Building a 1 second delay timer using IC-555

A one second delay timer

IC 555 timer (available in 8 pin DIP or TO-99 package) is one of the most popular and versatile sequential logic devices which can be used in mono-stable and stable modes. The inputs and output are directly compatible with both TTL and CMOS logic circuits. The functional block diagram of 555 timer is shown below in Fig 1

Fig 1

Functional Block Diagram

It has two comparators which receive their reference voltages by a set of three resistances connected between the supply voltage VCC and ground. The reference voltage for comparator 1 is 2VCC/3 and for comparator 2 is VCC/3. These reference voltages have control over the timing which can be varied electronically, if required, by applying a voltage to the control voltage input terminal. If this is not required, then a bypass capacitor (0.01microFarad) should be connected between this terminal and ground to bypass noise and/or ripple voltages from the power supply.

555 can be configured as Astable multivibrator or Monostable multivibrator. In the following demonstration, it is configured as Astable (a free running oscillator) that showcases a 1 second delay timer. It can be essentially used as 1 second delay flip-flop or trigger to some event. To configure specific time delay, there is a equation of 555 timer IC and its as follows:

T1 = 0.683*(R1+R2)*C ---- THE ON TIME

T2 = 0.693*R2------------ THE OFF TIME

In my circuit, R1 = R2 = 2200 ohms and C = 10 microFarad, thus we have T1 = 0.6seconds and T2 = 0.3seconds. 

Total time = T = T1 + T2 = 0.9seconds almost 1second delay

Here is Fig 2 which shows the circuit diagram, the popular Astable Multivibrator

Fig 2

Here is the Video which shows the 1 second timer.