Fm Using 555. Here is a frequency modulation fm circuit that uses a 555 timer in astable mode to generate a sine wave carrier. Since the output of a wien bridge oscillator is a pure sine wave having both the positive and negative half cycles they should not be directly applied to the 555 which works on positive dc voltage only.
Since the frequency is near 540 khz sweep the radio and the right pot audio ground. In 1972 signetics corporation first introduced this device as the se ne 555. The sine wave generated using the wien bridge oscillator applied to the pin number 5 of the 555 timer ic to modulate the frequency of the generated pulses.
Fm generation using 555 timer circuit diagram.
Here is a frequency modulation fm circuit that uses a 555 timer in astable mode to generate a sine wave carrier. This 555 timer circuit can generate fm square waves as a dc biased vco or astable but only from 3 3khz to 4 4khz using the ctrl input 0 to 9vdc. The sine wave generated using the wien bridge oscillator applied to the pin number 5 of the 555 timer ic to modulate the frequency of the generated pulses. Once you hear it your done but the radio has to be a little loud because there is no pre amp on the transmitter.
