NodeMCU electronic switch

Here’s a really easy demonstration of how you can control outputs on the NodeMCU with a simple web interface. The NodeMCU runs as a simple web server, writing a control panel interface directly as HTML.

Hardware

The circuit is very simple, just four LEDs with resistors wired to outputs of the NodeMCU.

wiring diagram
wiring diagram

Here’s the wiring I used, which matches the code.

  • yellow – D1 = GPIO5
  • green – D2 = GPIO4
  • blue – D3 = GPIO0
  • red – D7 = GPIO13

In Arduino code, GPIO numbers map to Arduino digital outputs, so to turn on yellow LED use digitalWrite(5, HIGH)

NodeMCU circuit
NodeMCU circuit

Software

  1. Get the code example (esp8266ledControl.ino) and edit to add your wifi name and password to the code.
  2. Board type in Arduino IDE is ‘Node MCU 1.0 (ESP-12E Module)’
  3. You will need to set up your Arduino IDE to work with the NodeMCU. A good guide can be found at https://www.circuito.io/blog/nodemcu-esp8266/ (go to the last section Programming NodeMCU with Arduino IDE)
  4. Upload the code to the NodeMCU.
  5. When it has finished loading, quickly open the Serial Monitor, set the baud rate to 115200.
  6. Wait until the device joins the WiFi network, and note the IP address it obtains.
  7. Enter this address in a web browser, and the interface will load.
  8. Now you can turn on and off the various coloured LEDs by clicking on the respective buttons.
web interface
web interface