ESP 01 - Control 5v Relay | Micro controller | 1 Channel Relay | For beginners | Arduino IDE | Control LED (On and OFF)

Control 1-Channel relay using ESP 01

In this tutorial, we will learn about a relay and use ESP 01 to control a 5v 1-channel relay. Relay is a electromagnetic switch that can control high voltage devices with a low voltage input signal. It provides you the ability to control devices like a normal household switch by acting as a bridge between micro controller and real environment.

1-Channel relay can control one high voltage device and uses one input trigger to activate the relay. Relays can be Active HIGH/LOW triggered (If relay gets triggers on Active LOW on input signal such relays are Active LOW trigger relays and vice versa). 1 Channel relay contains 3 input pins  Vcc, GND and IN as show above. Relay has three output terminals namely NO (Normally Open), NC (Normally Closed) and COM (COMmon). When the relay is in non active state, NC and COM are in connected state and when relay is in active state NC and COM connection becomes open and NO and COM terminals are moved to connected state.

Relay can be used to either switch off a high voltage device upon relay trigger (by connecting the device between NC and COM) or to switch on a high voltage device (by connecting the device between NO and COM).

Now that we understood about relay, lets try to control it using ESP 01 as micro controller. I will be making a separate post for controlling relay using ESP and its WIFI capability. This tutorial we will purely use ESP 01 as a simple micro controller to switch on and off a led strip. 

Parts needed

1. ESP 01

2. 5v 1 channel Relay (Active Low trigger). Detailed video here.

3. Multi output voltage converter power module. (12V DC in, 3.3v and 5v out).             Detailed video here.

4. DC male and female jacks

5. 10 cm jumper wires

6. USB UART  adapter for programming ESP 01

7. LED strip.

Now Lets Code......

Place ESP-01 in slot of USB UART adapter and insert in USB slot of your device

Let me explain a bit of below code. ESP built in LED and relay will be turned on (both are active LOW triggered), wait for 5 sec, turn LED and relay off and wait for 3 secs. This continues in a loop

Compile and upload. (see this post to know how to program ESP-01)

Pasting code here for reference.

#define RELAY 0

void setup() {

  Serial.begin(115200);

  pinMode(RELAY,OUTPUT);

  digitalWrite(RELAY, HIGH);

  pinMode(LED_BUILTIN, OUTPUT);

  digitalWrite(LED_BUILTIN, HIGH); 

}

void loop() {

  Serial.println("relay ON. Waiting for 5 sec......");

  digitalWrite(LED_BUILTIN, LOW);  

  digitalWrite(RELAY,LOW);

  delay(5000);            

  Serial.println("relay OFF. Waiting for 3 sec......");

  digitalWrite(LED_BUILTIN, HIGH);  

  digitalWrite(RELAY,HIGH);

  delay(3000); 

}

Now lets get to hardware setup.

Steps to connect parts

1. Connect 3.5mm DC male connector +ve to Relay COM (red wire), Relay NO to DC-IN in power module (red wire with female jumper pin at one end), 3.5mm DC male connector -ve to GND of power module (black wire) as shown below. 

2. Now connect ESP-01 GND to power module GND (black wire) and ESP-01 3.3v to power module 3.3v (white wire) as shown below

3. Connect 3.3v from power module to Vcc of Relay (red wire) and GND of power module to GND of relay (brown wire).  

4. Now connect signal wire (yellow) from ESP-01 IO0 pin to IN of relay. 

5. Now connect both 3.5mm Male and Female connector to led strip.

Turn on the power module by connecting a 12 V adapter and the output should be similar to below video.