serge_saati

Hello, the advantage is the wireless anand the limitation is the distance range.

The infrared diode is not biased. When no infrared signal come on it, the voltage at the input of the filter is 5V. When infrared signal come on it, the voltage at the input of the filter is -5V. When the infrared signal oscillates, because the data transmission is an oscillating signal (up to 100 MHz), the voltage at the input of the filter oscillates between -5V to 5V. So there is an alternating current (peak voltage is 5V). The filter is used to let pass the good frequency. The digital amplifier is used to smooth the signal. It's mean to convert analog signal (caused by the limited response time of the infrared diode) into direct current digital signal. The network card receive this signal. We can't use CMOS gates because they are too slow. The TTL logic gates of the series AS (74ASxx) have short response time (less than 1.7 ns) so thy can response to frequency higher than 200 MHz. The 9 volt battery of the first circuit is only used to convert direct current into alternating current. The 5V source is used to supply all of the digital components and works with the 9V battery to produce the alternating current. Because the ground of the power supply is alway connected to the ground of the logic gate, the gate can receive the negative polarity of the 9V battery if its positive polarity is connected to the positive supply of the 5V source.

The batteries are used to convert the infrared signal into electric signal. Of course, the electric signal is alternative. The filter lets pass only the good frequency. But it has other ways to do that. We can use only the voltage source of the computer's power supply. We have to use the red wire (+5V) and the black wire (GND). But we must add to other logic gates. Those must be of series 74AS and type TTL. Remember, all the logic gates of the circuit must be powered with the 5V power supply of the computer. So the +5V must be connected to the Vcc pin and the ground must be connected to the GND pin. I send you the new schematic circuit possible for the receptor of the desktop computer.