Stable ESP-12f WiFi module on board, 4MB large capacity flash memory. The I/O port and UART program download port of the WiFi module are all led out to facilitate secondary development. Power supply mode supports DC24V. RST reset button and a programmable button for the onboard WiFi module. Esp-12f supports the use of Eclipse/for Arduino LDE and other development tools, and provides reference programs under the Arduino development environment. Built-in 16-channel 24V/10A relay, output coupling signal, suitable for controlling the load whose working voltage is between AC 250V/DC 30V. Built-in power lamp, relay lamp, and a module with LED. Two built-in 74HC595 shift registers control the relay switch. The 16-way relay is controlled by two 74HC595 cascades, so the corresponding 595 control program is required to open and close the relay. The reference program has been provided. Burn and write port: GND, Rx, TX, and 3.3V of ESP8266 are respectively connected to GND, TX, RX, and 3.3V of the external TTL serial port module. IO0 must be connected to GND when downloading, and then disconnect IO0 and GND after downloading. Relay output terminal: NC: Normally closed end, the relay is short-circuited with com before closing and disconnected after closing; COM: Common end. NO: Normally start, the relay is disconnected before closing, and it is short-circuited with com after closing. Different batches, the product appearance and color may be different, does not affect the use Color: Green Material: PCB Type: 12V Package Contents: 1 x Relay Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to be slightly different from the real thing. The allowed measurement error is +/- 1-3 cm.