Blink external LED on NodeMCU is very easy with this NodeMCU ESP8266 board as its self sufficient with everything on it. Detailed initial setup steps can be found here.

Led in itself has two terminals, anode (+ve) and a cathode (-ve). Do pay attention to it while installing it on the breadboard. You can check polarity with multimeter also. For visual understanding, the longer leg is the anode.

Also, note that every LED has different specifications and voltage requirements. You can always check its datasheet to get those and then calculate the resistance requirement accordingly.

Resistance required
= (Power source voltage – LED voltage) / Current rating of LED (amp)

So in my case its, (5-1.8)*1000/25 = 128 Ω (approx). I am using a 100 Ω resistor. Higher the resistor value, lower the brightness. At around 128 Ω it will have max supported brightness. Lower resistance value may burn it in the long run.

REQUIREMENTS

• NodeMCU ESP8266 Board
• Micro USB Cable
• LED’s
• Resistance (as per LED, use formula described below) or 100 – 200 Ω in general.
• Arduino IDE with ESP8266 board definitions & drivers installed

GETTING READY TO BLINK EXTERNAL LED

1. Install the NodeMCU board on the breadboard’s one side.
2. Install two LEDs on the breadboard with the anode (+) on D1 & D5 pin of NodeMCU while cathode (-) on the power rail.
3. Ground the same rail with resistance in series using any of the ground pins of NodeMCU.

4. Connect micro USB cable’s one end to Laptop and other to board’s USB port.
5. Open Arduino IDE and choose board NodeMCU 1.0 from Tools → Boards.
6. Set baud rate to 115200 and choose the port to which it is connected.
7. Copy the code below to IDE.
8. Go to Sketch → Upload
9. Wait for the code to get uploaded. Other blue LED near WiFi chip blinks continuously while the board is being programmed. Don’t confuse it for LED you code will blink.
10. Upon successful completion of the task, IDE will display 100% on the bottom zone and LED will start blinking.

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CODE TO BLINK EXTERNAL LED

#define LED1 D1 //Led in NodeMCU at pin D1
#define LED2 D5 //Led in NodeMCU at pin D2 

void setup() 
{
 pinMode(LED1, OUTPUT);   //LED1 D1 pin as output 
 pinMode(LED2, OUTPUT);   //LED2 D5 pin as output 
}
 void loop() // runs/loops below code infinitely
{
 digitalWrite(LED1, HIGH); //turn on LED
 delay(300); 
 digitalWrite(LED1, LOW); //turn off LED
 delay(300);
 digitalWrite(LED2, HIGH); //turn on LED
 delay(300);            
 digitalWrite(LED2, LOW); //turn off LED
 delay(300); 
//delay defines duration in ms for which LED is on/off or in actual way, its //the duration for which program waits here on this line of code 
}

Some Basic Things with NodeMCU ESP8266

Setup Arduino for NodeMCU programming

Blink Onboard Blue Colour LED

Interface With Relay (for controlling AC/DC devices)

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Get NodeMCU ESP8266 from Amazon India