How to make a 5-volt relay work with NodeMCU?

Question

I have hooked up 2 channel 5-volt relays with NodeMCU v1.0 as shown in the fritzing below.

Relay are powered with a different power source than NodeMCU.

As of now, I am powering the NodeMCU from my laptop and the relay board from a 5-volt battery.

Below is the code I have written:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

const char* ssid = "said.";
const char* password = "secret";
ESP8266WebServer server ( 80 );
const int led = 13;
const int outputLed = 12;

void turnOnRelayOne(){
  digitalWrite (outputLed, 1);
  digitalWrite (5, HIGH); //GPIO 5 // Relay 1
  server.send (200, "text/html", "Relay 1 turned on.");
  digitalWrite (outputLed, 0);
}

void turnOnRelayTwo(){
  digitalWrite (outputLed, 1);
  digitalWrite (4, HIGH); //GPIO 4 // Relay 2
  server.send (200, "text/html", "Relay 2 turned on.");
  digitalWrite (outputLed, 0);
}

void handleRoot() {
  digitalWrite ( led, 1 );

  char temp[400];
  int sec = millis() / 1000;
  int min = sec / 60;
  int hr = min / 60;
  int h = dht.readHumidity();
  int t = dht.readTemperature();
  snprintf ( temp, 400,

             "<html>\
  <head>\
    <meta http-equiv='refresh' content='5'/>\
    <title>NodeMCU hooked to Relay Board</title>\
    <style>\
      body { background-color: #cccccc; font-family: Arial, Helvetica, Sans-Serif; Color: #000088; }\
    </style>\
  </head>\
  <body>\
  <h1>Hello from NodeMCU!</h1>\
    <p>Uptime: %02d:%02d:%02d</p>\
  </body>\
</html>",

          hr, min % 60, sec % 60
           );
  server.send ( 200, "text/html", temp );
  digitalWrite ( led, 0 );
}

void handleNotFound() {
  digitalWrite ( led, 1 );
  String message = "File Not Found\n\n";
  message += "URI: ";
  message += server.uri();
  message += "\nMethod: ";
  message += ( server.method() == HTTP_GET ) ? "GET" : "POST";
  message += "\nArguments: ";
  message += server.args();
  message += "\n";

  for ( uint8_t i = 0; i < server.args(); i++ ) {
    message += " " + server.argName ( i ) + ": " + server.arg ( i ) + "\n";
  }

  server.send ( 404, "text/plain", message );
  digitalWrite ( led, 0 );
}

void setup ( void ) {
  pinMode ( led, OUTPUT );
  pinMode(10, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(outputLed, OUTPUT);
  digitalWrite ( led, 0 );
  Serial.begin ( 9600 );
  WiFi.begin ( ssid, password );
  Serial.println ( "" );

  // Wait for connection
  while ( WiFi.status() != WL_CONNECTED ) {
    delay ( 500 );
    Serial.print ( "." );
  }

  Serial.println ( "" );
  Serial.print ( "Connected to " );
  Serial.println ( ssid );
  Serial.print ( "IP address: " );
  Serial.println ( WiFi.localIP() );

  if ( MDNS.begin ( "esp8266" ) ) {
    Serial.println ( "MDNS responder started" );
  }

  server.on ( "/", handleRoot );

  server.on ( "/inline", []() {
    server.send ( 200, "text/plain", "this works as well" );
  } );

  server.on("/relay1", turnOnRelayOne);
  server.on("/relay2", turnOnRelayTwo);
  server.onNotFound ( handleNotFound );
  server.begin();
  Serial.println ( "HTTP server started" );
}

void loop (void) {
  server.handleClient();
}

When I execute the URL: 192.168.1.8/relay1 the outputLed blinks as per the logic in turnOnRelayOne.

But neither of the relays turns on. Please help.

score 8 · Accepted Answer · answered Mar 27 '17 at 08:24

I have several of these modules. They have an optional opto-isolator built-in, but you have to remove the jumper to use it.

Connect your GPIO trigger as you have it
Run the relay's Vcc and Gnd pins to the MCU, not the power plug.
connect the power plug's +5v to the left-most pin, where the jumper once stood: JDVcc
connect the power plug ground to the MCU or the open common Gnd on the left-group of pins.

Now your relay coil(s) will be powered by the 5v plug, but the relay's logic and control are handled by the MCU.

score 3 · Answer 2 · answered Mar 26 '17 at 15:21

The relay has no reference for what the voltage from the NodeMCU is. Since the power supplies of the two devices are isolated (from each other; the laptop may not be isolated itself, but the battery certainly should be) you can (and in fact must) connect the grounds of the relay board and the NodeMCU together. If neither power supply is isolated or if you are unsure if they are isolated then you should use an optoisolator in order to prevent potential power issues.

score 2 · Answer 3 · edited Apr 13 '17 at 12:33

2

I believe the problem could be that the relay is 5v but the signal coming from the NodeMCU is 3.3v. You may need do something like boost the signal to 5v or implement a logic level shifter, for example.

Here's a related post: https://electronics.stackexchange.com/questions/213051/how-do-i-use-a-5v-relay-with-a-3-3v-arduino-pro-mini

edited Apr 13 '17 at 12:33

Community

1

answered Mar 26 '17 at 16:42

Mazaryk

1,149
6
16

score 0 · Answer 4 · answered Jan 01 '18 at 22:31

How are you powering your ESP-12E? This is not included in your diagram. I have had success using the VU pin (5V output) when powering from the Micro-USB. You would then connect VCC to VU, GND to GND, and Signal to your GPIO4. If you are powering your ESP-12E from a 5v power supply directly into the VIN pin, then I would power the Relay from the same 5V power supply. you would connect the + from the power supply to VIN (ESP) and VCC (relay) all the grounds tied together then the GPIO4 to Signal.

score -1 · Answer 5 · answered Mar 26 '17 at 18:52

This relay module works differently. It is on when the signal is LOW and it turns off when the signal is HIGH (3v3V on the NodeMCU) So you only need to modify the code in the two functions to be LOW instead of HIGH Also make sure the NodeMCU and the relay module have a common ground.

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

const char* ssid = "said.";
const char* password = "secret";
ESP8266WebServer server ( 80 );
const int led = 13;
const int outputLed = 12;

void turnOnRelayOne(){
  digitalWrite (outputLed, 1);
  digitalWrite (5, LOW); //GPIO 5 // Relay 1
  server.send (200, "text/html", "Relay 1 turned on.");
  digitalWrite (outputLed, 0);
}

void turnOnRelayTwo(){
  digitalWrite (outputLed, 1);
  digitalWrite (4, LOW); //GPIO 4 // Relay 2
  server.send (200, "text/html", "Relay 2 turned on.");
  digitalWrite (outputLed, 0);
}

void handleRoot() {
  digitalWrite ( led, 1 );

  char temp[400];
  int sec = millis() / 1000;
  int min = sec / 60;
  int hr = min / 60;
  int h = dht.readHumidity();
  int t = dht.readTemperature();
  snprintf ( temp, 400,

             "<html>\
  <head>\
    <meta http-equiv='refresh' content='5'/>\
    <title>NodeMCU hooked to Relay Board</title>\
    <style>\
      body { background-color: #cccccc; font-family: Arial, Helvetica, Sans-Serif; Color: #000088; }\
    </style>\
  </head>\
  <body>\
  <h1>Hello from NodeMCU!</h1>\
    <p>Uptime: %02d:%02d:%02d</p>\
  </body>\
</html>",

          hr, min % 60, sec % 60
           );
  server.send ( 200, "text/html", temp );
  digitalWrite ( led, 0 );
}

void handleNotFound() {
  digitalWrite ( led, 1 );
  String message = "File Not Found\n\n";
  message += "URI: ";
  message += server.uri();
  message += "\nMethod: ";
  message += ( server.method() == HTTP_GET ) ? "GET" : "POST";
  message += "\nArguments: ";
  message += server.args();
  message += "\n";

  for ( uint8_t i = 0; i < server.args(); i++ ) {
    message += " " + server.argName ( i ) + ": " + server.arg ( i ) + "\n";
  }

  server.send ( 404, "text/plain", message );
  digitalWrite ( led, 0 );
}

void setup ( void ) {
  pinMode ( led, OUTPUT );
  pinMode(10, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(outputLed, OUTPUT);
  digitalWrite ( led, 0 );
  Serial.begin ( 9600 );
  WiFi.begin ( ssid, password );
  Serial.println ( "" );

  // Wait for connection
  while ( WiFi.status() != WL_CONNECTED ) {
    delay ( 500 );
    Serial.print ( "." );
  }

  Serial.println ( "" );
  Serial.print ( "Connected to " );
  Serial.println ( ssid );
  Serial.print ( "IP address: " );
  Serial.println ( WiFi.localIP() );

  if ( MDNS.begin ( "esp8266" ) ) {
    Serial.println ( "MDNS responder started" );
  }

  server.on ( "/", handleRoot );

  server.on ( "/inline", []() {
    server.send ( 200, "text/plain", "this works as well" );
  } );

  server.on("/relay1", turnOnRelayOne);
  server.on("/relay2", turnOnRelayTwo);
  server.onNotFound ( handleNotFound );
  server.begin();
  Serial.println ( "HTTP server started" );
}

void loop (void) {
  server.handleClient();
}

How to make a 5-volt relay work with NodeMCU?

5 Answers5

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