Designing an Electronic Stethoscope - Lab Report Example

Topic: Introduction This is a project aimed at designing an electronic stethoscope. The circuit is built using a PCboard and battery as source of power. Resistors, ohms and capacitors are used to regulate voltage and current flow. The Stethoscope is an auditory medical appliance for listening to internal resonance in human body which is referred to, in medical language, as auscultation. Heart sound vibration is one of the most essential ways to judge the condition of the cardiac function. Components functions LM386 Low Voltage Audio Power Amplifier is an auditory amplifier designed for exploitation in low electrical energy consumer purpose which provides both current gain and voltage for signals. Hence, power amp with variable gain is considered with the assistance of op-amp LM386. It acts as a low-noise microphone pre-amp. Its gain is approximately 3.9 because the high productivity impedance of the exhaust of the FET within the electrets microphone makes efficient input resistor to be approximately 12.2K. MPF102 Transistors’ purpose is to manage current by an electric field; voltage produces only a small raise in drain current. 1K Ohm 1/4-Watt Carbon Film Resistor provides accurate amounts of resistance in electric circuits. Resistors are marked both in regards to their resistance (1K ohms) and their capability to dissipate high temperature energy (1/4-watts). 1M Ohm 1/4-Watt Carbon Film Resistor refers to 1M ohm resistance and a quarter heat dissipation. 10 ohm 1/4W 5% Carbon Film Resistor and 4.7K Ohm 1/4-Watt Carbon Film Resistor likewise give the corresponding resistance and dissipation. (x2) 0.047µF 50V 10% PC-Mount Capacitor separates the microphone route from the LM324 quadruple functioning amplifier. This way, the LM386 can operate at the full 12 V without hindering the voltage of the microphone circuit. 0.1µF 50V Hi-Q Ceramic Disc Capacitor also operates on the same basis of the above capacitors, however, in regards to its ratings. Project Enclosure (3X2X1") has Project Box, Aluminum Lid and Plastic lid. This enclosure comprises four standoffs in the base corners to sustain a PC board. Standoffs are 1/4" far above the ground with holes that allow sharp 4 screws. Slots are available on all four sides of the apparatus to allow a PC board to be fixed horizontally or vertically alongside the length or breadth of the enclosure. Enclosure has aluminum and plastic lids. Multipurpose Pc Board with 417 Holes is a grid-style PC plank as the starting point for electronics task. It includes 417 pre-drilled punctures. The board measurements are 1.875 inches by 2.875 inches. JVC GumyEarBuds represent an improvement in comfort, fitting the ear with an exceptional curved housing. The big 0.53" (13.5mm) neodymium components in these blue earbuds convey a superior listening practice. 10K-Ohm Linear-Taper Potentiometer: B10K 17mm With Dust fasten has modifiable top with power of 1/2W, Resistance: 10K OHM OHMS, Knurled Shaft, Shaft Diameter: 6mm, Shaft Length: 10mm, Suits Most Standard knobs, Mounting Hole: 7.5mm and Base Diameter: 16mm. Hexagonal control knob 1-1/4" length by 5/8; Sold in packages of two. 1/8" Mono Panel-Mount Audio Jack; NOTE: This component does come with the anchoring nut to assist in fixing. Specifications: type: mono, with insert switch, solder connections and in housing. This 6-foot insulated cable features a 1/8" handset plug on each terminals. Shielded to safeguard signal potency and guard against buzz. Also, a 6-foot lead has a 1/8" handset plug on each terminal also insulated to preserve signal power and guard against hum. Fully Insulated 9V Battery Snap Connectors: has 9V snap connector for substitutes or projects. It has color-coded cable leads and also connects to our battery holders that possess snap connectors; it also uses replacements for projects, and its color-coded wire leads to avoid confusion and Package of 5 of the relevant elements. Enercell® Alkaline 9 Volt Battery is the source of energy (Tang, Guitao & Hao Li, 2010). How does the component work in the circuit? U1a acts as a low-noise microphone pre-amp. Its increase is only approximately 3.9 since the high productivity impedance of the drain of the FET within the electret microphone makes an effective input resistor to be approximately 12.2K. C2 has a moderately high value in order to bypass very low frequency of approximately 20 to 30Hz heartbeat sounds. U1b function as a low-noise Sullen and input, Butterworth low-pass-filter by means of a cutoff occurrence of in relation to 103Hz. R7 and R8 offer an increase of about 1.6 and permit the use of identical values for C3 and C4 but tranquil producing a pointed Butterworth reaction. The roll off pace is 12dB/octave. C3 and C4 can be abridged to 4.7nF to boost the cutoff frequency to 1 KHz to listen to respiratory or mechanical sounds. The U4 route is optional and has an increase of 71 to coerce the bi-colour LED. U5 is a 1/4W power amp IC with fitted biasing and inputs that are passed on to ground; it has a gain of 20. It can make any kind of headphones involving low impedance 8 ohms ones. The target resonances originate from the sensations of the stethoscope’s slim diaphragm, and the noise waves resound through the rubber cylinder. This tubing operates as a mechanical low pass sieve, assisting in copying the original sound of an electronic stethoscope. Situated at the end of the cylinder is a condenser microphone enclosed in a plastic coupling apparatus designed in Solid Works and scribbled on a 3D printer. The indicator is then sent the rough a DC jamming capacitor accompanied by a non-inverting electrical energy follower, a second-order low overtake filter, and lastly an active gain stage giving a gain of 10. The corner regularity for the filter reflects as 800 Hz. Before the signal is circuited to the desired sound outputs, it is focused to voltage dissipation by a potentiometer that operates as a volume control. The speakers at this time being used are rated for five watts at four ohms. For headphone strengthening, the LM386 was selected and offers an ostensible gain of 20. In order to impel the speakers, a high-powered TDA2003 was preferred to offer a gain of 100, which can be changed by different capacitor and resistors values within the circuit. This device derives 12VDC and pulls about 100mA at climax speaker output from a variable energy supply. The compilation of single supply outfitted amplifiers utilizes an essential ground of 6 volts, produced by a series of buffered electrical energy dividers. The covering for the main receiver package is a clear polycarbonate box which has the speakers and all the client controls including energy switches and volume gearshift for both speakers and headphones. On the part of the box is a tiny hole for the input leads from the condenser microphone, with the cover to the enclosing being secured by six screws. Theory of each component Theoretically, 1-1/2" flat round cabinet knob is a Flat Round Knob Molds Re-utilizable six 1/2 oz cavities and 1 ? inches in diameter. - LM386 Low Voltage Audio Power Amplifier theoretically is a speaker amplifier and modulator. It is believed to be a low-voltage audio power amplifier which is easy to build with few components. Its IC is designed to deliver a voltage amplification of twenty without additional add on parts. MPF102 Transistors by convention, the terminal upon which current is supplied is called the supply terminal since, as far as the transistor is concerned, the current begins from this terminal. The other terminal is known as the drain terminal. Current stream between source and drain is correlated to the drain-source electrical energy by the resistance of the superseding material. There are different transistors and modes of their functions which form the basis of difference between each other. 1K Ohm 1/4-Watt Carbon Film Resistor is a passive electrical component with two terminals that implements electrical resistance as circuit component. Theoretically, the current through a resistor is in direct proportion to the electric power or voltage through its terminals. PC-Mount Capacitor involves a surface-mount technology (SMT) method for building up electronic circuits in which the components are fixed directly onto the outer surface of printed circuit boards (PCBs). An electronic gadget so made is referred to a surface-mount device (SMD). In firms, it has largely substituted the through-hole technology assembly method of fitting gears with cable leads into holes in the circuit board. Both technologies can be utilized in the same board for components not appropriate to surface mounting such as heat-sinked power semiconductors and transformers. Radial-lead Electrolytic Capacitor is a type of capacitor that utilizes an electrolyte, an ionic transmitting liquid, as one of its component, to attain a larger capacitance per unit quantity than other types. It is used in relatively low-frequency and high-current electrical circuits, particularly in power supply filters, where it stores charge required to moderate output electrical energy and current variations in rectifier output. It is also widely used as pairing capacitors in circuits where AC ought to be conducted, but DC must not. 0.1µF 50V Hi-Q Ceramic Disc Capacitor is constructed with resources such as titanium acid barium designed for dielectric. Internally this capacitor is not constructed as a coil, so it is well-suited for exploit in high-frequency applications. It is characteristically used to by-pass high rate of recurrence signals to ground. It is shaped like a disk, obtainable in very low-capacitance values and very tiny sizes. Project Enclosure (3x2x1") is an electronic science kits enclosure which is constructed by durable ABS plastic. It features four stand-offs at the lower part to support the PC board. The standoffs are a quarter high with holes supporting four sharp screws. Measurement 3x2x1 implies product width of 3 inches by product length of 2 inches by product height of 1 inch. Multipurpose PC Board with 417 Holes is a grid-style PC board used as the starting point for developing electronics project of a stethoscope. The PC board includes 417 pre-drilled holes. The board measurements are 1.875 inches by 2.875 inches. JVC® GumyEarbuds is a gadget that protects the ears from electromagnetic effects during the use of electronic stethoscope. It is made up of powerful 13.5mm Neodymium driver unit also shaped to fit the ear comfortably. 10K-Ohm Linear-Taper Potentiometer is a three-terminal resistor with a switching contact that makes an adjustable power divider. If only two end or junctions are used, one end and the wiper, it works as a rheostat or variable resistor. Potentiometers are generally used to manage electrical pieces of equipment such as volume controls on audio equipment such as stethoscope. Hexagonal Control Knob is a control component used to regulate the voltage and other measurements to get the correct reading. The shape makes it easy to use during winding to give correct reading. 1/8" Mono Panel-Mount Audio Jack is open-frame, open-circuit jack that accepts 2-conductor terminals or plugs to facilitate its function. Size 1/8"-diameter. Package of three, an open circuit, a 2-conductor, solder terminals and nickel plate are the basic components of this jack. Fully Insulated 9V Battery Snap Connectors are battery snap connectors to make use of PP3 type 9V battery or battery supporters with snap terminals. Pack of two 9V snap terminals for substitution or projects. It has 100mm color-coded wires and also anchors to battery holders that possess snap connectors. 90dB Piezo Pulse offers means to loud audio output, low current utilization and high stability. 90dB Piezo Pulse functions on 3-28VDC, transferring 12mA at 12V and in addition has a buzzer tone rating of 2,800Hz. How the heart beat goes through the circuit. The heart beat is captured by the microphones which capture the vibration of the heart and pass to the circuit. Two microphones supply into two quadruple outfitted amplifiers that amplify and sieve the signals. From the two op amps apparatus, the signal goes through a single mixer. Here, the sound is additionally filtered and amount, bass, treble, and balance amid the 2 signals can be changed. A switch then transmits the yield to an amplifying circuit for the headphones or speakers, from which resonance can be heard. The circuit is energized by 12 VDC. Per the client’s demand, there are two different microphone inputs. Since it can only manage 2 V, a voltage separator is used to reduce the power incoming the microphone. A voltage separator consists of two resistors: one from earth and one from the 12 V supply. Their point of connection has the devised 2 V, which is the electrical energy source for the headphones. The circuit and equation illustration for a voltage separator can be seen in a capacitor that divides the microphone circuit commencing from the LM386 quadruple outfitted amplifier. This way, the LM324 can task at the complete 12 V without distressing the electrical energy of the microphone track. The LM317 A voltage controller is also applied. This voltage control device keeps a hovering input electrical energy of 6 V with railing at 0 V and 12 V. Voltage is hovered in order to permit the frequency to alternate with higher amplitude. A ground-referenced electrical energy would originate the signal to “rail out”, striking these voltage rails and mislaying some of the indication. The LM324 has four independent op amps associated in series. The first two are reverse amplifiers utilized for amplitude gain. The first amplifier has a gain of 1 while the subsequent has a gain of 3. The gain is measured or produced by the resistors associated to the inverting supply. The other two op amps contained by the LM324 are utilized as a 5-pole Sallen-key low-pass sieve with a corner rate of recurrence of 1000 Hz. Noise frequencies over 1000 Hz will be considerably reduced until frequencies more than approximately 1200 Hz will not be captured at all. The signals imminent from the two LM386 quadruple op amps together supply into the LM1036 mixer. The LM1036 comprise potentiometers to manage bass, balance, treble, and volume. To eradicate background sound in the stethoscope, treble resonance is abridged while bass is amplified. This permits for low heart resonances to be heard more prevalently. The amplifiers, resistors and capacitors play a major role in conveying and relaying sounds during heart beat measurements. Some of the problems encountered with the design. The problems encountered during the development are missing some of components for successful design. The most notable mistake was the wrong usage of Medical Piezo instead of 90dB Piezo Pulse, which rendered experiment failure. The Piezo used was wrong, and for the next week experiment the correct Piezo has been ordered; by then, experiment will be complete. Other missing components could be improvised. When the ordered Piezo is delivered, we will test it first to access its functionality and then put it into correct connection. Fixing the problem is the order of correct Piezo and additionally improvising others that may not be acquired. However, this is done with great caution since this is an electrical project where any wrong component could pose a danger. Work Cited Tang, Yang, Cao Guitao, and Li Hao.“The design of electronic heart sound stethoscope based” 4th International Conference on Bioinformatics and Biomedical Engineering (ICBBE), 2010. 1-4. Print. Read More