Intro: Audio Transmission Through Body
Can we transmit data through human body? This question haunted me for a very long time. Then I came across a video where ericsson demonstrated such technology. The apparatus they used were big. So, I decided to work on this technology but decrease its size.
Step 1: Materials Required
The materials required for this project are common electronic components that one can find in some local electronic supplies store. This project mainly emphasis on the transmission of sound through the body. Its just a prototype that I built to test the theory. Lot of improvements have to be made.
1. 3 x BC547 transistors
2. Resistors- 2 x 150 ohms, 1 x 100 ohms
5. Breadboard or a perfboard
6. 6v to 9v power supply
1. 5k ohms potentiometer (preset)
2. Capacitors- 2 x 0.047 uf, 100uf, 220 uf
3. LM 386 audio amplifier IC
5. Breadboard or a perfboard
6. 9v power supply
7. Mono jack
Step 2: Transmitter
Transmitter is very easy to build. You can easily develop your own version of it as well. It is just an audio amplifier circuit where the speaker is replaced with a single output wire. This wire is the one that transmits small amounts of current through your body that is modulated corresponding to the audio input. This circuit is completely safe. Just refer the schematic diagram of the circuit to build the transmitter. Pins 1 and 8 are linked together using a 5k potentiometer. Pin 2 is connected to the input via a 0.047 uf capacitor. Pins 3 and 4 are connected to ground. Pin 6 is connected to the positive terminal of the battery and a 100 uf capacitor links it to ground. Pin 5 is the output pin. It is connected to the output wire through a 220 uf capacitor and a 1k resistor. You can change the value of this resistor to adjust the volume. Pin 5 is also linked to ground via a 10 ohms resistor and a 0.047 uf capacitor. If you have any doubts or suggestions regarding this circuit feel free to comment.
Step 3: Receiver
The receiver is even simpler than the transmitter. It is just a cluster of three transistors connected to each other. I used BC 547 transistor as it has a high gain and is very cheap as well. The resistors are connected to the collectors of T1 and T2 and to the emitter of T3. The emitter of T1 is connected to the base of T2 and the emitter of T2 is connected to the base of T3. The base of T1 has a wire attached to it that acts as a touch pad. If you have any doubts or suggestions regarding this circuit feel free to comment.
Step 4: Assembling the Circuits
These circuits are easy to assemble. Refer to the schematic diagrams of both the circuits to assemble them. I was in a hurry to complete this instructables so I might have made some mistakes. This project is just a prototype to test the theory that human body can act as a link between two or more devices. Lot of improvements have to be made to the circuits.
Step 5: Enhancements
Instead of connecting the output wire of the receiver to a speaker you can connect it to some powerful amplifier, such as the one in the car. If there is a need to amplify the incoming signal, just touch the positive terminal of the battery in the receiver circuit along with the Rx pin. This increases the current in the base of the transistor though it distorts sound.
Step 6: Inference
This experiment proves that data can be transmitted through human body efficiently with much smaller apparatus and cheaply.