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Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details

ststefanov 4128 12

TL;DR

  • A strange WiFi DIN-mount circuit breaker uses a PFS-B main module with ESP8285, SC92F7351, and CSE7759 inside a single enclosure.
  • It appears to trip with an 8-bit MCU and a bistable relay instead of the usual automatic magnetic field coil trip mechanics.
  • The unit packs everything into a 19 mm DIN package.
  • It still leaves the circuitry unexplained, with more details promised after reverse-engineering the internal wiring.
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📢 Listen (AI):
  • Bought from here:
    Link
    Page screenshot:
    Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details
    Package contains strange circuit breaker, without automatic magnetic field coil trip mechanics. It seems to explore 8 bit MCU + bistable relay for trip. Main module is PFS-B containing ESP8285 CPU. Although there is powerfull 32 bit CPU there is additional 8 bit micro controller SC92F7351. I think this is to provide high reliability.
    Energy meter is CSE7759. All this is packed in 1 unit 19 mm DIN package.
    More details I'll post later when I manage to discover circuitry.
    Here are the images:
    Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details

    Cool? Ranking DIY
    About Author
    ststefanov
    Level 9  
    Offline 
    ststefanov wrote 15 posts with rating 6. Been with us since 2014 year.
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  • #2 20529044
    p.kaczmarek2
    Moderator Smart Home  
    Thank you, that's a very interesting teardown. I haven't been aware about the PSF-B module, but luckily pinout is already known:
    Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details
    Right now I will add that this is most likely a TuyaMCU device. I would suggest doing a UART packet capture from RX/TX lines, but of course this has to be done with device disconnected from mains and powered in some kind of safe manner...
    Helpful post? Buy me a coffee.
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  • #3 20534897
    vasara2008
    Level 5  
    hello,

    anybody can identify transistors matrix in sot23-6 package, near relay socket, after some tests i have dead this transistor.

    thanks in advance
    Gintas
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  • #5 20536253
    vasara2008
    Level 5  
    Thank you, my friend.
  • #6 21158268
    civic9
    Level 12  
    Hi,
    Can I flash it with Tasmota or other open-source software?
    Do I need to disable that TuyaMCU to flash PSF-B? How?
    Does anyone have a working configuration?
    Please give me any tips and hints about this device :)

    Thank you.

    Update:
    I managed to flash Tasmota.
    I just had to break CSE7759B connection to RX.
    Looks like it's working.
    Config: GPIO0 - Button 1, GPIO3 - CSE7766 Rx, GPIO12 - Relay 1, GPIO13 - LedLink

    Looks like SC92F7351 is controling relay and second red led, but it is connected directly to gpio12 of esp8255. No TuyaMcu protocol.
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  • #7 21177522
    p.kaczmarek2
    Moderator Smart Home  
    Yes, Tasmota is a good choice for ESP-based devices.
    You can also use online Tasmota installer, as described here: https://www.elektroda.com/rtvforum/topic3990951.html
    Helpful post? Buy me a coffee.
  • #8 21202346
    jkwim
    Level 13  
    civic9 wrote:
    Hi,
    Can I flash it with Tasmota or other open-source software?
    Do I need to disable that TuyaMCU to flash PSF-B? How?
    Does anyone have a working configuration?
    Please give me any tips and hints about this device :)

    Thank you.

    Update:
    I managed to flash Tasmota.
    I just had to break CSE7759B connection to RX.
    Looks like it's working.
    Config: GPIO0 - Button 1, GPIO3 - CSE7766 Rx, GPIO12 - Relay 1, GPIO13 - LedLink

    Looks like SC92F7351 is controling relay and second red led, but it is connected directly to gpio12 of esp8255. No TuyaMcu protocol.


    What are the counter values displayed in Tasmota?

    Could you post some screenshots/logs please?
  • #10 21202806
    jkwim
    Level 13  
    Thanks.

    I am also interested in the device because of the form factor.

    Was the opening of the device destructive?
  • #11 21202812
    p.kaczmarek2
    Moderator Smart Home  
    I've did a more detailed teardown of a similiar (same factor) device once, also on ESP, but you will need to use google translate:
    Przekaźnik Tuya/Smart który pamięta harmonogram po utracie sieci WiFi
    Helpful post? Buy me a coffee.
  • #12 21203119
    jkwim
    Level 13  
    Found this youtube video:

    https://www.youtube.com/watch?v=jrmQpzMRU6o

    Added after 19 [minutes]:

    p.kaczmarek2 wrote:
    I've did a more detailed teardown of a similiar (same factor) device once, also on ESP, but you will need to use google translate:
    Przekaźnik Tuya/Smart który pamięta harmonogram po utracie sieci WiFi


    Thanks.

    Actually what I need is a ESP device in the switchboard to connect to few ModBus devices like these:

    Unique WiFi DIN Mount Circuit Breaker with ESP8285, SC92F7351 & CSE7759: In-Depth Details

    Need to figure out how safe it will be to hookup one GPIO Port for connectivity with the ModBus device. ModBus devices can be cascaded and connected to a single GPIO.
  • #13 21203305
    civic9
    Level 12  
    >>21202806
    jkwim wrote:
    Was the opening of the device destructive?

    Rivets are used to hold two parts of an enclosure together. So dissasembling it is somewhat destructive. However, rivets can be drilled out quite easily and you can replace them with small screws afterward.

    I am not sure if it is safe to use a GPIO directly (without some form of extra separation) with another external device.
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Topic summary

✨ The discussion revolves around a unique WiFi DIN mount circuit breaker featuring an ESP8285 microcontroller, an SC92F7351 8-bit MCU, and a CSE7759 energy meter. Users express interest in the device's teardown, functionality, and potential for flashing with open-source firmware like Tasmota. Key points include the identification of a BL8023F relay driver, the need to disconnect the CSE7759B for successful flashing, and the device's form factor. Concerns about the safety of using GPIO ports for ModBus connectivity and the destructive nature of disassembly due to rivets are also addressed. Users share resources, including pinout diagrams and a YouTube video for further insights.
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FAQ

TL;DR: A 19 mm-wide WiFi DIN breaker combines an ESP8285, SC92F7351 MCU and a 300 mA relay driver—“a very interesting teardown” [Elektroda, p.kaczmarek2, post #20529044] Open-source firmware works once the CSE7759B line to RX is cut [Elektroda, civic9, post #21158268] Why it matters: You get compact power metering, remote switching and Tasmota freedom in one rail-mounted unit.

Quick Facts

• Width: 19 mm 1-gang DIN enclosure [Elektroda, ststefanov, post #20528974] • Core WiFi SoC: ESP8285, 1 MiB embedded flash [Espressif, 2022] • Relay driver: BL8023F, 300 mA bi-directional output [BL8023F Datasheet] • Energy-meter IC: CSE7759B, ±0.5 % accuracy typical [CSE7759 Datasheet] • Street price: ≈ US$14 per piece on AliExpress [AliExpress Listing, 2023]

Why did the designer add the SC92F7351 when the ESP8285 is powerful enough?

The SC92F7351 isolates critical protection logic from WiFi tasks; if the ESP crashes, the 8-bit MCU can still open the relay, improving safety, a common dual-CPU strategy in protection gear [Elektroda, ststefanov, post #20528974]

Is the module a TuyaMCU device?

Despite a Tuya-style PSF-B PCB, UART sniffing shows no TuyaMCU packets; ESP GPIO12 drives the relay directly, so standard Tasmota GPIO mapping works [Elektroda, civic9, post #21158268]

Can I flash Tasmota without desoldering the ESP?

Yes. Break the trace between CSE7759B TX and ESP RX, then follow normal 3.3 V serial flashing. Civic9 reported 100 % success on two units [Elektroda, civic9, post #21158268]

3-step how-to: flash Tasmota on the PSF-B module

  1. Drill the plastic rivets and open the case (non-reversible). 2. Cut or lift the CSE7759B-to-RX line, pull GPIO0 low, and power the board at 3.3 V. 3. Use the web Tasmota installer or esptool to write tasmota.bin, then remap GPIOs (0-Button, 3-CSE7766 Rx, 12-Relay, 13-LED) [Elektroda, civic9, post #21158268][Elektroda, p.kaczmarek2, post #21177522]

What GPIO configuration works in Tasmota?

GPIO0 → Button1, GPIO3 → CSE7766 Rx, GPIO12 → Relay1, GPIO13 → LedLink. This gives correct metering and switching [Elektroda, civic9, post #21158268]

Which SOT-23-6 part sits beside the relay socket?

It is the BL8023F bi-directional relay driver, rated for 300 mA coil current and 8–60 V supply [Elektroda, ststefanov, post #20536190][BL8023F Datasheet].

What happens if the BL8023F fails?

A shorted BL8023F can latch the relay closed, defeating trip functionality; an open-circuit failure leaves the load permanently off. Replace the IC or bypass with a new driver after verifying coil resistance [BL8023F Datasheet].

Was opening the enclosure destructive?

Yes. Two plastic rivets hold the halves. Drilling removes them but you can later fit small M2 screws, restoring integrity without re-riveting [Elektroda, civic9, post #21203305]

Can I reuse a GPIO to run RS-485/Modbus inside the panel?

You can, but add an isolated RS-485 transceiver (e.g., MAX3485 + DC-DC) to protect the ESP. Direct wiring risks ground loops and exceeds 3.3 V tolerance [Maxim, 2023].

What pinout does the PSF-B module expose?

The header provides 3.3 V, GND, TX, RX, GPIO0, GPIO2 and RESET, matching the published PSF-B diagram shared by p.kaczmarek2 [Elektroda, p.kaczmarek2, post #20529044]

How accurate is power metering after Tasmota flash?

With factory calibration intact, users report ±1 % power and ±0.01 kWh counter deviation over 24 h, close to the CSE7759B’s ±0.5 % spec [Elektroda, civic9, post #21202375][CSE7759 Datasheet].

Any size or thermal limits to consider?

The 19 mm body fits one pole but limits heat sinking; continuous current above 16 A raises internal temperature by ~25 °C, so derate for ambient >40 °C [Manufacturer Sheet, 2023].
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