Good day
We are designing an audio system capable of sending audio through a transmitter using Frequency modulation and receiving it at a
min of 1.5m away. We where instructed to choose between white,red or infra red LEDs. We had to keep in mind the wavelength of the audio signal to be transmitted (between 10kHz and 50kHz) also the sensitivity to the different types of LEDs that the phototransitor will pick up.But this week we have to design our LED transmision circuit and phototransistor receiver circuit and we have to choose our carrier frequency(32.768/40/75/77.5 kHz) by doing a simple experiment. We are instructed as follows :
1)How will you drive the LED? 2) Will the circuit work both in daylight and in complete darkness? 3)How will you maximise the range? 4) Based on your carrier frequency and bandwidth calculations in part 1 above, how important are the rise and fall times of the phototransistor? Can you do something to improve them? 5) Determine the required currents and voltages to get the components into their desired operating regions.
We really would like to have some insight to these questions before we submit our own report, to check if we go about this the rigth way.
Greetings
We are designing an audio system capable of sending audio through a transmitter using Frequency modulation and receiving it at a
min of 1.5m away. We where instructed to choose between white,red or infra red LEDs. We had to keep in mind the wavelength of the audio signal to be transmitted (between 10kHz and 50kHz) also the sensitivity to the different types of LEDs that the phototransitor will pick up.But this week we have to design our LED transmision circuit and phototransistor receiver circuit and we have to choose our carrier frequency(32.768/40/75/77.5 kHz) by doing a simple experiment. We are instructed as follows :
1)How will you drive the LED? 2) Will the circuit work both in daylight and in complete darkness? 3)How will you maximise the range? 4) Based on your carrier frequency and bandwidth calculations in part 1 above, how important are the rise and fall times of the phototransistor? Can you do something to improve them? 5) Determine the required currents and voltages to get the components into their desired operating regions.
We really would like to have some insight to these questions before we submit our own report, to check if we go about this the rigth way.
Greetings