A great set of tools to develop ESP8266.NodeMCU is built based on the mature ESP8266 technology to take advantage the abundant resources available on the web.NodeMCU has ESP-12 based serial WiFi integrated on board to provide GPIO, PWM, ADC, I2C and 1-WIRE resources at your finger tips, built-in USB-TTL serial with super reliable industrial strength CH340 for superior stability on all supported platforms.ESP8266 is a highly integrated chip designed for the needs of a new connected world.It offers a complete and self-contained Wi-Fi networking solution, allowing it to either host the application or to offload all Wi-Fi networking functions from another application processor.ESP8266 has powerful on-board processing and storage capabilities that allow it to be integrated with the sensors and other application specific devices through its GPIOs with minimal development up-front and minimal loading during run-time.Its high degree of on-chip integration allows for minimal external circuitry, and the entire solution, including front-end module, is designed to occupy minimal PCB area.5V Relay Module 4-Channel This is a 5V 4-Channel Relay interface board. Be able to control various appliances, and other equipments with large current.It can be controlled directly by Micro-controller (Raspberry Pi, , 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic).5V 4-Channel Relay interface board, and each one needs 50-60mA Driver Current. Equiped with high-current relay, AC250V 10A ; DC30V 10A.Indication LED's for Relay output status. Application: Supports all MCU control, The industrial field, PLC control, Smart home control.