Components

	ESP32-WROOM-32D Espressif Systems	x 1
	G6K-2F-Y3VDC OMRON	x 1
	Mini Breadboard	x 1
	269 JKL Components Corp.	x 1

Description

Esp32 Home Automation

There are relay modules whose electromagnet can be powered by 5V and with 3.3V. Both can be used with the ESP32 or ESP8266 – you can either use the VIN pin (that provides 5V) or the 3.3V pin.

Additionally, some come with built-in optocoupler that add an extra “layer” of protection, optically isolating the ESP boards from the relay circuit.

The second set of pins consists of GND, VCC, and JD-VCC pins. The JD-VCC pin powers the electromagnet of the relay. Notice that the module has a jumper cap connecting the VCC and JD-VCC pins; the one shown here is yellow, but yours may be a different color.

With the jumper cap on, the VCC and JD-VCC pins are connected. That means the relay electromagnet is directly powered from the ESP power pin, so the relay module and the ESP circuits are not physically isolated from each other.

Without the jumper cap, you need to provide an independent power source to power up the relay’s electromagnet through the JD-VCC pin. That configuration physically isolates the relays from the ESP with the module’s built-in optocoupler, which prevents damage to the ESP in case of electrical spikes.

Controlling a Relay Module – MicroPython Code (Script)

The code to control a relay with the ESP32 or ESP8266 is as simple as controlling an LED or any other output. In this example, as we’re using a normally open configuration, we need to send a LOW signal to let the current flow, and a HIGH signal to stop the current flow.

boot.py script

def web_page():

if relay.value() == 1:

relay_state = ''

else:

relay_state = 'checked'

html = """<html><head><meta name="viewport" content="width=device-width, initial-scale=1"><style>

body{font-family:Arial; text-align: center; margin: 0px auto; padding-top:30px;}

.switch{position:relative;display:inline-block;width:120px;height:68px}.switch input{display:none}

.slider{position:absolute;top:0;left:0;right:0;bottom:0;background-color:#ccc;border-radius:34px}

.slider:before{position:absolute;content:"";height:52px;width:52px;left:8px;bottom:8px;background-color:#fff;-webkit-transition:.4s;transition:.4s;border-radius:68px}

input:checked+.slider{background-color:#2196F3}

input:checked+.slider:before{-webkit-transform:translateX(52px);-ms-transform:translateX(52px);transform:translateX(52px)}

</style><script>function toggleCheckbox(element) { var xhr = new XMLHttpRequest(); if(element.checked){ xhr.open("GET", "/?relay=on", true); }

else { xhr.open("GET", "/?relay=off", true); } xhr.send(); }</script></head><body>

<h1>ESP Relay Web Server</h1><label class="switch"><input type="checkbox" onchange="toggleCheckbox(this)" %s><span class="slider">

</span></label></body></html>""" % (relay_state)

return html

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.bind(('', 80))

s.listen(5)

while True:

try:

if gc.mem_free() < 102000:

gc.collect()

conn, addr = s.accept()

conn.settimeout(3.0)

print('Got a connection from %s' % str(addr))

request = conn.recv(1024)

conn.settimeout(None)

request = str(request)

print('Content = %s' % request)

relay_on = request.find('/?relay=on')

relay_off = request.find('/?relay=off')

if relay_on == 6:

print('RELAY ON')

relay.value(0)

if relay_off == 6:

print('RELAY OFF')

relay.value(1)

response = web_page()

conn.send('HTTP/1.1 200 OK\n')

conn.send('Content-Type: text/html\n')

conn.send('Connection: close\n\n')

conn.sendall(response)

conn.close()

except OSError as e:

conn.close()

print('Connection closed')

After making the necessary changes, upload the boot.py and main.py files to your board. Press the EN/RST button and in the Shell you should get the ESP IP address.

Then, open a browser in your local network and type the ESP IP address to get access to the web server.

You should get a web page with a toggle button that allows you to control your relay remotely using your smartphone or your computer.

Insert your network credentials in the following variables:

ssid = 'REPLACE_WITH_YOUR_SSID'

password = 'REPLACE_WITH_YOUR_PASSWORD'

Uncomment one of the following lines accordingly to the board you’re using. By default, it’s set to use the ESP32 GPIO.

# ESP32 GPIO 26

relay = Pin(26, Pin.OUT)

# ESP8266 GPIO 5

#relay = Pin(5, Pin.OUT)

Code

python script_

MicroPython

def web_page():
  if relay.value() == 1:
    relay_state = ''
  else:
    relay_state = 'checked'
  html = """<html><head><meta name="viewport" content="width=device-width, initial-scale=1"><style>
  body{font-family:Arial; text-align: center; margin: 0px auto; padding-top:30px;}
  .switch{position:relative;display:inline-block;width:120px;height:68px}.switch input{display:none}
  .slider{position:absolute;top:0;left:0;right:0;bottom:0;background-color:#ccc;border-radius:34px}
  .slider:before{position:absolute;content:"";height:52px;width:52px;left:8px;bottom:8px;background-color:#fff;-webkit-transition:.4s;transition:.4s;border-radius:68px}
  input:checked+.slider{background-color:#2196F3}
  input:checked+.slider:before{-webkit-transform:translateX(52px);-ms-transform:translateX(52px);transform:translateX(52px)}
  </style><script>function toggleCheckbox(element) { var xhr = new XMLHttpRequest(); if(element.checked){ xhr.open("GET", "/?relay=on", true); }
  else { xhr.open("GET", "/?relay=off", true); } xhr.send(); }</script></head><body>
  <h1>ESP Relay Web Server</h1><label class="switch"><input type="checkbox" onchange="toggleCheckbox(this)" %s><span class="slider">
  </span></label></body></html>""" % (relay_state)
  return html

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('', 80))
s.listen(5)

while True:
  try:
    if gc.mem_free() < 102000:
      gc.collect()
    conn, addr = s.accept()
    conn.settimeout(3.0)
    print('Got a connection from %s' % str(addr))
    request = conn.recv(1024)
    conn.settimeout(None)
    request = str(request)
    print('Content = %s' % request)
    relay_on = request.find('/?relay=on')
    relay_off = request.find('/?relay=off')
    if relay_on == 6:
      print('RELAY ON')
      relay.value(0)
    if relay_off == 6:
      print('RELAY OFF')
      relay.value(1)
    response = web_page()
    conn.send('HTTP/1.1 200 OK\n')
    conn.send('Content-Type: text/html\n')
    conn.send('Connection: close\n\n')
    conn.sendall(response)
    conn.close()
  except OSError as e:
    conn.close()
    print('Connection closed')

Schematic and Layout

circuit

Web-Server-control-a-Relay-module-with-ESP32.jpg