PAGE 102 OF 150 · DISPLAYS & INDICATORS
LED Clock Display Basics
Hours and minutes are shown with four digits.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Parts of a clock display
A clock needs a time source, a display and a way to set the time.
- Time source: a real-time clock chip such as the DS3231 stays accurate to seconds per month. A bare microcontroller crystal drifts more.
- Display: four seven-segment digits, with a colon that blinks once a second.
- Controls: two buttons for hours and minutes.
Add a light sensor or dimming schedule so the clock is not dazzling in a dark bedroom. Decide between 12 and 24 hour formats early.
REMEMBER
Time accuracy comes from the clock chip, not the display.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
Explore LED clocks, stopwatches and electronics at cosycom.com.