Why Capacitor is must use in all Timing Circuits?

Almost all electronic timing circuits use a capacitor as a main component especially all analog timing circuits use capacitors for their operations. Digital timing circuits can be made without capacitors because they use flip flop circuits, crystal oscillators but analog timing cannot be possible to make without capacitors. So, today we are going to know why the capacitor is must use in all timing circuits or the role of a capacitor in a timing circuit.

Actually, the concept is very simple. The whole phenomenon depends upon the basic characteristic of a capacitor which is charging and discharging. Yes, the charging and discharging property of the capacitor is used in all timing circuits.

We know that a capacitor takes some time to get fully charged and to fully discharge. This property we can use for the timing circuit. If we control the charging and discharging time of the capacitor, it can act as a timing circuit.

Let's understand with an example.

Here, you can see in the below figure a timer switch circuit is given below.

Here, you can see the R1, C1, R2 are connected in such a way that they can provide a forward voltage to the base of the transistor. When a forward voltage will be applied to the base of the transistor, it will start to conduct current and the LED will glow.

Here, the whole timing mechanism depends upon the charging and discharging of the capacitor C1.

When the switch S1 is pressed the 12V DC supply will be applied across the capacitor and it starts charging. After fully charged, the capacitor will start discharging through the base terminal of the transistor. Hence the transistor will be turned on.

After full discharging, again the capacitor will start charging and this mechanism will repeat.

We can control the charging and discharging of the capacitor by varying the value of the potentiometer P1 and we can change the time delay.

Now, you may understand how we use the charging and discharging property of a capacitor in electronic timing circuits. It is very easy and simple.

As the capacitor is the main part of the timing circuit, you may see a capacitor is always used with the IC 555 Timer circuit also.

Read Also: 

            1. Why Ceramic Capacitors mostly used in Electronic Circuit than others?
            2. Why Capacitor need to use with IC 78XX Series Voltage Regulators?
            3. Difference between Coupling Capacitor and Bypass Capacitor

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