[BK7231T/WB2S] Arlec PC44HA - Bunnings Outdoor IP44 Smart Plug w/ Energy Monitoring

Hello,

I was hoping for some help in regards to this plug.

Product in question:
https://www.bunnings.com.au/arlec-grid-connect-smart-ip44-heavy-duty-timer_p0273373


Teardown (Not my pictures - credit to SleepingNerd from Reddit): https://imgur.com/gallery/k73TnCq


I extracted the Tuya Config using the Easy Flasher and was able to convert it to the following OBK template:


However, I found I had to manually change pin 24 to BL0937SEL_N in order to get the voltage and current to read correctly.

Now that I believe it's setup correctly... when I compare it to a different energy monitoring plug, there are some anomalies with the voltage monitoring stats. Whenever load is applied (a heat pump hot water system) I have found that the voltage will increase by a few volts but with no load, the voltage readings are almost exactly the same as the other plug.



I just wanted to ask if this is normal behaviour of electronics and house wiring or is it down to a faulty plug or even poor calibration by me?

Hello, thank you about that information related to BL0937SEL_N . If you have latest OBK version, you may also attach the Tuya Config binary downloaded from Web App -> Flash tab, but take care, it may restart your device during download.
Regarding your issue, first thing you can do is just double check the measurements. I assume you have calibrated your devices, right? So you must have an energy meter you've used for calibration? Then you can check if this meter is giving similar readings with voltage drop. Then, how much power do you draw when voltage drop happens? Is your entire wiring on the way to the load rated for at least more than load power+some safety margin? The small voltage drop at large loads is normal, although I wouldn't myself judge what exact drop is allowed, please consult a professional electrician on site if you are in doubt.
Here's somewhat related video and explanation why voltage drops: https://www.youtube.com/watch?v=hPHLxi9qBH8&ab_channel=JohnWard

I've added the Tuya Config to the opening post.

I unfortunately don't have a proper energy meter for calibration. What I did was use another smart energy monitoring plug (not flashed, still on Tuya) plugged directly next to this one. I used a lamp with a 20W globe in the Tuya smart plug, recorded the values, quickly switch the lamp to this flashed plug and calibrated it with the recorded values. I know it might not be the best way to calibrate but for now I'm more concerned about the power usage in Watts and it seems accurate enough.

The funny thing is, in that screenshot, the flashed plug is the blue line. Whilst I know voltage drops are normal, what's actually happening here is the voltage is increasing by 3-5 volts under load. My electrical knowledge is very limited but I thought if the voltage changes, then the other plug that's monitoring the same circuit will also see the same change? The internal house wiring to the load is definitely rated for the load + safety margin (it's a 20A circuit with Australia voltage being 230-240V, it should be rated to 4.6kW).

A voltage increase? Sorry, I was certain you're talking about voltage drop. I haven't seen anything like that, but I've seen strange measurements when you do wrong calibration.
For example, if you use BL0937SEL_N instead of BL0937SEL, when it's not needed, and you force-calibrate current value as voltage, etc, etc, you may get that kind of behaviour..

Do you have a multimeter to at least verify the voltage measurement? That would help a lot.

That being said, I have decoded your Tuya config:


and I compared it with LSPA9 config:

and one of them has sel_pin_lv 1, second 0, so you most likely have config correct.... your configuration looks good in general. Next step to do is to get cheap 10$ or so multimeter and check. Or borrow one from friend. There is no need to guess.