Totally unexpected circuitry.

A 5V memory backup capacitor might work. Not sure what the quiescent current draw is.

Big Clive

The battery is dead inside, what capacitor would be suitable to replace it?

Claudio Zodio

The chip itself can provide accurate frequency data. I think it's just to tell the processor when the unit is powered so it can activate the display and initialise the power monitor chip.

Big Clive

Was thinking, that one transistor that turns on every halfwave might also be used to get the Hertz frequency, what do you think?

Cleveland Prescott

AD make low pin-count devices which similarly sample current & voltage 100s of 1000s of times a second and calculate power for any arbitrary load waveform. Now imagine if you will, a device which replaces the hot busbar in a UK style consumer unit containing a shunt and one such chip for each MCB/RCBO plus a single micro and which transmits the data via IR to a sensor poked into the consumer unit. High accuracy monitoring of individual circuits without using lame snap-on current transformers

Gordo

Terrific teardown Clive, thank-you! HT1621B I know well. Bit slow, but perfectly dependable. Strange clocking scheme, different read and write clocks. I've had instances where it remembers the LCD contents on a stupid low VDD and you power it up later and "eh? why's that still there?" Interestingly both boards are rather well done single-sided (if by well done we allow running two tracks under a 1206). In the case of the LCD board this leads to a very pleasing segment fan-out. However, unless the LCD design takes this into account, it could lead to messy firmware!

Mike Page

The key is cleanliness. I designed a big-ass LCD with 512 segments (4 driver ICs) around the same time. Always a bit dodgy if I needed to disassemble tnen re-assemble by hand. Much better if not disturbed.

Mike Page

I was going to replace my old 2000MU but after reading a few of the reviews I will just stay with the old basic Energy Monitor that is only used every blue moon on untrusted devices new to the office.. cheers tho.

I've seen this similar but more sophisticated model for a couple of pounds more. It displays a history of power consumption by means of bar graphs and, supposedly, CO2 emissions. https://www.amazon.co.uk/Nevsetpo-Consumption-Electricity-Calculator-Protection/dp/B07JN4SDMQ

Back in the 90s & 00s I worked for Nokia and we were always warranty replacing zebra strips. Interesting circuit on this...I like it I might get one

LANDLINEMAN.com

No. I just got lucky. It'll probably go back downhill from here.

Big Clive

The snag is that as soon as you touch those solder joints it may skew the calibration. Of greater interest is replacing it with a thinner wire with ten times the resistance to make the unit ten times as accurate on smaller loads.

Big Clive

Have we reached the event horizon where good quality merchandise is as cheap or even cheaper than poor quality? This was 3 in a row from eBay!

Mike Bird

Thank you Clive. I've ordered one.

That's more pages than a Bang & Olufsen bit of kit.

Andrew Donaldson

I saw you using one of these a while back, so unable to find a Hopi for sale, I bought on- I was really pleased with the performance (it cost £8.42 free postage from uk supplier)

Mike Hughes

I have these units 4 of them, even have some in my workshop, I’ve had these for about 4 years now, used it as a reference on where about it was and not absolute value, it also monitors power frequency, ideal for tweaking generator voltage frequency,

Mike

I used to have a very similar unit however it used a connectorized cable instead of a soldered cable between the two PCBs. The thing failed very quickly; the autopsy revealed the gauge of the wire was too thin and it just slid out of the crimped sockets. Replaced it with a SONOFF POW R2 with Tasmota firmware; an amazing example of open source firmware.

WizardTim

it is pretty common to mod these (or the kill-a-watt branded units) with a bluetooth or wifi module so you can safely do logging on a PC, since it is 3.3v serial uart referenced to the live input.

Good to know they are accurate, I've had one for a year or so, I knew the voltage matched my Fluke but other than that assumed it was rough and ready, will probably use it more often after watching this.

The Tinkering Shed

It looks like the current bridge line could use some good "lead" solder.

That depends on where you are in the world as local sellers will have your matching plug and socket arrangement.

Big Clive

Much longer than expected. The first version didn't go into enough detail on the voltage and current measuring, so I had to do it again as it seemed logical to include that info on a device that has the sole purpose of doing that.

Big Clive

To be fair Clive, that was a very impressive, detailed teardown... how long have you spent on this baby? I really enjoyed this one!

I have one, It's gonna be in bits tomorrow... probably never work again. Thanks for the inspiration though Clive!

I've been thinking about getting one of these too, I guess I'll do it now.

Earl Plotner

But … but … but where's the link to the fleBay sailor?