This project describes how to build an IR remote control extender / repeater to control your electronic appliances from a remote location.
An IR detector module receives IR signal from remote control and two IR leds are re-emitting the signal to the appliance. You can place the IR emitting leds close to the device you would like to control using some wire and keep main unit close to remote control location. In the image at the left LEDs are soldered on the board. The circuit consists of three main parts, the IR receiver module, a 555 timer configured as an oscillator and the output / emitter stage. We will describe circuit operation below.
IR Signal
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. The signal consists of two parts, the control pulses and the carrier wave as seen in the image below.
A common frequency used for the carrier is 38KHz and control pulses frequency is in the range of 1-3KHz. The carrier signal is modulated by the control pulses and the resulting signal is emitted by remote in IR band of electromagnetic spectrum. IR band is invisible to human eye. You can see if an IR led is emitting light or not using a camera. Point the camera to the led and you will see that light comes off.