Contributors

Requirements

• ESP32 38P Pins
• DS3231 RTC Module + CR2032 battery (offline recommend)
• 5v 1-16 Channel Relay
• Female to Female Dupont Wire
• 5v 2-5a Power supply

Optional

• 5v UPS (Maintain RTC Time without DS3231 or NTP)
• Solid State Relay (SSR DC-AC) (High Load Setup)
• ESP32 Expansion Board
• Stable Wifi Connection for NTP/RTC sync (online if no ds3231)

Arduino Libraries

• ArduinoJson
• RTClib v1.14.1

Installation

Download and install

ESP32 Win/Linux Drivers

• CH340G: https://sparks.gogo.co.nz/ch340.html
• CP2102: https://www.silabs.com/software-and-tools/usb-to-uart-bridge-vcp-drivers?tab=downloads
• FT232: https://ftdichip.com/wp-content/uploads/2025/03/CDM-v2.12.36.20-Universal-Driver-for-x64-WHQL-Certified.zip

Flasher

Android (otg)

• https://play.google.com/store/apps/details?id=io.serialflow.espflash

Android Termux

• https://github.com/7wp81x/Termux-ESP-Flasher

Windows

• https://dl.espressif.com/public/flash_download_tool.zip

Linux

esptool --port <PORT> write_flash 0x0 esp32-dump-0x0.bin

Win/Linux Browser

• https://g3gg0.github.io/esp32_flasher/flasher.html

Flash firmware

• Download the Firmware and Flash
• https://github.com/xiv3r/esp32-automatic-timer-switch/releases/tag/esp32
• Flash Offset

esp32-dump-0x0.bin: 0x0

WiFi Key

• WiFi SSID: ESP32_16CH_Timer_Switch
• Password: 12345678

Activation

• Without ds3231 or wifi the time runs from internal rtc

° Online

• Go to Wifi settings and connect to your home wifi to set the rtc time automatically

° Offline

• Go to Time settings and tap Sync Browser to set the rtc time

Relay Naming

• Double click relay name to edit

Set the Time (country)

Set to your country time e.g for PH (UTC+8.0) 28800 seconds

• Search your country gmt offsets in seconds and paste to the Time -> GMT Offset
• e.g for negative gmt: -28800
• e.g for positive gmt: 28800
• https://github.com/xiv3r/esp32-automatic-timer-switch/blob/main/gmt-offsets-seconds.md

Access

• mDNS:esp32-16ch-timer-switch.local
• Captive Portal: Auto redirect
• Gateway:192.168.4.1
• WAN:192.168.1.123
• Global:Enable Port Forwarding on your router to access anywhere

Isolate Relay Power

⚠️ Use the Main relay power input and Avoid using VCC and GND from the relay IN GPIO Pin row

5V Relay

• Remove the Yellow VCC-JDVCC jumper.
• Relay JD-VCC pin: Connect to external 5V Positive wire.
• Relay GND pin: Connect to external 5V Negative wire.
• Relay VCC pin: Connect to ESP32 5V (powers the LED).

12V Relay

• Remove the Yellow VCC-JDVCC jumper.
• Relay JD-VCC pin: Connect to external 12V Positive wire.
• Relay GND pin: Connect to external 12V Negative wire.
• Relay VCC pin: Connect to ESP32 5V (powers the LED).

Reset

• Hold BOOT button for 5 seconds to factory reset

Restart

• Press EN button to restart

16 CHANNEL RELAY GPIO Connection

2x8CH  |  ESP32 38P
VCC _____ 5V
IN8 _____ GPIO23  Relay 1
IN7 _____ GPIO32  Relay 2
IN6 _____ GPIO33  Relay 3
IN5 _____ GPIO25  Relay 4
IN4 _____ GPIO26  Relay 5
IN3 _____ GPIO27  Relay 6
IN2 _____ GPIO14  Relay 7
IN1 _____ GPIO13  Relay 8
GND _____ GND

VCC _____ 5V
IN1 _____ GPIO1   Relay 9  (TX)
IN2 _____ GPIO3   Relay 10 (RX)
IN3 _____ GPIO19  Relay 11
IN4 _____ GPIO18  Relay 12
IN5 _____ GPIO5   Relay 13
IN6 _____ GPIO4   Relay 14
IN7 _____ GPIO2   Relay 15
IN8 _____ GPIO15  Relay 16
GND _____ GND

DS3231 GPIO Connection

DS3231 |  ESP32 38P
VCC _____ 3.3V
SDA _____ 21
SCL _____ 22
GND _____ GND

Build Firmware

Auto Build firmware binaries using github action

• https://github.com/xiv3r/arduino