555 Infrared Transmitter-Receiver

Infrared transmitter and receiver circuit shown in the schematic diagram below can be used as remote control. The transmitter is basically an oscillator circuit, and the frequency can be adjusted using R1 potentiometer (or trimmer pot). This oscillation makes sure if the signal can be distinguished from other source by the receiver.

The receiver is actually a bandpass filter which filter out noise signal. The frequency of this filter is determined by L and C in the feedback path (from output to inverting input of the op-amp). D1 is inserted in the feedback path to enable rectifying very small signal, since the op-amp feedback mechanism will compensate the forward drop voltage of the diode. The last op-amp is employed as a comparator, with the threshold is adjustable via R3 potentiometer. The op-amp should be supplied with + and – 12Volt, and the R3 potentiometer should be supplied with -12V. [Circuit’s schematic diagram source: hobbyprojects.com]