Design Your Circuit. Part II – CD 4060 Timer

IC 4060 is an excellent integrated circuit for timing applications. Its ten active high outputs can give time delay from few seconds to hours. With a few components, it is easy to construct a simple but reliable time delay circuit. Let us see its complete working details.

IC 4060 is an Oscillator cum Binary counter cum Frequency divider. Its inbuilt oscillator is based on three Inverters. The basic frequency of the internal oscillator is determined by the value of the timing capacitor connected to its pin 9 and that of the timing resistor in its pin 10.

Pin 11 is the Osc In ( Clock In ) to which pulses from an external oscillator such as Crystal oscillator can be given.

Each output goes high in the negative transition after the completion of one timing cycle. To get maximum time period, output Q11 is omitted in the IC itself so that double time is available between Q10 and Q12. Outputs Q1-Q3 is also absent and the output starts from Q4.

Inside the IC there is an oscillator and 14 series connected Bistables (Ripple cascade arrangement). Internally the oscillator signal is applied to the first bistable which drives the second bistable and so on. Since each bistable divides its input signal by two, a total of fifteen signals are available, each of half the frequency of the previous one. Ten of these fifteen signals are available on the output pins Q4- Q14.

HEF 4060 is CMOS version which can operate at 3 volts while CD 4060 is high voltage type that can operate between 5 to 20 volts. It is necessary to add a capacitor close to pin 16 of IC so that minute voltage changes will not affect the timing cycle. Reset pin 12 resets the timing cycle once it is grounded.

Outputs can give almost full supply voltage to drive light loads but output current is around 10 mA. Heavy loads such as relay can be operated through a driver transistor. When the high output is connected to the pin 11(clock input) through a diode, oscillation stops and IC remains latched in the high state till it resets.

Timing cycle calculation

Time t = 2 n / f osc = Seconds

n is the selected Q output number

f osc = 1 / 2.5 (R1XC1) = in Hertz

R1 is the resistance at Pin 10 in Ohms and C1, the capacitor at Pin 9 in Farads.

For example if R1 is 1M and C1 0.22 the basic frequency f osc is

1 / 2.5(1,000,000 x 0.000,000 22) = 1.8 Hz

A ready reckoner for selecting the output to get a required time delay is given below.

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