Introduction: Bar-graph Display Digital Clock
CD4017 is a versatile integrated circuit (and its small brother CD4022) and has infinite applications. This digital clock project is made from 8CD4017´s plus a 7812 or 78L12 for supply. Time reference is obtained from the AC line frequency(50-60Hz)and subdivided by the CD4017´s to obtain seconds, minutes and hours. AC line frequency is quite stable and has been used by electric wall clocks for decades. The 4017´s drive LED bar-graph displays directly from its outputs with 1 single current limiting resistor. A microcontroller version of this project would be much simpler to wire... but this is also great fun!
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Step 1: Project Overview
Step 2: Circuit Diagram (part 1) & Main Components
IC1: 7812 or 78L12 voltage regulator IC
IC2-IC5: CD4017 cmos decade counter
T1: 12v+12v secondary power transformer. (current requirement is very low)
Step 3: IC2: 50-60Hz to 10 Hz Divider
Step 4: IC2 Line Frequency Selection
connect reset source signal according to your local line frequency
Step 5: IC3: 10Hz in to 1 Hz Out (divide by 10)
Step 6: IC4-IC5: 1Hz in to 1cycle Per Minute Out (divide by 60)
Step 7: Circuit Diagram (part 2) Display
IC6-IC9: CD4017 cmos decade counter
Display: 4x 10 led bar-graph display
SW1-SW2 push-button momentary switch (time set)
Step 8: IC9: Minutes Units (0-9)
Step 9: IC8: Minutes Tens (0-5)
Step 10: IC7: Hours Units (0-9)
Step 11: IC6: Hours Tens (0-2)
Step 12: And Gate Decodes "24" and Resets IC6-IC7 to 0
Step 13: Seconds LED
Led LD1 blinks every second. Use SW1-SW2 to set time.