[BK7231T / WB2S] Teardown generic tuya Smart Plug with Energy Meter (BL0937)

elbuit 2781 4

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Post #1
20415945 31 Jan 2023 23:42

Hi everyone.
I would like to add a teardow of a generic tuya smartplug based on a wb2s.
I have bought this device some time ago from aliexpress:

It came with tuya 1.3.5 and I installed OpenBeken using tuya cutter for a BK7231T and selected the Generic Tuya NAS WR07W 16A smart plug.
Seems quite similar to LSPA7 https://www.elektroda.com/rtvforum/topic3932742.html#20300613 or Model: PE-01E IP44 https://www.elektroda.com/rtvforum/topic3927458.html
From outside is identical to LSPA9, but the led is blue instead of purple such as LSPA9.

It is based on a WB2S with BK7231T and a BL0937 to monitor electrical parameters such as voltage, intensity and power consumption.

Unfortunatelly there is not brand or label on the outside or even on the PCB.

Button is connected to PIN 1TX
LED(negative) is connected to PIN PWM0

I've used configuration from Model: LSPA7 and modified button pin to 11
Pin 6: WifiLED_n on channel 0
Pin 7: BL0937CF on channel 0
Pin 8: BL0937CF1 on channel 0
Pin 11: Button on channel 0
Pin 24: BL0937SEL on channel 1
Pin 26: Relay on channel 0

I followed this guide: https://www.elektroda.com/rtvforum/topic3887748.html to calibrate the device.
I didn't have a power meter close so I'll use my multimeter as an approach to calibrate this with a 100W bulb as a load.
Without load it measures:
Quote:
BL0937 Voltage=194.169738, Current=0.000000, Power=0.000000

But multimeter shows 227V, so in the log tab of the app I entered this value:
Quote:
VoltageSet 227

And got Voltage correction:
Quote:
Info:EnergyMeter:VoltageSet: you gave 227.000000, set ref to 0.145886

So, I went on and turned on the bulb
Quote:
BL0937 Voltage=227.583541, Current=0.358631, Power=72.000000

Voltage is corrected but not power and current
Power should be 100W so in the log tab I did the same with power:
Quote:
PowerSet 100
Info:EnergyMeter:PowerSet: you gave 100.000000, set ref to 1.666666

If we consider P=V*I, current should be 100/228=0.44A
Quote:
CurrentSet 0.44
Info:EnergyMeter:CurrentSet: you gave 0.439999, set ref to 0.012941

Theese corrections will be added automatically, so you won't need the following steps.
Thanks to p.kaczmarek2 for the help.

Spoiler:

So I got 3 corrections for BL0937 chip:
Quote:
VREF 0.145886
IREF 0.012941
PREF 1.666666

It's time to make these values permanent, so in app page filesystem tab I created a autoexec.bat file and added these lines:

Code: text Expand Select all Copy to clipboard
startDriver BL0937 VREF 0.145886 IREF 0.012941 PREF 1.666666

The only thing that I couldn't make work is enable or disable relay when I push the button.
But I think that I missed something because I am a OpenBeken newbie.

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elbuit elbuit

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#2 20416077 01 Feb 2023 06:31

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home
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Post #2
20416077 01 Feb 2023 06:31

Hello, thank you for the teardown. Here are my hints:
elbuit wrote:

Code: text Expand Select all Copy to clipboard
startDriver BL0937 VREF 0.145886 IREF 0.012941 PREF 1.666666

Hmm since several months it's no longer required to save REFs by hand, they are saved automatically like in Tasmota.

elbuit wrote:

The only thing that I couldn't make work is enable or disable relay when I push the button.
But I think that I missed something because I am a OpenBeken newbie.

Configuration looks 100% correct. I'd rather say that your button is not on P10 in reality. Maybe just try brute-forcing all pins and see which reacts?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#3 20416310 01 Feb 2023 10:01

elbuit elbuit

Level 6

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Post #3
20416310 01 Feb 2023 10:01

p.kaczmarek2 wrote:
Hello, thank you for the teardown. Here are my hints:
Hmm since several months it's no longer required to save REFs by hand, they are saved automatically like in Tasmota.

Edited.

p.kaczmarek2 wrote:
Configuration looks 100% correct. I'd rather say that your button is not on P10 in reality. Maybe just try brute-forcing all pins and see which reacts?

Brrr, I followed the wires and the button went to 1TX instead of 1RX.
Edited and corrected in the main post.

Thanks for your help.
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#4 20416322 01 Feb 2023 10:06

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #4
20416322 01 Feb 2023 10:06

Okay, so it has different pin for button.

Now, we already have a LSPA9-like looking plug in our templates list. Are you able to give me some specific info how to tell between old LSPA and that plug? Maybe there was some kind of model name on case, or on packaging, etc? Or are they virtually the same from outside?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
#5 20417417 01 Feb 2023 20:07

elbuit elbuit

Level 6

Topic author Helpful post? (0)

Post #5
20417417 01 Feb 2023 20:07

p.kaczmarek2 wrote:
Okay, so it has a different pin for the button.

Now, we already have a LSPA9-like looking plug in our templates list. Are you able to give me some specific info on how to tell between the old LSPA and that plug? Maybe there was some kind of model name on the case, or on packaging, etc? Or are they virtually the same from outside?

I bought this from aliexpress, but now it is not available:
https://es.aliexpress.com/item/1005001845474874.html

Unfortunately, there is no brand or label on the outside or even on the PCB.

From outside it is identical to LSPA9, but the led is blue instead of purple such as LSPA9.

But this device is a WB2S with a BL0937 meter.

I've tested with the parameters of the first post and it works really fine

If I cut off wifi from my AP, the led starts blinking but when it reconnects the led stays on without blinking.

Button OK
Wifi led OK
relay OK
energy meter OK

@p.kaczmarek2 thanks for your help and for OpenBeken.
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