Right PIN to activate a wireless relay with ESP8266 ESP-01

Question

I'm trying to program an ESP8266 ESP-01 module to let it connect to my personal wifi network and activate a wireless relay that I've bought.

No problems with Wifi connection so I've omitted the code about it, my problem is to find what is the right PIN to set to LOW/HIGH to control my relay. Setting relayPin to 1 as shown in this code works and with it I can see the embedded LED turning on and off.

const int relayPin = 1;

void setup() {
    pinMode(relayPin, OUTPUT);
}

void loop() {
    Serial.println("Close Relay for 100 ms and then Open");
    digitalWrite(relayPin, LOW);
    delay(100);
    digitalWrite(relayPin, HIGH);
    delay(200);
}

Surfing the web I've found the following diagram about the ESP8266 ESP-01 module:

I've tried to set relayPin to 0 or to 2 but the relay doesn't activate/deactivate.

So, what is the right PIN number to set in my relayPin constant to control the GPIO0 port?

The relay works succesfully if I give him +3.3V on GPIO0 with an external power.

Thanks in advance

Answer 1

most GPIO pins on the ESP8266 "boot" up in INPUT mode

You'll need to

const int relayPin = 0; // or 2

void setup() 
{
    pinMode(relayPin, OUTPUT);
}

The reason GPIO1 works is because GPIO1 is serial TxD - so, it's set to output

Answer 2

Looking at better pictures of the PCB on ALIExpress it looks like GPIO0 is used to switch the relay.

What that pin maps to, though, depends on what board you have selected in the IDE.

Answer 3

1 solution I did is to use rx [GPIO 3] to drive relay. For this,

1. Need to short the GPIO 0 and GPIO 3(Rx) pin on the relay board.
2. While inserting the ESP-01, either bend the GPIO 0 or completely remove it from ESP-01 board. Be careful, on removing you wil find difficult to program the ESP-01 module again because GPIO 0 should go low at boot time to enable program mode. And this is the reason why GPIO 0 is HIGH on boot.

If you want, you can try this product Smart Switch. Android Based ESP01 Relay Module

Answer 4

I had this exact same problem. Solution was to put 5 volts on the relay. There is a regulator on the wireless relay that gives 3v to the ESP-01 and not 5v. But 5v is required for the relay to work.

Answer 5

You can use any pin of the esp-01 You may want to tell the TX and Rx pins though to behave like regular I/O with the pinMode/Function_3 command as described here:

https://arduinodiy.wordpress.com/2018/06/14/simple-wifi-relay-board-or-diy-sonoff-sv-sonoff-4-channel-2/