1.

For each set of columns above, the mid-point is around the 500 mark which shows that your biassing networks are all fine. For An0, An 1 and An2, there is minimal AC signal. For An3 (CT1), there is a small signal with a range of around 18 ADC steps. With full range being 1024 steps, this signal is using 1.7% of full range.

With an 18R burden, this usually corresponds to a max signal size of around 100A. So that suggests to me that you are measuring a current of around 1.7A or 420W at CT1 (An3). If you are not measuring any current via CT1, then something looks to be wrong with that circuit.

The signal from your AC/AC adaptor (for the voltage sensor) should appear in the third set of columns. Apart from one spurious value, this circuit does not appear to be doing anything. When using the standard shop-supplied components, you should be seeing a range of just over 900 in this column (the right hand one of the three in bold). That's what was seen when a newly build emonTx was checked using this program yesterday at MadLab.

You could easily check whether the AC/AC adaptor is producing any signal by touching an LED with a series resistor (e.g. 1K) across its output connections. If the LED lights up, then your adaptor is probably OK.

Re: EmonTX: AC-AC Adapter: No voltage readings

Submitted by charliemic on Tue, 19/11/2013 - 22:16.

Thanks for that.

I've got a new ac adapter now which gives a Max value of around 900 as you said, so I think that confirms that the old adapter was faulty.

For the results i posted before there was nothing connected to the CT inputs! I did have a temp sensor connected to the corresponding port but I don't think this should make a difference?

Chris

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