Mains voltage logger FAQ

I've got a Seaward mains disturbance recorder, it can count transients, and give a yes/no for any dropouts longer than 1/2 a cycle or 2 cycles, or any voltages outside of 240V +/-6% (pre-EU harmonisation)

It was used at a former employers to deflect blame from computers to energy suppliers!

When I lived in rural Devon, I was at the 'end of the line'. I was a long time ago because the picture on my TV screen got smaller and smaller as the voltage dropped. I rang SWEB who provided me with a voltage monitor. They then installed a new transformer when I was proved not to be making it up.

Yes we are out in the sticks, and I have a Extech Instruments DL150 Voltage/Current Datalogger which I use to monitor our supply.

Many 'smart plugs' which have power measurement also record mains voltage. They may be able to log that to their platform which can be seen in their app. They may not have a very high sampling rate (eg I wouldn't expect more than 1Hz, probably less), or range (very out of spec voltages like 1kV spikes may not be recorded)

If you have a logging platform (Home Assistant, Grafana, HomeKit, ...) it may be possible to log the data from such a plug externally.

Theo

Well sometimes LED lamps just flicker for no reaspn.

Of course you are using overhead wires, unless you are bang on a power station. The 275kV is all overhead

Not a hard job for a Pi PICO W.

You can sample the ADC at up to MegaHertz range

Interleaving that with network calls is a bit tougher,.

But then I like writing code. YMMV

Some UPS devices will connect to monitoring software and record events like this.

Mostly... It would be a trivial job to get an arduino or similar dev board to do what you need.

Something like the little hack I did for a real time power monitor:

You could take the circuit:

On 27/01/2025 01:45, John Rumm wrote: could be greatly simplified and co-opted to do just voltage monitoring.

Puts on incredibly picky hat...

Shouldn't T2 appear as 9V/240V AC rather than 240V/9V AC?

Takes off hat...

Am, yes fair point - depends rather on if you take that as a label or a part description.

I have used it as a part description rather than using it to label the connections. It is fairly obvious on T1 on the left of the diagram, but could perhaps be misconstrued on the right.

I have added a note under the diagram to clarify:

:-)