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Tuya Sandwich Power Socket Board

Last Updated on : 2022-10-26 07:01:20download

Tuya Sandwich power socket board features energy metering, output power-down, and 220V AC input. This board consists of a resistor-capacitor step-down circuit, Belling’s BL0942 energy metering IC, Everlight’s EL3H7CTA-G optocoupler, HONGFA’s relay, and Natlinear’s LN1173B332MR.

Tuya Sandwich Power Socket Board

Function and connection

  • This board uses an optocoupler to isolate your circuit from high voltage systems, providing a safe environment for personnel to work in.
  • This board is used in tandem with the Tuya Sandwich microcontroller board. It transmits control signals to the relay by setting the I/O pins on the microcontroller board, and reads data such as voltage and current measured by the energy metering IC through the UART1.

Components

This board consists of a Belling’s BL0942 energy metering IC, resistor-capacitor step-down circuit that supplies power to the energy metering IC, Everlight’s EL3H7CTA-G optocoupler, HONGFA’s relay, and Natlinear’s LN1173B332MR.

Component Description
U1 and U2 (EL3H7CTA-G) The optocoupler used to isolate the circuit from high voltage systems, preventing electric shock.
U3 (BL0942) The single-phase multifunctional energy metering IC that operates from a 3.3 V input voltage and has a calibration-free clock.
C6 (220 nF CBB) The capacitive reactance limits the current flowing through the main circuit.
U4 (LN1173B332MR) The linear regulator.
K1 (HF115F) The 5V power relay.

Pin functions

The board offers a variety of peripheral interfaces. The following table lists the pin functions.

I/O Description
3V3 3.3V input pin, used to supply power to the low-voltage circuit.
5V 5V input pin, used to supply power to the relay coil and peripheral circuit.
GND 5V and 3.3V power ground.
P24 (K1 Relay) I/O input signal, used to control the relay. When the input control signal is high level, the relay is on.
P26 (Button S1) The button S1 signal, defaulting to 3.3V. When the button is pressed, 0V is output.
P28 (Wi-Fi LED) The control signal for Wi-Fi status LED. The LED comes on at a high level.
TX_IC BL0942’s TX pin that is converted through the optocoupler is connected to RX1 on the microcontroller board with an H1 2.54 mm jumper cap.
RX_IC BL0942’s RX pin that is converted through the optocoupler is connected to TX1 on the microcontroller board with an H1 2.54 mm jumper cap.

Power requirements

  • Terminal U5: connected to 220V AC input.
  • Terminal U6: connected to a load. The relay controls the output voltage.
  • AC power supply for low-voltage circuit: 3.3V and 5V, which is isolated from the 220V AC input but not isolated from the power supply to BL0942.
  • Average current for 3.3V power supply: less than 200 mA, used to supply power to the optocoupler and button.
  • Average current for 5V power supply: less than 200 mA, used to drive the relay coil.
  • Tuya Sandwich power socket board consists of the mains-power circuit and low-voltage circuit. When power is connected, do not touch the board to prevent a possible shock.

Schematic diagram and PCB

The schematic diagram of the board:

Tuya Sandwich Power Socket Board

The PCB board:

Tuya Sandwich Power Socket Board

Things to note

  • The power socket board must be used in tandem with the microcontroller board and power supply board.
  • It consists of the mains-power circuit and low-voltage circuit. When power is connected, do not touch the board to prevent a possible shock.
  • Make sure to supply high voltage to the energy metering IC for proper operation.
  • AC power supply below 176V can cause insufficient voltage at the energy metering IC. If low voltage is required, you can adjust the resistor-capacitor step-down circuit.

Reference