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351 Advances in Natural and Applied Sciences, 5(4): 351-358, 2011 ISSN 1995-0772 This is a refereed journal and all articles are professionally screened and reviewed ORIGINAL ARTICLE Portable Solar Headphone Amplifier-The Feasibility Approved 1 Mohammad Syuhaimi and 2Ab-Rahman 1 Spectrum Technology Research Group (SPECTECH) Department of Electrical, Electronics and Systems Engineering Faculty of Engineering and Built Environment. 2 Institute of Space Science (ANGKASA) Universiti Kebangsaan Malaysia 43600 UKM Bangi, Selangor, Malaysia. Mohammad Syuhaimi and Ab-Rahman: Portable Solar Headphone Amplifier-The Feasibility Approved ABSTRACT Portable Solar Headphone Amplifier has the ability to receive the audio signal from the transmitter between range 5cm. The transmitter has the ability to convert the audio signal to light then the receiving part require to receive the light and convert it back into audio signal. This paper presents a simple analysis of receiver when supplied with signal generator at the transmitter, the receiver behavior has been presented. Experimental results are given to check the transmitter and receiver circuit validity. Key words: Transmitting, Receiving, audio signal and solar panel. Introduction Portable Solar Headphone Amplifier is a simple application project for a data transmission using solar cell. The is by converting the sound waves which propagated by air into light energy then converting back the light energy which received at the receiver to a electrical energy. The converting process is by increasing the power of the electrical energy using electronic circuitry then resulting the electrical energy back into physical energy in the form of sound waves. This headphone is require no cable and become wireless. User can direct listen to the music which plays from any portable player MP3 or CD players, iPods or computer or laptop. Using the headphone jack that transmit the music directly to the headphone which received the sound and amplified for boosting volume and improving the sound quality. The headphone not only can make the music louder, but more importantly the amplifier creates deeper, more powerful bass and clearer high frequencies at all volume levels. System Architecture: Fig. 1: Block Diagram of Portable Solar Headphone Amplifier. Transmitter: Figure 1 shows the block diagram for the connection to the portable solar headphone amplifier. The systems have two circuits. First circuit is transmitting the audio signal which is converted into the light. The signal will Corresponding Auther: Mohammad Syuhaimi, Spectrum Technology Research Group (SPECTECH) Department of Electrical, Electronics and Systems Engineering Faculty of Engineering and Built Environment. 352 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 be received on the solar panel and will be amplified and convert back to audio signal. The distance between transmitter and the receiver is in the range 5cm. Fig. 2: Transmitter Circuit (a) real world (b) PCB Layout. The transmitter part is consists of an audio male jack, a 10kΩ resistor, a 9V battery and the LED (Figure 2). A 9V Battery is used to provide voltage for the transmitter circuit. The resistor is used to limit the current flow in the circuit to avoid damage to the LED because the LED can accept voltage not more than 5V. Audio male jack is connected to the audio source which can get from PC, radio, phone etc. Receiver: Fig. 3: Receiver Circuit (a) real world (b) PCB Layout. The receiver part consist of a phototransistor detector SFH 350V, a 5V voltage, two resistors with 471Ω and headphone amplifier circuit. The prototypes of the receiver circuit as in Figure 3. When the optical signal from transmitter is received at the phototransistor detector, it will convert the optical signal to electrical signal and the signal is amplified where it becomes a sound wave. Operation: The input audio signals are converted to an electrical signal by audio jack and the signal is combined with the voltage from battery to the LED and produces an optical signal. The audio information is modulated and encoded into the light emitted by the LED. The processed being a result of the frequency of the light and transmit. When light strikes the receiver or the solar cell, a certain portion of it is absorbed within the 353 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. The cells also all have one or more electric field that acts to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current that flow from the metal contacts on the top and bottom of the solar cell. This current then was amplified to reproduce the audio signal. Fig. 4: Portable Solar Headphone Circuit. Analysis: The experiments have done to analyze the characteristics of the receiver when supplied with signal generator at the transmitter. The experiments are to analyze the relation between the transmission distance and received voltage, to analyze the output power with frequency transmitted of the designed circuit, to identify the current versus resistance characteristics and output frequency characteristic. The comparison using 5 different lengths of transmitter and receiver with the intensity of voltage received at the receiver circuit. The voltage characteristics was analysed by varying the distance as stated in the Figure 5. The output voltage is decreased when the distance is increased. This shows that the voltage is inversely proportional to the distance. The maximum distance that the light signal can transmitter to the receiver solar circuit of the headphone amplifier is 5 cm. Fig. 5: Various Distance and Value of the Voltage. The frequency was constant at 1kHz throughout the experiment to avoid any other effects on the results. Even though the expected results were obtained but the received voltage level is in millivoltage which is considered very low. The lower voltage due to the some unexpected noise which occured during the experiment. 354 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 Figure 6 show the analysis of the output frequency and power of the audio signal. The various frequencies are set from 1.000 Hz to 5.000 Hz. The potentiometer is used to adjust the frequency. Based on the result and ploted graph the power is increase if the frequency increase. The voltage is constant for this experiment which is 2.5 Volts. The total power received are directly proportional to the input frequency. Fig. 6: Power Obtained for variable Frequencies. The current versus resistance characteristics was tested by varying the resistance value as shown in Figure 7. The resistance value was controlled by using potentiometer which connected to the circuit as shown in the circuit description part. As expected, the current value was reduced when the resistance value increased. Fig. 7: Obtained current for variable resistance. The experiment has done to check the transmitter and receiver circuit validity. Transmission circuit was injected with 1kHz input frequency as shown in Figure 8 and the output was amplify to 4Khz as in Figure 9. Figure 10 and 11 shown the 1kHz and 2 kHz output frequency for variable distance. Fig. 8: Input signal 1Khz. 355 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 Fig. 9: Output signal 4kHz. Fig. 10: Received voltage at 1kHz frequency for variable distance. Fig 11: Received voltage at 2kHz frequency for variable distance. The experiment also done by using fiber optic to measure the distance and intensity of audio signal. Fiber optic power meter is the instrument that measures the average power of a continuous light beam and use to test signal power in fiber optic networks. The power intensity can be calculated by using the formula as shown below to get the exact value in decibel. 11.8 (1) 356 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 The fiber optic used to transmitting the signal as it has higher reliability and can transmit the audio signal in the longer distance. The fiber optic cable is placed between the transmitter part and receiver part. The signal that generated by the battery brighten up using blue LED that having the wavelength between 470 nm. This is the most suitable wavelength in transmitting the signal. The different experiments were conducted to measure the distance and intensity of the audio signal and the relationship between the voltages, current and power received. Figure 12 and Figure 13 shows the values of power intensity measured by power meter and calculated by using the formula (1) respectively. Figure14 shows the Average Power Intensity vs Length of Fiber optic calculated by using Formula 1 (exact scale). Fig. 12: Values of power intensity measured by power meter. Fig. 13: Values of exact power intensity by using the formula (1). Fig. 14: Average Power Intensity vs Length of Fiber optic. 3557 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 g is seet to 1.000 kHz as constant value. The rheeostat is used to The innput frequencyy of function generator adjust the resistance r of th he circuit. In thhis experiment,, the potentiom meter is used to set the constan nt frequency annd the voltagee that equal to 11 V. Rheostat is use to adj djust the resistaance value in this t experimennt. Figure 15 annd Figure 16 shows s the inpuut and output siignal tested at 1 kHz and 2 kH Hz. Fig. 16: Innput and outputt signal for 2KH Hz. Hz. Fig. 15: Innput and outputt signal for 1KH oltage versus Frequency. F Fig. 17: Vo v increases if the frequuency increasees. However, the t voltage is constant afterr the 3.000 kH Hz The voltage onwards. In I this test, thhe fiber optic of o 2m is usedd to conduct th he whole expeeriment. The relation r betweeen measured voltage v at diffeerent frequencyy is shown in F Figure 17. 358 Adv. in Nat. Appl. Sci., 5(4): 351-358, 2011 Fig. 18: Current versus Resistance. The basic principle used by rheostats is Ohm's law, which state that current is inversely proportional to resistance for a given voltage. This means the current decreases as the resistance increases, or it increases as the resistance decreases. The result that obtains from the experiment is following the ohm’s law. Current enters the rheostat through one of its terminals, flows through the wire coil and contact and exits through the other terminal. Rheostats do not have polarity and operate the same when the terminals are reversed. The produced current over the rheostat values is shown in Figure 18. Conclusion: The objective of this project to design and develop a portable solar headphone amplifier system to transmit and receive audio signals is achieved. In this project, two circuits were constructed and tested. The circuits designed are also suitable to be integrated for small world communication system such as inside a cruise ship or on an oil platform. Besides that, it is a low cost project and easy to construct. Both of the circuits uses light to transmits the audio signal but have difference in their circuit configurations. These two circuits have their advantages and disadvantages. However, after comparing both circuits is it found that the advantage of the transmission via fiber optic outweighs the advantages of the transmission in wireless environment circuit. Although it is more expensive compared to the transmission in wireless environment circuit, the transmission via fiber optic can transmit audio signals at longer distances and more efficiently. Overall, there are many ways to transmit audio signals such as through copper wires and radio waves. However, audio signal transmission using visible light is found to be low cost and simple to construct. Besides that, transmission using optical fiber is faster and more efficient compared to other methods. Future Work: Some recommendations for future improvements for this project is to improve the sound quality of the audio signal transmitted. This can be done by using amplifiers in the transmitter and receiver circuit. More research can be done to reduce the losses in the transmission system. The first circuit can be further improvised so that it can be able to transmit audio for longer distances. The solar cell can be replaced by photovoltaic cells higher sensitivity and efficiency. The second circuit which uses fiber in its transmission can be improved to be able to transmit a few channels that consists different audio signals. This can be done be using fiber optic multiplexer and splitter References Way, W., 1987. Large signal nonlinear distortion prediction for a singlemode laser diode under microwave intensity modulation. J. Lightwave Technology, LT-5: 305-315. Shun Liu and AtsuhiMinato, 2007. A New Lighting for Communication System for audio signal for white LED. J. Light & Vis. Env., 31(2): 65-69. Cox, C., III and Helkey, R., 1997. Techniques and Performance of Intensity-Modulation Direct-Detection Analog Optical Links. IEEE Transactions on Microwave theory and techniques., 45(8).