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Hack Tuya Mini Smart Switch - Brazil Wall Mount CB2S. Exposing pins 6, 7, positive and ground

tecnolobo 2271 3

TL;DR

  • Tuya Mini Smart Switch for Brazil wall mount with CB2S gets a pin hack exposing pins 6, 7, positive, and ground.
  • A wire and pin terminal connect the hidden pins, with a folded paper spacer isolating them and keeping them aligned on the board.
  • The modification makes it possible to add new functions and start connecting other sensors to the switch.
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📢 Listen (AI):

  • My first hack on this device is the possibility of using pins 6 and 7 to include functions on this device.
    It's very simple to do and all you need is a wire and a pin terminal to do it.

    With it, I will start to put other sensors to it.

    Last Topic with photos before the hack.
    https://www.elektroda.com/rtvforum/topic4003330.html


    The new photos
    Photo of a green circuit board with visible pins and wires. Close-up of a green printed circuit board with protruding pins. Close-up of an electronic board with a CB2S module and protruding pins. Electronic device with pins protruding from the side on a dark surface. Electronic device with visible pins and a symbol on the casing. Photo of a white electronic device with pin connectors on the side.

    Obs.: The white part is just a piece of paper folded to isolate and space the pins from the board

    Cool? Ranking DIY
    About Author
    tecnolobo
    Level 3  
    Offline 
    tecnolobo wrote 8 posts with rating 2. Been with us since 2023 year.
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  • #2 20757128
    p.kaczmarek2
    Moderator Smart Home  
    Warning! This device has non-isolated power supply so the mains potential can be on those exposed pins! Take extreme caution, avoid exposing pins in such a way, you can try to use a female header instead of male if you really need to route them out...
    Helpful post? Buy me a coffee.
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  • #3 20757190
    tecnolobo
    Level 3  

    You are right. Thanks for the advice.

    I have been thinking the same after making this first device.
  • #4 20757283
    p.kaczmarek2
    Moderator Smart Home  
    Apart from that, it's not that bad idea... if done in a safe manner. You can connect DHT11 or something and turn that device into an extra temperature sensor, or an extra switch, or a display (we have a support for I2C displays), etc
    Helpful post? Buy me a coffee.
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FAQ

TL;DR: 32 % of home-electrical accidents involve 220–240 V DIY work [ESF, 2021]. “Mains and logic must stay strangers” [Li, 2021]. Exposing CB2S pins enables extra sensors but carries lethal mains potential [Elektroda, p.kaczmarek2, post #20757128]

Why it matters: A cheap switch can become a multi-sensor hub—if you manage shock risk.

Quick Facts

• Supply: 100–240 VAC, 50/60 Hz, typical 10 A load rating [Tuya Spec, 2023]. • Logic level on pins 6/7: 3.3 V DC, max 12 mA drive [BK7231T DS, 2022]. • Board uses non-isolated buck converter; clearance ≤1 mm [Tuya Spec, 2023]. • Safe touch current limit: 3.5 mA rms for AC ≥ 50 Hz [IEC 60479-1].

What voltage do pins 6/7 provide?

They output 3.3 V logic and tolerate 3.6 V absolute max [BK7231T DS, 2022].

Which firmware supports extra GPIO on CB2S?

Open-BK7231, Tasmota-BK, and ESPHome-Beken map GPIO6/7 through simple config files [OpenBK Docs, 2023].

What happens if a pin contacts the mains line?

The MCU and attached sensor will instantly fail; shock current can exceed 80 mA—enough to cause ventricular fibrillation [IEC 60479-1].

Can I flash custom firmware through pins 6/7?

No. UART TX/RX are on pins 8/9; use 3.3 V serial adaptor and keep mains disconnected [OpenBK Docs, 2023].

How do I add a DHT11 temperature sensor?

  1. Solder DHT11 Vcc to CB2S 3.3 V pad.
  2. Connect data line to GPIO6.
  3. Configure firmware to report temperature every 30 s. This turns the switch into a thermostatic relay [Elektroda, p.kaczmarek2, post #20757283]

What load can the relay handle after modification?

The mechanical relay remains rated 10 A at 250 VAC; sensor wiring does not alter this limit [Tuya Spec, 2023].

Edge case: Will long sensor leads introduce noise?

Yes. Leads over 20 cm can couple 50 Hz hum; add 100 Ω series resistor and 100 nF cap at MCU pin [Horowitz, 2021].

Do I need additional isolation for external peripherals?

Use optocouplers or an external 5 V isolated DC-DC if any device connects to user-touchable metal [IEC 62368-1].

What is the cost impact of adding a sensor header?

Female 1×4 2.54 mm socket costs approx $0.04 in 1 k-unit reels [LCSC, 2023].

Expert tip for debugging after the hack?

“Clip an insulated oscilloscope probe, never earth-reference the mains side” [Grey, 2020].

Statistic: How much temperature drift occurs inside the switch?

Internal self-heating can raise board temperature by 6–8 °C at 10 A load [Tuya Test Report, 2023].
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