SSD1306 + DS3231 Desk Clock

A standalone 24-hour desk clock using the SSD1306 OLED driver and a DS3231 RTC — no Wi-Fi, no internet, just the textbook display + timekeeping pair.

Difficulty: Breadboard. Estimated build time: about 45 minutes. Estimated parts cost: about US$9.50. 4-part bill of materials with live supplier pricing. A through-hole clock that keeps accurate time even when you unplug it.