The circuit 1/86400 Hz frequency generator provides one clock pulse every 24 hours from a 1 Hz input clock pulse source, which is commonly available through a digital clock. It can be used to provide am/pm indication in those digital clocks which do not have this facility, or it may be utilized to advance the date of an electronic calendar every day. It can also be used to trigger an alarm at a determined time without fail.
Circuit Description of 1/86400 Hz Frequency Generator
The present circuit 1/86400 Hz frequency generator divides the number of incoming clock pulses by a preset value using a binary counter. There are some clocks that do not involve the use of 50Hz or 60Hz pulse. In such a case, the circuit has to be made to work on the battery and not on the main supply. The input pulses to IC1 are given by the ‘seconds’ display of the digital clock, thus providing a 1 Hz pulse to the input of IC1.
The output of IC1is connected to the input of IC2 for a net division of 86400,i.e. providing a single pulse a day (every 24 hours) at the output of IC2. AND gates are used to reset binary counters after a preset number of clock pulses that have been counted by them. IC2 (CD4040) is a 12-stage binary counter and IC1 (CD4020) is a 14-stage binary counter. IC3 (CD4082) is a dual, four-input AND gate.
Due to the low power consumption and wide operating voltage (5V-12V) of CMOS ICs used, the circuit can be fitted in a table-top or a digital wall clock.
PARTS LIST OF 1/86400 HZ FREQUENCY GENERATOR
|
Resistor (all ¼-watt, ± 5% Carbon) |
|
R1, R2 = 100 KΩ |
|
Semiconductors |
|
IC1 = CD4020 (14-stage binary counter) IC2 = CD4040 (12-stage binary counter) IC3 = CD4082 (Dual, four input AND gates) D1, D2 = 1N4148 (silicon switching signal diode) |
|
Miscellaneous |
|
SW1 = Push-To-On switch |