Can any of the OEM hardware be used to monitor quick voltage spikes in the line? My initial use case is focused on my mom’s house where she’s having trouble with light bulbs blowing out frequently. My guess is that there’s a motor in one of the appliances that is creating a voltage spike on the line. I’d like to plug in the monitor and have it record high voltage event timing over the course of 24-48 hours and then be able to track down the timing to events (i.e. started the dishwasher, etc). In reading the startup guide, I understand that the standard hardware uses an average of the voltage over 200ms, but I’d prefer to have it sit and monitor the voltage without any time averaging and only record events that are over a preset threshold. Is this possible?
It should be, but you’ll need to wait a little while for the “continuous monitoring” library to finish testing, then you’ll need to heavily customise the example emonTx sketch to record (and send somewhere?) the over-voltage events.
The standard emonLib library routine averages over a defined period, then takes a break while it sends the data. You could miss a spike while that happens.
The new ‘CM’ library (developed from Robin Emley’s energy diverter) does as it says - it monitors continuously and reports the average over a defined reporting period. The minimum reporting period is 0.1 s, so if your spike is big enough to take the average up appreciably, you’ll detect it. Then, because the emonTx is working quite hard, I’d suggest you need to simply send the voltage reported somewhere, and log it there. This could be as simple as a serial connection to a laptop, or it could be radio to emoncms or similar.
One thing you will want to do is power your emonTx (because that, or an emonTx Shield running on an Arduino, is what you want) independently, from a well-regulated 5 V d.c supply or whatever the Arduino needs, and use a 240 V a.c. adapter so that it’s got plenty of headroom to record the spikes accurately. The US 120 V adapter will only measure a ‘standard’ over-voltage. I can’t remember offhand exactly how high it goes, but if spikes are blowing lamps, they will probably be quite big ones.
A friend of mine in rural Scotland had similar problems from a neighbour’s farm putting spikes on the supply, I fitted a transient surge suppressor for him.
Alternatively, have you considered hiring a suitable instrument? I’ve no idea what that might cost you where you are, but you would be sure to get meaningful measurements that should be good ammunition to use against your electricity supplier, whereas a DIY solution would carry less credibility.
Buying something like a “Mooshimeter” (don’t be put off by the silly name) may prove cheaper than hiring something more sophisticated, after all no matter how accurate your own readings are, the energy company will probably only treat them as indicative at best.
It’s basically a headless dual channel data-logging multi-meter based on 2x 24bit ADC’s, It has a microSD card slot for upto a 32Gb card which will apparently store over a week of dual 8kHz sampling.
The dual channels are to track voltage and current simultaneously to provide real power and pf measurements, Although primarily intended to measure current by connecting in series, it also works just as well with a current output “current clamp” (rather than voltage). I use one with a Fluke i400 AC Current Clamp.
Rather than an inbuilt display it is bluetooth and you use your phone to view either a Dual DMM type screen or alternatively a dual trace scope like screen.
That would depend on the instrument used. US energy providers generally will investigate any reasonable complaint.
If he uses an instrument that has traceable calibration, they generally accept that as a reason for a “closer look.”
The only downside there is it’s a $120 tool that may get used only one time.
Agreed! but at less than one weeks hire of the preceding suggestion, I would rather own one of these for ever than something else for a week. and being a more “general purpose” tool it might get some other use.
My inclination would be to go for the Mooshimeter, rather than a home-brew Emon solution - unless of course Tim either has most of the Emon parts he needs, or plans to buy the Emon monitor and put it back to its original purpose when the investigation is complete.
The transient suppressor I mentioned above was from ABB’s OVR range. I presume these or similar are available in the USA.
Great feedback; I really appreciate the perspectives you’ve taken the time to express here. A few of my thoughts:
The Mooshimeter is a good thought; I wasn’t aware of the product being on the market. I’ll have to research a bit on what it offers, and specifically focusing on its ability to identify voltage spikes and record that information. Logging voltage over time is interesting to me, but I’m more focused on identifying the first time the line voltage goes above a given threshold and timestamping that event.
I have to admit, my interest in the OEM hardware isn’t just limited to diagnosing this single problem. Rather, I’d really like to fix the issue at my mom’s place and then take the hardware back to my place and use it as it was originally intended.
On the thought of involving the energy company, my guess is that it’s something inside the house, and not an event from outside the house. If it were an issue with the energy company, I would assume that her neighbors would be similarly affected, and I don’t believe they have been. Thus, I think there’s a bad motor or connection somewhere inside her house that’s causing an issue.
Robert, any idea on the timing of the “continuous monitoring” testing completion?
If there’s a flaky connection on the neutral line that feeds her house, the neighbors would be unaffected.
It took me quite awhile to recall, but your issue had a familiar ring to it. Eventually I remembered reading about a split-phase system becoming unbalanced when the neutral line feeding the load center gets flaky.
When that happens, the legs get unbalanced and the result can be something like 150 Volts on one leg and 90 Volts on the other leg.
I confirmed the bad neutral connection idea with a friend who is the Electrical Dept Superintendent for the city he lives in. He said bad neutral connections were not uncommon.
If the bulbs she’s losing are always in the same room, then you could have a bad neutral connection between the load center (breaker panel) and the room. If the blown bulbs are in various rooms, the bad neutral could be in the load center itself, or between the load center and the transformer. (power company fixes that connection)
My friend said “ask her if she has noticed the lights flickering. if they get brighter and dimmer.”
He said given the number of bad connections he’s found at the service entrance, that it’s likely to be the culprit.
I second Bill’s comment about the lost neutral. In the extreme case, you could have very nearly 240 V on the 120 V circuit. That’s unlikely, but not impossible: if you have just a single lamp on the one leg, and several largish loads on the other, the voltage will divide in the ratio of their resistances - something like 250 Ω to 5 or 10 Ω so 230 V across the lamp, and 10 V across the other loads.
Sorry, no. I’d hope it will be a matter of a few weeks, but it rather depends on what, if anything, is found. It’s a huge and complicated piece of code, so there’s plenty of scope for something having slipped through.
I might just wait for a few weeks to see how the testing goes. Depending on what the module does, my ideal end state would be just to write a sketch that continuously monitors voltage, and then stores the time/date and voltage when the reading exceeds a given threshold. I could also just have it either write out to serial with a computer monitor, or I could have it display the time/date combination on a two line lcd screen. My plan is to initially hook up the monitor and then start turning on appliances and lights one by one to see if any of them can be traced back to a voltage spike. If that doesn’t reveal anything, I’d just leave it hooked up for a few days to see if the voltage remains constant.
I’ll be watching for the release of the continuous monitoring code.