Ic 555 timer as astable

Ic 555 timer as astable and working principle

1. IC 555 Timer as astable Multivibrator DONE BY: DOMINIC HENDRY GOKUL DINESH KUMAR DANIEL JESHTUS

2. IC Timer 555

3. 555 IC Timer Astable Multivibrator Functional Block Diagram

4. The circuit consists of: Comparator A, Comparator B, 3 Resistors of 5k ohms each Capacitor of 0.01 μ F Circuit Explanation

5. CIRCUIT

6. CONNECTOIN DIAGRAM

7. The astable multivibrator does not require any external trigger to change the state of the output. Hence the name free running oscillator. The time during which the output is either high or low is determined by the two resistors and a capacitor which are externally connected to the 555 timer. The astable multivibrator generates a square wave, the period of which is determined by the circuit external to IC 555. WORKING

8. Let t1 and t2 represent the charge and discharge times of the astable multivibrator respectively. were RA and RB are in ohms and C is in Farad. Astable Multivibrator Charge and Discharge Times

9. Astable Multivibrator Cycle Time Astable Multivibrator Duty Cycle Time The duty cycle is defined as the ratio of charge time constant (t1) to the total cycle time (T) and for the astable oscillator it is found to be:

10. The simple operation and less number of external components make the astable multivibrator using 555 IC a popular one. The perfect square wave output from the circuit makes it good for many applications. Easy to design, low cost and no external triggering are the other advantages. The disadvantage is that we cannot achieve a duty cycle less than or equal to 50% using this circuit. This problem can be solved by inverting the output or by using a diode parallel to RB. ADVANTAGES DISADVANDAGES