Simple Low-pass filter Circuit Diagram

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This Simple Low-pass filter Circuit Diagram nonlinear, passive filter circuit rejects ripple (or unwanted but fairly steady-voltage) without appreciably affecting the rise time of a signal. The circuit works best when the signal level is considerably lower than the unwanted ripple, provided the ripple level is fairly constant. The circuit has characteristics similar to two peak-detecting sample-and-hold circuits in tandem with a voltage average.

 Simple Low-pass filter Circuit Diagram


Simple Low-pass filter Circuit Diagram
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Universal Compander Circuit diagram

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Signet type NE575 compander IC is intended primarily for use with battery power supplies of 3 to 7 V (max. 8 V). Itdraws a current of 3.5 mA at 3 V and 5 mA at 7 V. The compander process (compression at the input, expansion at the output) significantly improves the signal-to-noise ratio in a communications link. 

 Universal Compander Circuit diagram

Universal Compander Circuit diagram


The IC contains two almost identical circuits, of which one (pins 1 to 9) is arranged as an expander. The other (pins 11 to 19) can be used as expander, compressor or automatic load control (ALC), depending on the externally connected circuit. For the compressor function, the inverting output of the internal summing amplifier is brought out to pin 12. 

This is not the case in the expander section, where a reference voltage is available at pin 8. This pin is interlinked to pins 1 and 19 to enable the setting of the dc operating point of the op amps. The op amp in the expander section, pins 1 through 3, serves as output buffer in the compressor section, pins 17 through 19 as the input buffer. The IC has a relatively high output sensitivity and is evidently intended for processing small signals (microphone output level). 

A signal of 100 mV, for instance, is amplified by 1 only. The present circuit caters to larger input signals (line level); its maximum input level is 1.5 Vrms. With a 1-V input into R13, a potential of about 500 mV exists between compressor output R7 and expander input R5. The compression characteristic is shown in Fig. 19-2 (b). The signal range is reduced by about one half at the output, which is doubled in the expander. Thus, the range after compression and expansion is the same again, but that is not necessarily the case with the input and output level. The compander can be arranged to provide a constant attenuation or amplification. With the circuit values as shown in the diagram, the input and output levels are the same. 

The prototype had an overall gain of 0.5 dB when the expander input was connected directly to the compressor output. To allow acceptance of high input levels, R13, R14, and the compressor input resistance form a 10:1 attenuator. At the expander input, R5 and the expander input impedance of about 3 kfl form a potential divider. If the compander is to be used with smaller signals, the attenuation can be reduced as appropriate. If the input level lies below 100 mV, R5, R13 and R14 can be omitted. The compander covers the frequency range of 20 Hz to 20 kHz, the overall distortion is less than 1%, and the signal-to-noise ratio is about 80 dB.
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Vocal Eliminator Circuit Diagram

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Otherwise properly mixed sounds often suffer from a predominant solo voice (which might, of course, be the intention). Ifsuch a voice needs to be suppressed, the present circuit will do the job admirably. The circuit is based on the fact that solo voices are invariably situated `at the center` of the stereo recordings that are to be mixed. Thus, voice levels in the left- and right-hand channels are about equal. Arithmetically, therefore, left minus right equals zero; that is, a mono signal without voice. 

 Vocal Eliminator Circuit Diagram
Vocal Eliminator Circuit Diagram

 There is, however, a problem: the sound levels of bass instruments, more particularly the double basses, are also just about the same in the two channels. On the one hand low-frequency sounds are virtu--ally nondirectional and on the other hand, the recording engineers purposely use these frequencies to give a balance between the two channels. However, the bass instruments can be recovered by adding those appearing in the left + right signal to the left-right signal. 

The whole procedure is easily followed in the circuit diagram. The incoming stereo signal is buffered by A1 and A2. The buffered signal is then fed to differential amplifier A3 and subsequently to summing amplifier A5. The latter is followed by a low-pass filter formed by A6. You can choose between a first-order and a second-order filter by respectively omitting or fitting C2. Listen to what sounds best. The low-frequency signal and the difference signal are applied to summing amplifier A4. 

The balance between the two is set by PI and P2 to individual taste. You have noticed that the circuit does not contain input or output capacitors. you wish, output capacitors can be added without detriment. However, adding input capacitors is not advisable, because the consequent phase shift would adversely affect the circuit operation.
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Simple Notch filter uses an Operational Amplifier

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This notch filter is useful for tunable band-reject applications in the audio range.The values shown will give a tuning range of about 300-1500 Hz.

 Notch filter uses an Operational Amplifier Circuit Diagram

 Notch filter uses an Operational Amplifier Circuit Diagram

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Simple Noise limiter Circuit Diagram

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This Noise limiter Circuit Diagram improves signal-to-noise ratio. It is connected between the detector output and the audio input (if high impedance) or at some relatively high-impedance section between two audio stages—preferably the low level stages.D1 and D2 can be any diode having relatively low forward resistance and very high back resistance. The circuit is excellent for receivers having bandwidths down to 2 or 3 kHz. Increase the value of Cl for receivers having narrower bandwidths . 

Noise limiter Circuit Diagram


Noise limiter Circuit Diagram

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Glasses Mounted Automated Perimeter

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We have developed an instrument for performing a visual field test built into a pair of glasses. A visual field test maps out a patient’s visual field including peripheral vision and blind spots, and is useful for the diagnosis of several ocular and neural degenerative diseases including glaucoma, stroke, and brain tumors. Existing devices are bulky and expensive. We were able to create a low cost, portable version of this tool which makes it more accessible to doctors.

The final product.
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Final year Project Ideas

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  Bio-instrumentation Final year Project Ideas
  • Blood pressure
    • Arm pulse/ox and ECG to get vital signs (including blood pressure by P-wave velocity)
    • Doppler blood flow meter
    • Blood pressure cuff.
  • ECG/heart
    • ECG using capacitative electrodes on arm or fingers.
    • ECG using RF coupled passive sensors.
    • ECG with advanced QRS detection.
    • ECG with improved noise removal 
    • Electronic stethoscope and heart sound analysis.
    • Transistor hardware model of the heart with model pacemaker and defibrillator.
  • Impedance
    • GSR and skin impedance measurement.
    • Impedance tomography.
  • Eye
    • Eye-motion measurement by IR or camera or electro-ocular methods.
    • Pupil servo cnaracterization 
  • Functional imaging
    • IR tomography -- Functional Near-Infrared brain imaging.
  • EMG
    • Correlate and model IR reflectance with EMG.
  • Oscillators
    • Hardware model of gene oscillator
    • Nonlinear oscillator synchronization
  • Infrastructure/instrumentation
    • Analog adaptive 60 Hz filter. (LMS or other algorithms)
    • Adaptive filters for ECG/EMG 
    • Eliminate the DAQ6008 interface and use audio input to the computer.
  • Joint/sports
    • Wireless knee angle sensor.
  • Acoustic
    • Measure head-related transfer function and synthsize sound using it.
    • Oto-acoustic response
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Build a Derived Center-Channel Stereo System Circuit Digram

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A simple method of deriving a center or third channel without the use of an extra transformer or amplifier, (a) 4- speakers are connected to 8- amplifier taps. 8 and 16- speakers connect to 16- taps, (b) By blending the inputs it is possible to cancel out undesired crosstalk. 

Derived Center-Channel Stereo System Circuit Digram
 
Derived Center-Channel Stereo System Circuit Digram
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Battery-powered-high-voltage-generator Circuit Diagram

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Battery-powered-high-voltage-generator Circuit Diagram . Output voltage great enough to jump a l-inch gap can be obtained from a 12-V power source. A 555 timer IC is connected as an astable multivibrator that produces a narrow negative pulse at pin 3. The pulse turns Ql on for the duration of the time period. The collector of Ql is direct-coupled to tbe base of tbe power transistor Q2, turning it on during the same time period.  

The emitter of Q2 is direct -coupled through current limiting resistor R5 to the base of the power transistor. Q3 switches on, producing a minimum resistance between the collector and emitter. The high-current pulse going through tbe primary of high-voltage transformer Tl generates a very high pulse voltage at its secondary output terminal (labeled X). The pulse frequency is determined by tbe values of Rl, R2, and C2. The values given in the parts list were chosen to give the best possible performance when an auto-ignition coil is used for Tl.  

Battery-powered-high-voltage-generator Circuit Diagram

Battery-powered-high-voltage-generator Circuit Diagram
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Power Mosfet Inverter Circuit Diagram

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This Power Mosfet Inverter Circuit Diagram can deliver .high-voltage ac or de, with a rectifier and filter, up to several hundred volts. The secondary and primary of T1-a 12.6 to 440 V power transformer, respectively-are reversed; e.g., the primary becomes the secondary and the secondary becomes the primary. Transistors Q1 and Q2 can be any power FET. Be sure to heat sink Q1 and Q2. Capacitors C1 and C2 are used as spike suppressors. 

Power Mosfet Inverter Circuit Diagram


Power Mosfet Inverter Circuit Diagram

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Battery charger with LM317 Circuit Diagram

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Battery charger with LM317 Circuit Diagram. An LM317 voltage regulator is configured as a constant-current source. It is used to supply the 50 mA charging current to S01-S06, an array of AA-cell battery holders. Each of the battery holders is wired in series with an LED and its associated shunt resistor. When the battery holder contains a battery, the LED glows during charging. Each battery holder/LED combination is paralleled by a 5.1-volt Zener diode. If the battery holder is empty, the Zener conducts the current around the holder. 

A timing circuit prevents overcharging. When power is applied to the circuit, timing is initiated by IC2, a CD4541 oscillator/programmable timer. The output of IC2 is fed to Ql. When that output is high, the transistor is on, and the charging circuit is completed. When the output is low, the transistor is off, and the path to ground is interrupted. 

 Battery charger with LM317 Circuit Diagram


Battery charger with LM317 Circuit Diagram
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Diode less Rectifier Circuit Diagram

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Diode less Rectifier Circuit Diagram . It`s common knowledge that when working with single-supply op amps, implementing simple functions in a bipolar signal environment can be difficult. Sometimes additional op amps and other electronic components are required. Taking that into consideration, can any advantage be attained from this mode The answer lies in this simple circuit (A). Requiring no diodes, the circuit is a high-precision full-wave rectifier with a liigli-frequency limitation equalling that of the op amps themselves. Look at the circuit`s timing diagram (B) to see the principle of operation. The first amplifier rectifies negative input levels with an inverting gain of 2 and turns positive levels to zero .

The second amp, a noninverting summing amplifier, adds the inverted negative signal from the first amplifier to the original input signal. The net result is the traditional waveform produced by full-wave rectification. In spite of the limitation on the input signal amplitude (it must be less than VCCJZ), this circuit can be useful in a variety of setups.

 Diode less Rectifier Circuit Diagram


Diode less Rectifier Circuit Diagram
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Simple Intelligent Battery-Charging Circuit Diagram

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 Intelligent Battery-Charging Circuit Diagram . Intended for a Nicad application this charging circuit can be used with a wide range of batteries. A low-battery detector is intended. The trip voltage is set via the 500-kQ pot .
Select Rc for the battery you intend to use.

  Intelligent Battery-Charging Circuit Diagram


 Intelligent Battery-Charging Circuit Diagram
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Purpose Power Supply Circuit Diagram

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The Ppurpose Power Supply Circuit Diagram 6-66 can be used for supply output voltages from 1 to 35 V. The line transformer should be selected to give about1.4 times the desired output voltage from the positive side of filter capacitor C1 to ground. Potentiometer R2 sets the output voltage to the desired value by adjusting the reference input. Rsc is the current limit set resistor. Its value is calculated as: For example, if the maximum current output is to be 1 A, Rsc ~ 0.65/1.0 ~ 0.65 0. The 1-KO resistor, Rs, is a light-loaded resistor designed to improve the no-load stability of the supply.

 Purpose Power Supply Circuit Diagram


Ppurpose Power Supply Circuit Diagram
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Build a Low voltage regulators Circuit Diagram

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These Low voltage regulators Circuit Diagram short-circuit protected regulators give 6, 7, and 9 V from an automobile battery supply of 13 V nominal; however, they will function just as well if connected to a smoothed dc output from a transformer/rectifier circuit. Two types are shown for both positive and negative ground systems. The power transistors can be mounted on the heatsink without a mica insulating spacer thus allowing for greater cooling efficiency. Both circuits are protected against overload or short-circuits. The current cannot exceed 330 mA.

Under normal operating conditions the voltage across R2 does not rise above the 500 mV necessary to turn Q2 on and the circuit behaves as if there was only Q1 present. If excessive current is drawn, Q2 turns on and cuts off Ql, protecting the regulating transistor. The table gives the values of Rl for different zener voltages.

 Low voltage regulators Circuit Diagram

Low voltage regulators Circuit Diagram

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Simple Ni-cad charger Circuit Diagram

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Simple Ni-cad charger Circuit Diagram uses constant current LEDs to adjust charging current. It makes use of LEDs that pass a constant current of about 15 mA for an applied voltage range of 2-18 V. They can be paralleled to give any multiple of 15 mA and they light up when current is flowing.The circuit will charge a single cell at 15, 30 or 45 mA or cells in. series up to the rated supply voltage limit (about 14 V).

 Simple Ni-cad charger Circuit Diagram

Simple Ni-cad charger Circuit Diagram
 
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Simple Cold-Cathode Fluorescent-Lamp Supply Circuit Diagram

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Simple Cold-Cathode Fluorescent-Lamp Supply Circuit Diagram. For back-lit LCD displays, this supply will drive a lamp. LT1072 drives Ql and Q2, and a sine wave appears across CI. LI is a transformer that steps up this voltage to about 1400 V. Dl and D2 detect lamp current and form a feedback loop to the LT1072 to control lamp brightness. C1 = MUST BE A LOW LOSS CAPACITOR. METALIZED POLYCARB WIMA FPK 2 (GERMAN) RECOMMENDED. L1 = SUMIDA 6345-020 OR COILTRONIX CTX110092-1. PIN NUMBERS SHOWN FOR COILTRONIX UNIT. L2 = COILTRONIX CTX300-4 * = 1 % FILM RESISTOR. 

  Cold-Cathode Fluorescent-Lamp Supply Circuit Diagram


 Cold-Cathode Fluorescent-Lamp Supply Circuit Diagram
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