CMOS Pocketable Timekeeper

CMOS Pocketable Timekeeper

Here is a circuit of simple project builds into a fine CMOS based pocketable timekeeper. The main purpose of CMOS pocketable timekeeper circuit is to avoid getting late to several place i.e. office, meeting, appointment etc. An alarm from piezo buzzer is produced before minutes of selected expiry time. The timing of standard 1 and 2 – hours with 15 – minutes and 4 – hours makes this circuit versatile. Glowing of LED in every few minutes is the indication of working of circuit.

timer project

Circuit description CMOS pocketable timekeeper

The circuit CMOS pocketable timekeeper is built around two low-cost CMOS ICs (HCF4060BE and CD40106). The entire circuit pocketable timekeepercircuit is divided into four main sections, the clock base oscillator. This oscillator generates pulse for 2.2R2C2 second. The frequency driver get time period input from the output of clock base oscillator and divide the basic frequency by 210, 212, 213, 214 i.e. 1024, 4096, 8192 or 16384 in order to get time period of 15 minute, 1 hour, 2 hours and 4 hours respectively. This is followed by an AF oscillator, which built around HEX inverter IC CD40106. The first inverter (a) is configured as AF oscillator at about 2 KHz. The oscillative frequency is determined by timing component R3 and C3. The output from AF oscillator is fed to buffer section in order to boosts the output from AF oscillator. Finally, boosted output is given to ceramic piezo buzzer for alarm.

Switch SW1 is a two-pole 5 way switch as shown in figure 2. At position 1 CMOS pocketable timekeeper remains on off position where at position 2, 3, 4, and 5 it switched on to 15 minute, 1 hour, 2 hours, and 4 hours respectively.

The versatile circuit CMOS pocketable timekeeper consumes much less current because the counters are reset to zero by the power-on-reset circuit based on R2 and C2.

The time base pulses are counted by the interval counters as shown in table 1.


Position of SW1


Timing cycle duration

Free time*


4 hours

14058.1 seconds

6 minutes


2 hours

7030 seconds

3 minutes


1 hour

3515 seconds

1.5 minutes


15 minutes

879 seconds

Not significant





*Free time refers to the time before the actual time lapses and the buzzer sounds.


Resistors (all ¼-watt, ± 5% Carbon)

R1, R2, R3 = 100 KΩ

R4 = 680 Ω

VR1 = 1 MΩ


C1 = 470 nF styroflex or polyster

C2 = 100 nF ceramic disc

C3 = 5 nF ceramic disc

C4 = 220 µF/10 V electrolytic


IC1 = HCF 4060BE (oscillator and binary counter and frequency divider)

IC2 = CD40106 HEX inverter

D1 = 1N4148


PZ1 = 27mm, piezo speaker with low profile body

SW1 = Two-pole, five-way slide switch

LED1 = TiL209

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