Laser Communication Circuit: The laser communication circuit detailed below enables wireless audio communication. With the incorporation of a parabolic reflector, the communication range can extend to several kilometers, and even at such distances, the sound transmission remains remarkably clear.
The circuit comprises both transmitter and receiver components. We utilized a specific laser diode emitting a 650 nm wavelength beam at a power of 5 milliwatts, akin to those found in common laser pointers.
Both the receiving and transmitting circuits operate on separate 9-volt batteries. The emitter circuit captures sounds via an electret microphone and emits the laser diode beam. The receiver, on the other hand, features a 4-36 ohm speaker and includes an amplifier. For effective operation, it’s crucial that the laser receiver and transmitter maintain direct line of sight. Notably, this system offers substantial security, making it difficult for unauthorized parties to intercept or eavesdrop. Additionally, an infrared (IR) laser diode can be employed, rendering the beam invisible to the naked eye.
LAZY SOUND TRANSMITTER SCHEMATIC
The laser current is set by VR1.
LAZY RECEIVER DYNAMICS CHART
Sound Transmitter Details: The typical operating current for the laser diode (5mW, 650 NM) falls within the range of 1-40mA, although it usually operates at 30mA. Beyond 80mA, the laser diode’s current diminishes, which can be detrimental. To prevent excess temperature damage, the metal sheath is removed. The circuit incorporates a 68 ohm NTC for temperature protection, ensuring the laser diode’s working life reaches approximately 20.00 hours.
The transmitter’s component arrangement includes a red LED, which pulsates rhythmically when sound signals are received, forming the Parts Placement Plan for both the Transmitter and Receiver components.
Receiver Details: In the receiver, the transmitted signal is captured by a photodiode. It’s essential to employ a photodiode that can detect visible light for this circuit. The receiver circuit utilizes the LM386 amplifier, powered by a small four-ohm speaker that draws 350mW from a 9-volt source connected to the coil.
Buyer Dynamics Part Placement Plan
The photodiode is directly mounted on the receiver board. It’s crucial to solder the laser diode carefully to prevent deterioration due to excessive heat, which can be mitigated with appropriate cooling measures.
To calibrate the system, start by opening the transmitter and adjusting VR1 to the halfway position. Then, turn it clockwise gradually, increasing the current until the laser diode emits light. Additionally, the LED should flicker when sound is detected through the microphone. Notably, the laser beam should remain stable during this process.
Position the receiver and transmitter one meter apart. Upon powering the receiver, the speaker’s volume becomes visible. If necessary, a piece of paper can be placed in front of the photodiode to reduce excessive noise. However, it’s important to note that this paper should not be used during regular operation, as it would increase the distance. This setup allows the microphone output to be controlled by the speaker output.
Laser Sound Printing Circuit
Emitting Material List
Resistances
R1 4.7k
R2,3 1 00k
R4 68k
R5 10k
R6 4.7M
R7 220k
R8-1 0 220 ohm
Rl 1.12 47k
R13 56 ohm 1 / 2W
R14 68 ohm NTC thermistor
VR1 1 00k trimpot
Capacitors
Cl, 2 1OuF 16V
C3 4.7uF 16V electrolytic
C4,5 10OuF 16V electrolytic
C6,7,9 68nF
C8,1 0 0.47uF without polarity
Semiconductors
LED1 5mm green LED
Laser 5mW / 65Onm laser diode
Ql, 2 BC557 PNP
03 2N5484 N-ch JFET
Dl-7 1N4148 signal diode
D8,9 1 N60 germanium diode
lci 7805 5V regulator
1C2 LM358 op-amp
PCB 65mm x 36mm
8-pin IC socket; 9V battery and battery clip.
Receiving Material List
Resistors
Rl 680 ohm
R2 22 ohm
R3 4.7k
R4 39k
R5 3.gk
R6 10k
R7 1k
R8 220 ohm
Rg 4.7 ohm
VR1 50k trimpot
Capacitors
Cl, 2,5,7 10OuF 16V electrolytic
C3,4 1 uF 16V electrolytic
C6 15nF polyester
Qi BC549 NPN
LM386
ZD1 5.6V 40OmW zener
PCB 36mm x 64m
Photo diode
9V battery
Speaker
8 pin integrated socket
