1. D1-Mini-esp8266-clock Esp8266 accurate digital clock using ds3231sn, a 0.96 inch Oled display,with wifi NTP time setting,ds18b20 temperature sensor. ESP8266 Digital Clock

ESP8266 Smart Clock

A clean and accurate smart clock built using an ESP8266 (Wemos D1 Mini), DS3231 RTC, DS18B20 temperature sensor, and a 128×64 OLED display. It keeps time reliably using:

• DS3231 hardware RTC
• On-demand NTP sync
• Software-based second ticking
• A smooth boot animation
• Compact and optimized OLED rendering

This project is the result of multiple iterations focused on timing accuracy, display stability, and clean code structure.

Features

• Accurate timekeeping with DS3231 SN version
• WiFi to NTP time sync on demand
• Smooth software second ticking
• Two display modes: Time and Temperature
• DS18B20 high precision temperature reading
• Four-dot smooth boot animation
• Optimized redraws to avoid flicker
• All strings moved to PROGMEM
• WiFi disabled most of the time for low power

Parts Used

• Wemos D1 Mini (ESP8266)
• DS3231 RTC module (SN version recommended)
• DS18B20 temperature sensor
• 128×64 OLED Display (I2C, SSD1306)
• Two momentary push buttons
• 4.7kΩ resistor (DS18B20 pull-up)
• Jumper wires

Wiring Overview

I2C Devices (OLED and RTC)

Both share the same bus.

• SCL → D1
• SDA → D2
• VCC → 3.3V
• GND → GND

Full Connection Table

OLED (SSD1306 I2C)

• VCC → 3.3V
• GND → GND
• SCL → D1
• SDA → D2

DS3231 RTC

• VCC → 3.3V
• GND → GND
• SCL → D1
• SDA → D2

DS18B20 Temperature Sensor

• VDD → 3.3V
• GND → GND
• DQ (Data) → D5
• 4.7kΩ resistor between DQ → 3.3V

Buttons

Mode Switch

• One side → D3
• Other side → GND

WiFi Sync Switch

• One side → D6
• Other side → GND #Power *I am using a AMS117 regualator to power all the components, I am using the onboard regulator of the d1 mini to power it.

How It Works

• On boot, a four-dot animation plays while the DS3231 is read.
• The ESP8266 starts counting from the exact second the RTC reports.
• Every 30 seconds the RTC is read again to correct small drift.
• Pressing the WiFi button enables WiFi, fetches NTP time, updates the RTC, and disables WiFi, this is useful to set time to a new
• RTC and then in future correct RTC drifts using a single button press.
• The OLED only updates when necessary using a dirty flag system.
• There is a blinking colon in between the hours and minutes like this HH:MM, this provides a nice look and also is a good * indicator if the loop is working properly.

License

This project is licensed under the MIT License.