Tuya Smart WiFi Ceiling PIR Motion Detector PST-HW400B: Pin Configuration & Power Saving Tips

Question

Hello! Recently I started to dive into the IoT topic and at the moment I'm dealing with: Name: Tuya Smart WiFi Wireless Ceiling PIR Infrared Movement Motion Detector Model: PST-HW400B This is how it looks inside: Using tuya-cloudcutter I was able to install OpenBK7231N_UG_1.15.365.bin firmware...

p.kaczmarek2 · Answer

Hello, please first narrow down the possible pin candidates by looking at the PCB tracks and/or by checking with multimeter (there are traces going to PIR sensor, you can check them with multimeter if you scrap the soldermask from the board, but do not of course cut the tracks accidentally).
Then, in openbeken, you can set pin candidates to, for example, digitalInput (dInput) or maybe to dInput_noPullUp (I don't know at the moment), set separate channel for each pin candidate and try to trigger the sensor and observe which channel changes.

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.

uzverj · Answer

It is not so easy a task to track the connection between pins. Some of the traces are located under elements. Okay let's moving forward step by step.
At the moment I was able to trace some connections and made some voltage measurements. This is a draft and if something is not clear please ask the question.

PIR BS612 module - voltage measurements - connection
1(SENS) - 0v1
2(OEN) - 1v6
3(VSS) - 0 (GND)
4(VDD) - 3v3
5(REL) - 3v3 -> R15 -> CB3S (pin 13) P8
6(ONTIME) - 0v5

My electronic skills are not so good. This is what I was able to trace and show on the PCB.
Up side

Down side

uzverj · Answer

Is this enough to start some experiments with PIN configuration?
At the moment I don't understand what PIN I should configure with what parameters. Can you suggest some options? It will be good if they will be with real examples. And where I should see the changes?

p.kaczmarek2 · Answer

Very good reverse engineering. My only question would be, why do you have ADC3 twice?

Hmm CB3S docs clearly shows which pin is which Px role.

If you think that, for example, P26 is a input of PIR sensor, they you can try setting P26 role to "dInput" and then watch channel 0 value on Gui (it should show up), is it changing to 1 if you try to trigger sensor?

about PIR sensor:

Quote:

This PIR sensor itself is pretty straightforward and works out of the box. Simply apply power 5V – 12V and ground. The sensor output goes HIGH when motion is detected and goes LOW when idle (no motion detected).

uzverj · Answer

Regarding PIR, as I understand correctly it is not so simple it is working on 3V. Please check the link.
https://evelta.com/pyroelectric-infrared-sensor-6pin-3v/

According to my investigations PIR pin 5(REL) connected to CB3S pin 13 (with mark P8) through resistor R15.
I made measurements and I see 3.3v on PIR pin 5 (REL) and CB3S pin P8 constantly.
Unfortunately I can't receive any output from the PIR. I was trying to configure "dinput", "dinput_n", "dInput_noPullUp" and "dInput_noPullUp_n" in configurator for field P8.

I was able to light the diode assigning LED_n to P26.

p.kaczmarek2 · Answer

I don't know this specific sensor, but there is a following description: so maybe it's worth trying to set ADC role one one of the connected pins? Remember to set ADC channel to something else than dInput channel if you have one, because in this case two input pins would try writing to the same channel and you'd see seemingly random changes on gui.

uzverj · Answer

Thanks for your assistance!
Now I know how this PIR PIN's should be configured to send information about motion detection.

It took some time, because of PIR behavior. When PIR reacts to motion it changes signal on Channel1 from 0 to 1 and holds it for 30 seconds approximately.
According to my understanding to make this time shorter I need to cut off resistor R10 and connect PIR PIN 6 (ONTIME) to GND. Then ONTIME should be 2 seconds. Can you comment this?

I added the PIR to my Home Assistant through "Home Assistant discovery" and it appeared in HA as a device with two options "Sensor" and "Control". When I click on "Control" PIR receives the command and switches Channel1 from 0 to 1. Is it possible to block this on PIR side?

With original firmware PIR is able to show Battery level. Do you have any suggestions how Battery level can be configured in OpenBeken firmware?

uzverj · Answer

It is enough to disconnect power from resistor R10 and now ONTIME is 2 seconds. This means that when motion is finished value for Channel1 will be set back to 0 in 2 seconds instead of 30 seconds.

AntonShylo · Answer

>>20425368 .Thanks a lot! It really works better and is quicker to respond.Has anyone encountered this phenomenon where the sensor starts blinking the red LED for about 15-20 seconds and doesn't respond to anything, and then continues to work normally?

Marko121 · Answer

Hello.
I have programmed myself such a wifi pir detector with the file OpenBK7231M_QIO_1.17.606 BK7231Flasher programming was successful, but how can I now access this detector and set the ports ? (I do not have a home assistant) Is it possible to connect directly with the phone and set up these inputs, how do I do this?
Second question, will a detector with this software only work with home assistant or with any other software?

Regards

Tuya Smart WiFi Ceiling PIR Motion Detector PST-HW400B: Pin Configuration & Power Saving Tips

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