1. The relay module is a single‑channel design, with strong anti‑interference performance and stable operation. 2. All the program download ports of the WiFi module are led out to facilitate secondary development. 3. Made of high‑quality PCB materials, excellent production technology, not easy to produce false welding. 4. DC7‑12V and DC5V USB two power supply methods, suitable for various working situations such as smart home wireless control, etc. 5. The relay module is small and compact, easy to install, does not take up space, and has higher safety. Specification: Item Type: Relay Module Material: PCB Working Voltage: DC7-12V / DC5V USB Purpose: Suitable for secondary development and learning of ESP8266 Suitable Scenarios: Smart home wireless control and other How to Use: Wiring Instructions:  L, N: AC90‑250V power supply AC90‑250V to DC5V switching power supply (do not touch directly with your hands when using AC power supply) VCC, GND: DC7‑12V power supply Micro USB: DC5V USB power supply 6x6mm Button: ESP8266 reset button UART Program Download Port: ESP8266 GND, RX, TX, 5V are respectively connected to the GND, TX, RX, 5V of the external TTL serial port module, 100 must be connected to GND when downloading, and then disconnect the connection between 100 and GND after the download is complete; GPIO pin header leads to the port; Relay Output:  Normally closed, the relay is short‑connected with COM before the pull‑in, and hangs in the   after the pull‑in; COM: Public end; NO: Normally open end, the relay is suspended before being closed, and shorted to COM after being closed. Power indicator LED; Programmable LED; Relay Indicator LED: Lights up when it is closed. Package List: 1 x Relay Module3 x Pin Headers 1 x Socket Note: 1. Choose one of the two power supply modes: DC7‑12V or DC5V USB. 2. When using AC power supply, do not directly touch the AC90‑250V to DC5V switching power supply with your hands.