Have you ever imagined the possibility of hearing the light? What interesting discoveries could you make by going around wielding an electronic ear that can turn sound into visible light and even invisible light like infrared?
It is this possibility that we give you with a simple design that is based only on an integrated circuit and is powered by common batteries.
What we have is an audio amplifier and at its entrance we connect a sensitive phototransistor (of any type) that is characterized by responding to both the visible spectrum as well as infrared and even ultraviolet radiation.
Pointing the sensor to a fluorescent lamp, for example, we will hear the snoring of the power grid, which causes the gas inside to vibrate with alternating ionization.
Pointing to a traditional analog TV screen, we will hear the sharp sound of the scan and the oscillations of the image and, together, the serious tone of the frame changes.
The complete circuit of the apparatus for listening to the light is shown in figure 1.
In figure 2 we have the arrangement of the components on a printed circuit board.
The set fits in a small plastic box whose dimensions must be chosen according to the battery holder and the small speaker of 5 cm or so.
As a sensor, we can use any ordinary phototransistor. The small 8-ohm foot speaker and small alkaline batteries are indicated for power.
Potentiometer P1 acts as a sensitivity control and is not critical and types from 10k to 100k ohm can be used. To test the device, simply point the sensor at a fluorescent lamp and open the volume. There must be reproduction of a snore.
Material list
CI-1 - TDA7052 - Integrated Circuit
FT - Phototransistor
R1 - 10k ohm - resistor - brown, black, orange
P1 - 1 M ohm - Potentiometer
C1- 220 uF x 6 V-electrolytic capacitor
S1 – On/Off switch
FTE - 8-ohm speaker 5 cm
B1- 6 V- 4 small batteries
Miscellaneous:
Printed circuit board, mounting box, wires, solder, etc.
