The circuit of Figure 1 modulates an infrared emitter LED from audio signals or low frequency data applied to its input.
The power supply must be symmetrical and equivalent operational amplifiers can be used, including types with a frequency response greater than 741.
The gain of the circuit is determined by the ratio of R3 to R2. R2 can be changed as a function of the signal strength used in the modulation. The LED can be of any infrared type.
In Figure 2, we have a suggestion for a printed circuit board for implementation of this emitter.
Optical features, such as lenses, can be used to focus the radiation in one direction and thus achieve greater range.
The MIN242E can be used as receiver for this transmitter. Its outputs should be connected to appropriate amplifiers.
MATERIAL LIST
CI-1 - 741 - operational amplifier
LED - LED common infrared emitter
R1, R2 - 1 k ohm x 1/8 W - resistors
R3 - 220 k ohm x 1/8 W - resistor
R4, R5 - 560 ohm x 1/8 W - resistors
C1 - 1 uF - polyester capacitor
Miscellaneous:
Printed circuit board, symmetrical power supply, wires, welding, optical resources, etc.
