pwm modulator and demodulator

[soni sharma]

hi,i want to make pwm modulator and demodulator circuit...........i have made squre wave carrier signal of 1.5 khz using 555 timer....but the problem is that i have confusem in circuit components value of pwm modulator and demodulator....regarding 1.5 khz carrier signal and 9 volt supply what will be the value of Ra in modulator (monostable multivibrator with modulating input 2 volt ) circuit,and low pass filter components for demodulator?????????
plz help.

 

[MikeMl]

What will carry the PWM signal from modulator to demodulator? RF, Light, a twisted pair?

 

[soni sharma]

RF signal

 

[MikeMl]

What is the bandwidth of the receiver? The 555 makes fast rise/fall times. Depending on the bandwidth of the receiver, you may have to do serious low-pass filtering on the PWM signal before using it to modulate a transmitter. This will constrain the bandwidth of the transmitted signal to prevent interference with adjacent channels, as well as keeping the signal within the bandpass of the receiver.

 

[jpanhalt]

Transmitting PWM by RF as I think you may be trying to do will be problematic, because the pulse width of the received signal will not be exactly the same as the pulse width of the transmitted signal. The pulse width is error is particularly bad at the beginning of the data stream.

Here is a discussion of coding techniques: file:///D:/eProjectBAK081208/Microcontroller/Tutorials/Manchester%20Encoding/Data%20Encoding%20Techniques.htm

You may want to search on "Manchester coding" separately.

John

 

[muugii]

hi. i want to generate different hertz signals using a PWM. please help!!! CCS C

 

[alec_t]

Muugii, you've hijacked someone else's thread. Start your own.