Object IR Remote Extender
This project describes how to build an IR remote control extender / repeater to control your electronic appliances from a remote location.
The IR signal emitted from a remote control caries the information needed to control the appliance. This signal consists of pulses that code 0 and 1 bits, instructing the appliance to do a certain operation. One of the most common protocols used to code the IR signal is Philips - RC5 protocol.
IR signal is received by TSOP1738. TSOP1738 is an infrared receiver at 38KHz. At the output of infrared receiver we get a demodulated signal that means we get the low frequency control pulses. Infrared receiver is powered from C1, R1 and Z1 that forms a 5V power supply. With no signal received, infrared detector output is high and Q1 is on, so pin 4 of IC is LOW and 555 timer is in reset state. Q1 also acts as a level shifter that converts 5V signal of TSOP1738 to 9V signal for IC1.
Circuit IR Remote Extender
When HIGH control pulses are appearing on TSOP1738 output then
timer 555 (which is configured as an oscillator) starts to oscillate at a preset frequency, for the duration of each data pulse. That means that at pin 3 we get a signal that is similar to modulated source signal. It has a carrier component and a control pulses component.