5. Crude Laser communication module

< Intro >

To start with, this project involves hearing audible sounds from a distance using the power of a laser. The concept in itself is fascinating as of course, unlike the common method of transmitting signals through means such as radio, wifi, etc, you use the laser as a way to send data from the transmitter, and to the receiver. In addition, the circuit is simple as it takes only a few components for the transmitter, and even less so for the receiver part.

< How it works> 

It all begins with the audio source as an input, whether it be music, your voice to the microphone, or any other. It then goes to the transistor's base (along with other passive components to limit the noise from the input and bias the voltage for the base) where it can control the transistor's main current from the collector and to the emitter based on the fluctuating current from the input(AKA the audio signal itself).  Since the voltage is much higher on the collector, it effectively means that the transistor manuplating the current increases the current gain in order to power up the laser, and controls the brightness/intensity from the transistor.

Once the data-carrying laser is shooting the beam into the receiver, the receiver will take those intensities and convert them into a current that has all the fluctuations in place, similar to how the audio signal is being carried through wires. And just like with any audio source, it's then connected to the amplifier, where it would boost the current up and outputs the sound out with speakers.

<Transmitter module>

In terms of designing this whole project together, everything was all set up in a bird's nest configuration, where the components were soldered together without using a PCB. There, the 4 AA battery holder will be the entire base for the module, as well as the only power source for the transmitter part. For the receiver, all it takes is using either a solar panel or a light-dependent resistor(it needs to be powered for the LDR to work properly), which is then connected to the input of the amplifier (or a set of amplified earphones if you want to make it more private.) and you are basically done. The only thing that is hard is trying to aim the laser at the receiver, especially when the 2 parts are far away from each other.

<Setup>

Overall, I feel like this project demonstrated the use of light for transmitting data (circuit shown below), and that it's another way rather than the most common. There are lots of things I could have improved on such as a better laser module, and a proper amplifier for the transmitter, but at this point, it did its function pretty well.

<Laser Communicator circuit>