If we are using a video extension from a TV, DVR, DVD player etc, we will come across a problem of controlling the main unit from a remote place from which the ordinary IR signals can not reach the receiver. For an example, if you have installed a satellite TV receiver in the living room or in the down stairs and a display in a bed room or in the up stairs, every time when you want to make any change you have to peep in to the place where the main unit is. But in this case if you can control the main unit from where the display is, how comfortable you will be? OK, I have designed a circuit for that and tested. It worked very well. It is a very simple circuit designed using commonly available inexpensive components excepts IR sensor module.
This is the Circuit diagram.
Circuit Description
The main function of this circuit is to receive the IR signal from a remote place by the IR sensor module and emit that near the main unit using IR LED s. So as shown in the
circuit diagram, you have to keep the main circuit in the place where the IR remote controller is (eg: in the room) and IR LEDs near the main unit (eg: in the living room). So LED s should be connected using a long wire.
As the IR sensor module, you can use a commonly available device. But it should be sensitive to the main unit's remote controller. As you know IR signal is not a pure digital signal. It is a modulated signal with a frequency around 400 kHz. It is done so mainly to eliminate interference from the environment. IR sensor module demodulates the IR signal and output digital signal. So we can not use that signal to light IR LED s near the main unit. Before emitting through IR LED s the demodulated signal should again be modulated with a wave having frequency around 40 kHz. IC1-c and IC1-d has been set as an astable multi-vibrator to generate the required frequency. Use VR1 preset to tune the circuit.(when you generate the correct frequency the circuit will work fine). The circuitry built with T1 and T2 transistors modulate this wave and the digital signal. Ultimately it is emitted near the main unit by IR LED s. For these, a current limiting resister is not generally needed, as they are turned on only for few milliseconds. If you experience burning of your IR LED s, just use a resistor of few hundreds ohm in series with them.
