THIS IS FOR A SIMPLE DIGITAL CLOCK WITH SECONDS AND ALARM TIME DISPLAY
Typical digital clocks using clock chips MM5387/MM5402 and MM5369 show normal time in only
hours and minutes, and seconds or alarm time is visible only after pressing a pusht o on switch. Here’s a digital clock using the same IC (MM5387) that shows normal time in hours, minutes, and seconds and alarm time simultaneously. For this, ten 7-segment LED displays and a few extra ICs and some discrete components are needed.
PARTS LIST
Semiconductors:
IC1, IC5 - CD4017BE decade counter/
divider
IC2 - NE555 timer
IC3 - MM5387 clock chip
IC4 - CD4060 14-stage binary
counter
T1-T5 - BC547 npn transistor
D1-D6 - 1N4001 rectifier diode
D7, D8 - 1N4148 fast switching diode
Resistors (all ¼-watt, ±5% carbon,
unless stated otherwise):
R1 - 10-kilo-ohm
R2 - 150-ohm
R3-R7 - 15-kilo-ohm
R8 - 3.3-mega-ohm
Capacitors:
C1 - 0 .01μF ceramic disk
C2 - 4.7μF, 16V electrolytic
C3 - 1000μF, 16V electrolytic
C4 - 470μF, 16V electrolytic
C5-C7 - 0.22μF ceramic disk
C8, C9 - 47pF ceramic disk
Miscellaneous:
XTAL - 4.9152MHz crystal
LED1, LED2 - 5mm dia. red LED
DIS1-DIS10 - LT543 common-cathode
7-segment display
S1 - SPDT switch
S2-S7 - Push-to-on tactile switch
X - 230V AC primary to 4.5V-0-
4.5V secondary, 500mA
transformer
- 9V PP3 battery
Schematics
