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Posted Feb 02, 2012 at 2:53 pm
Figure 1
The circuit is aimed to provide a method for receiving serial data on one pin and transmitting serial data on another with a modulation at the infrared detectors band pass frequency.
A tiny 8-pin PIC12F508 microcontroller is the brain of the Air-Byte transceiver where the PIC monitors the GPIO connected to the PC serial port TX Pin 3 and generates the 40 kHz IR carrier when Pin 3 transitions from logic low to logic high. The carrier is being suppressed during low periods.
The data output of IR detectors is being inverted using the 2N3906 PNP transistor. The serial port RX pin of PC should be idle low when serial data is not being received during idle periods. The PNP transistor is necessary since the idle output logic of IR detector is logic 1. The PNP inverter circuit can be neglected if a MAX232 RS232 to TTL level convert IC is used where the IR module data output can be connected directly to MAX232.
The current is being limited by adding 10K resistor in series with the PC serial port TX pin and PIC serial data input pin to prevent damage to PIC.
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2 years ago: is the IR module a normal one? I think we can put a high powered IR device to make the distance farther from the target right?