@▷ Infrared Modulation Identifier Via Remote Control | Diagram for Schematic

Infrared Modulation Identifier Via Remote Control

Circuit Project Description

The circuit illustrates how the modulated carrier of infrared is measured by displaying the waveform on a frequency counter after the signal received is amplified.

Remote control – an electronic device that has an infrared LED that sends out pulses of invisible lightInfrared – an electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than that of terahertz radiation (3-300 um) and microwaves (~30,000 um)Photodiode – a device that acts as a source of current that increases with the intensity of light Circuit Explanation

The photodiode used in the circuit was TIL100 which is a high speed photodiode operating in a reverse bias mode with high sensitivity and fast response. It was designed to be utilized for infrared remote control system. When the photodiode is focused on the IR range, it produces minimal but steady current corresponding to the steady light. The low noise transistor BC549C amplifies the input signal from the 10nF capacitor. Light intensity will not change when the capacitor discontinues the steady light. Some signal will be delivered to the amplifier from the photodiode. On the frequency counter or oscilloscope, the voltage waveform will be displayed produced by the high current gain of BC549C and a medium load resistor. There will be no accurate reading as the scale will vary with the distance from photodiode to remote control. When control pulses are combined with the carrier, a frequency meter or counter is best set to measure the period of the wave, rather than the frequency.

Most IR remote control are using signals modulated with a high frequency carrier wave which is invisible to the human eye. Due to the fact that the pulses of a normal remote control are long, a few complete waveform can be measured. The remote control is best positioned near the remote control to avoid much interference like the light from a fluorescent light. The lower sensitivity of a frequency counter requires the signal to be processed further. The period of the waveform can still be measured even in the existence of phase shift from input to output or turning a sinusoidal waveform to digital.


Independently, the usage of remote control may be for controlling substation, pump storage power stations, plants, radioactive and toxic environments to avoid human casualties, in military jammers and countermeasures against jammers, space travel, and other PC applications. The infrared may be used as filters, night vision, thermography, tracking, heating, communication, spectroscopy, meteorology, climatology, astronomy, art history, biological systems, photobiomodulation, and health hazard.

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