Hello, I created my own Night light with all custom parts and wb8p (BK7231T) module. However I selected P-channel mosfets for the led control. Can anyone advise me on how to reverse PWM so LOW (0v) is the on state? I really prefer not to build level inversion circuit, as it just seems dumb....

I think there is already PWM_n role in OpenBeken, exactly for this purpose. Added after 37 :

Hey sorry for delay. Are you able to get ADC value to channel? If you are, then you can do: Code: text Expand Select all Copy to clipboard addChangeHandler Channel3 > 500 SetChannel 1 0 addChangeHandler Channel3 =500 then SetChannel 1 1 delay_s 0.1 goto again etc

>>21586648 Well, turns out me and ChatGPT both did not find this - THANKS!!!Now will look for a way to make the light sensor (photo-resistor in voltage divider setup) work.Any advice is welcomed!

Did you point ChatGPT towards our docs? It should be able to open few pages. I will check this in a moment. Well, BK7231 chips has one ADC pin that you can use in OBK. WB8P seem to have it marked on the silkscreen. OBK has ADC role that can read ADC value to channel. Then you can process it with scripting, depending on what you want to achieve.. Btw, how your current board looks like? I also did some DIY dimmers in the past so I am curious.

>>21586692 There is NO board, it's a SMD wire web held up with UV resin.I use custom Led arrays (one made from orange car blinker leds (PWM5), and one from cold white solar lamp(PWM1)) with appropriate current limiting (22 ohm resistor for cold white and just diode to drop 0.2v for orange). Do not worry they run well under 50% rated current, yellow ones are even on ALU PCB even though they are running at 60mA for 5 5730 leds.all leds are running off same power as MCU : 3.3v : use si2301 as led control led with 20k pull up.The body is Chinese night lamp.Light sensor is photo resistor i gt from who knows where...seems 1.5Mohm resistor was nice match match for it /or highest i had/ so now i read 3000lux at very dark at 2700 at dark when i configure the ADV as lux sensor.Still no idea what script i need Added after 23 [minutes]:Here are some pictures.Last two are original board.

I checked ALL I could find - no idea where to place script and autoexec.bat does not seem to support actions based on ADC read value.Any help ?

yes I managed to read the ADC by setting it to illuminate and channel 3.Output is inverted, but this is fine with me.Your commands did work!Thank you so much I scraped throughout all documentation and could not find this, was expecting to use GetChannel Added after 10 [minutes]:This did the trick for me:addChangeHandler Channel3 > 2900 led_enableAll 1addChangeHandler Channel3

Reversing PWM Output Logic for P-Channel MOSFETs on WB8P (BK7231T) Module

apsis 168 7

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#1 21586592 22 Jun 2025 21:11

apsis apsis

Level 6

Post #1
21586592 22 Jun 2025 21:11

Hello,

I created my own Night light with all custom parts and wb8p (BK7231T) module.

However I selected P-channel mosfets for the led control.

Can anyone advise me on how to reverse PWM so LOW (0v) is the on state?
I really prefer not to build level inversion circuit, as it just seems dumb.

There are some additional questions on how to read the Light sensor connected to ADC, but this is not as urgent.

Added after 44 [minutes]:

Chat GPT told me to go OpenBeken 1.19.x i did find compiled thing and it was horrible.

Guess i either spend time soldering or wait.

I am amazed such simple thing is not there yet...

Added after 9 [minutes]:

I use SOT-23 mosfets, so this is another hell to solder with no PCB, well i guess i have to,

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#2 21586648 22 Jun 2025 21:17

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

Helpful post? (+1)

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Post #2
21586648 22 Jun 2025 21:17

I think there is already PWM_n role in OpenBeken, exactly for this purpose.

Added after 37 [seconds]:

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.
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#3 21586683 22 Jun 2025 21:54

apsis apsis

Level 6

Topic author Helpful post? (0)

Post #3
21586683 22 Jun 2025 21:54

>>21586648 Well, turns out me and ChatGPT both did not find this - THANKS!!!

Now will look for a way to make the light sensor (photo-resistor in voltage divider setup) work.
Any advice is welcomed!
#4 21586692 22 Jun 2025 22:06

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

Helpful post? (0)

Post #4
21586692 22 Jun 2025 22:06

Did you point ChatGPT towards our docs? It should be able to open few pages. I will check this in a moment.

Well, BK7231 chips has one ADC pin that you can use in OBK. WB8P seem to have it marked on the silkscreen. OBK has ADC role that can read ADC value to channel. Then you can process it with scripting, depending on what you want to achieve..

Btw, how your current board looks like? I also did some DIY dimmers in the past so I am curious.

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 21586729 22 Jun 2025 23:21

apsis apsis

Level 6

Topic author Helpful post? (0)

Post #5
21586729 22 Jun 2025 23:21

>>21586692
There is NO board, it's a SMD wire web held up with UV resin.
I use custom Led arrays (one made from orange car blinker leds (PWM5), and one from cold white solar lamp(PWM1)) with appropriate current limiting (22 ohm resistor for cold white and just diode to drop 0.2v for orange).
Do not worry they run well under 50% rated current, yellow ones are even on ALU PCB even though they are running at 60mA for 5 5730 leds.
all leds are running off same power as MCU : 3.3v : https://www.aliexpress.com/item/1005006368811....order_list.order_list_main.69.38c61802S4btol

I use si2301 as led control led with 20k pull up.
The body is Chinese night lamp.

Light sensor is photo resistor i gt from who knows where...
seems 1.5Mohm resistor was nice match match for it /or highest i had/ so now i read 3000lux at very dark at 2700 at dark when i configure the ADV as lux sensor.

Still no idea what script i need

Added after 23 [minutes]:

Here are some pictures.
Last two are original board.
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#6 21587320 23 Jun 2025 17:26

apsis apsis

Level 6

Topic author Helpful post? (0)

Post #6
21587320 23 Jun 2025 17:26

I checked ALL I could find - no idea where to place script and autoexec.bat does not seem to support actions based on ADC read value.
Any help ?
Helpful post

#7 21587325 23 Jun 2025 17:30

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home
Helpful post? (+1)

Helpful post
Post #7
21587325 23 Jun 2025 17:30

Hey sorry for delay. Are you able to get ADC value to channel?

If you are, then you can do:
Code: text Expand Select all Copy to clipboard
addChangeHandler Channel3 > 500 SetChannel 1 0 addChangeHandler Channel3 <= 500 SetChannel 1 1

or also:
Code: text Expand Select all Copy to clipboard
again: if $CH4>=500 then SetChannel 1 1 delay_s 0.1 goto again

etc

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.
ADVERTISEMENT
#8 21587347 23 Jun 2025 18:05

apsis apsis

Level 6

Topic author Helpful post? (0)

Post #8
21587347 23 Jun 2025 18:05

yes I managed to read the ADC by setting it to illuminate and channel 3.
Output is inverted, but this is fine with me.

Your commands did work!
Thank you so much I scraped throughout all documentation and could not find this, was expecting to use GetChannel

Added after 10 [minutes]:

This did the trick for me:

addChangeHandler Channel3 > 2900 led_enableAll 1
addChangeHandler Channel3 <= 2700 led_enableAll 0

My readings are inverted due to wiring
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Topic summary

A custom night light project using the WB8P module with a BK7231T chip and P-channel MOSFETs for LED control required reversing the PWM output logic so that a LOW (0V) signal turns the LEDs on. Instead of adding an external level inversion circuit, the solution was found within the OpenBeken firmware, which supports a PWM_n role designed for inverted PWM signals. The user also integrated a photoresistor light sensor connected to the ADC pin on the BK7231T, configured as a voltage divider with a 1.5 MΩ resistor. Reading ADC values was achieved by assigning the ADC role to a channel in OpenBeken and using scripting commands such as addChangeHandler to trigger LED control based on light intensity thresholds. The user successfully implemented scripts to enable or disable LEDs depending on ADC readings, despite the inverted output due to wiring. The discussion highlights the use of SOT-23 P-channel MOSFETs (specifically the SI2301) with a 20k pull-up resistor, custom LED arrays (orange car blinker LEDs and cold white solar lamp LEDs), and the challenges of soldering without a PCB. The OpenBeken 1.19.x firmware was recommended for these features, and scripting was essential for ADC-based automation.
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Reversing PWM Output Logic for P-Channel MOSFETs on WB8P (BK7231T) Module

Reversing PWM Output Logic for P-Channel MOSFETs on WB8P (BK7231T) Module

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