Astable Multivibrator Using 555
Category: 555 Timer IC
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is designed and simulated in Proteus 7.10. In this circuit you will learn about the famous timer ic which is NE555. Many companies make this IC and there prefix can be changed but number will be 555, for example Texas Instruments make this IC with name LM555. Functionality will be same of both the IC's. So manufacturer doesn't matter unless the functionality is same. The 555 timer IC can be used in all multivibrator mode. It can be used as a) Astable multivibrator b) Monostable multivibrator c) Bistable multivibrator In this circuit 555 timer IC is used as Astable multivibrator mode. The further two modes will be added in next circuits. Come back daily to get new circuit. The working of this circuit is given below. 1. Astable mode means there will be no stable levels at the output. Which means the output level will be fluctuating between high and low level. 2. The operating range of 555 timer IC is +5Vdc to 18Vdc. 3. An RC time (product of C2 and R1) is used to make the output for certain period of time. 4. The trigger pin is active low (1/3 of Vcc) and it will trigger the output at low or negative pulse. 5. In this circuit the trigger pin (TR) is connected with the threshold (TH) pin. The threshold pin determines when to reset the internal flip flop timer. 6. The pin 5 (CV) is the control pin, it is not used. Therefore it should grounded via 10nF capacitor. 7. The pin 4 is reset (R). It should be connected with Vcc. 8. Initially the trigger pin receives trigger pulse through C2, and it will receives continuous pulses through RC (R2*C1) oscillator. So, the output will trigger at each trigger pulse. Application: 1. This circuit can be used to make the square pulses. 2. This circuit can be used to make the clock pulses. Download these files for performing more experiments.