20-06-2012, 05:32 PM
ULTRASONIC MOTION SENSORS
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Introduction
A motion detector is an electronic device that detects the physical movement in a given area and transforms motion into an electric signal. The motion detector may be electrically connected to devices such as security, lighting, audio alarms, and the like. Motion sensors are used in a wide variety of applications and as a result many different types of motion sensors are available. Motion detectors are mainly used in for security systems. For example, motion detectors are typically positioned near exterior doorways or windows of a building for monitoring the area around the building. Upon detecting motion, they generate an electrical signal that is transmitted to a preselected audible alarm or lighting device which is then activated. A number of different technologies are used for motion detection. Motion detectors typically employ ultrasound, passive infrared (PIR), or radar detection techniques. Among the most used and most effective type of intrusion detection devices are the passive IR detectors which in recent years have replaced other types such as microwave or ultrasonic detectors.
TYPES OF SENSORS
Microwave sensors
Microwave sensors are used in large apartments since microwaves can penetrate through dielectric mediums. But they are generally not used because the unit consists of expensive super-high frequecy component whose radiations are not healthy for living organism
Infrared sensors
Infrared (IR) detectors are widely known in the arts of intrusion detection and in fire/smoke detection. These detectors have basically two forms: active and passive.
ACTIVE SENSORS
Active IR detectors include a radiation source and an IR sensor which is sensitive to interruptions in the radiation sensed from the source. These detectors are used as intrusion detectors by providing a path of radiation from the source to the sensor in a place where the path is likely to be interrupted by an intruder.
PASSIVE SENSORS
A passive infrared motion detection system detects heat energy radiated or emitted by an object, such as a body of a person, moving across a field of view of a heat sensor, such as a pyroelectric detector, of the motion detection system. Passive infrared motion detectors generally use an optical collection system and multiple sensing elements of alternating polarity to create a detection pattern in the volume of interest. Passive IR detectors generally employ a group of radiation sensors coupled through amplifiers to a logic circuit. PIR motion detectors are perhaps the most frequently used home security device.
Passive IR motion detectors are usually designed to provide an indication to an alarm panel in response to detecting IR that is indicative of motion of the object. The alarm panel is responsive to receipt of the breach indication to cause an alarm condition to occur. Infrared motion detector devices are often used in automatic light switches and security systems to turn on aA motion detector is an electronic device that detects the physical movement in a given area and transforms motion into an electric signal. The motion detector may be electrically connected to devices such as security, lighting, audio alarms, and the like. Motion sensors are used in a wide variety of applications and as a result many different types of motion sensors are available. Motion detectors are mainly used in for security systems. For example, motion detectors are typically positioned near exterior doorways or windows of a building for monitoring the area around the building. Upon detecting motion, they generate an electrical signal that is transmitted to a preselected audible alarm or lighting device which is then activated. A number of different technologies are used for motion detection. Motion detectors typically employ ultrasound, passive infrared (PIR), or radar detection techniques. Among the most used and most effective type of intrusion detection devices are the passive IR detectors which in recent years have replaced other types such as microwave or ultrasonic detectors.
Infrared (IR) detectors are widely known in the arts of intrusion detection and in fire/smoke detection. These detectors have basically two forms: active and passive.
Doppler shift motion detectors are active motion detectors in which a wave transmitter transmits waves into a monitoring area, and then a wave receiver receives the reflected waves and produces a reception signal. By detecting the Doppler shift in the reflected signal, the detector circuitry detects whether a moving object is present in the area. Typical applications include intruder alarms and automatic door openers, for which a unit of conventional construction comprises a gunn diode oscillator mounted in a cavity resonator such as a simple waveguide tube. However, Doppler radar-based motion detectors are disadvantageous because of limited materials penetration, microphonics, frequency crowding, and poor short-range operation.
Ultrasonic Movement Detector
Ultrasonic motion detectors project and receive ultrasonic sound energy in a region of interest. Object motion within the region of interest and in the range of the ultrasonic motion sensor is detected and an alarm signal representative thereof is produced. The effective range of ultrasonic motion detectors differs from design range whenever the actual ambient atmospheric sound propogation conditions vary from the design or nominal atmospheric conditions. Ultrasonic motion detectors are commonly used for automatic door openers and security alarms.
Ultrasonic motion sensors work on the principle of Doppler effect similar to radar or sonar.
DOPPLER EFFECT: It states that there will be an apparent change in frequency of signal with time when source and observer are in relative motion with respect to eachother
Ultrasonic sensor generates high frequency sound waves and evaluates the echo which is received back. Ultrasonic motion sensors are characterized by small power consumption,low cost,high sensitivity.These are commonly employed in office and home security.
TYPES OF ULTRASONIC SENSORS
Active sensors:Active sensors emit sound waves from the transducers and when there is any movement detected the sound waves get disturbed and activate any electrical or electronic control unit connected through relay.
Passive sensors
assive sensors operates on the principle of sounds such as breaking of glass or striking of metal.
These sounds produce waves which is detected by the sensor.These sensors offer very high sensitivity.
PRINCIPLE
There are two transducer:one emits an ultrasonic sound wave while the other picks up the reflection from the different objects in the area.The reflected waves arrive at the receiver in constant phase if none of the objects in the area are moving.If something moves,the received signal is shifted in phase.A phase comparator detects the shifted phase and sends a triggered pulse to the device connected to it through a relay.
Working Of Ultrasonic Movement Detector
The given figure shows the working of ultrasonic motion sensor.Basically there are two transducer:one emits an ultrasonic wave while other picks up the reflections.The reflected signal arrives in a constant phase if there is no motion in the area. If some motion is detected,the received signal is shifted in phase.A phase comparator detects the shifted phase and sends a triggering pulse to the relay which activates any device connected to it.
SPECIFICATIONS
Operating range:upto 4 mts.
Operating frequency:30-40 kHz
Power consumption:27mA
Sensor response time:0.25 secs
Port Explanation
Description
The UA741 is a high performance monolithicoperational amplifier constructed on a singlesilicon chip. It is intended for a wide range of analog applications.
The high gain and wide range of operatingvoltages provide superior performances inintegrator, summing amplifier and general
feedback applications. The internal compensation network (6 dB/octave) ensures stability in closed-loop cicuit.
Features
■ Large input voltage range
■ No latch-up
■ High gain
■ Short-circuit protection
■ No frequency compensation required
■ Same pin configuration as the UA709
Schematic Diagram
Applications
■ Summing amplifiers
■ Voltage followers
■ Integrators
■ Active filters
■ Function generators
IC HEF4093 BP:Quadruple 2 input NAND Schmitt Trigger
The HEF4093B consists of four Schmitt-trigger circuits.Each circuit functions as a two-input NAND gate withSchmitt-trigger action on both inputs. The gate switches atdifferent points for positive and negative-going signals.
The difference between the positive voltage (VP) and the
negative voltage (VN) is defined as hysteresis voltage
(VH)
Waveforms showing definition of
VP, VN and VH; where VN and VP are
between limits of 30% and 70%.
APPLICATION INFORMATION
:
• Wave and pulse shapers
• Astable multivibrators
• Monostable multivibrators
The HEF4093B used as a astable multivibrator
High Speed Diodes 1N4148
DESCRIPTION
The 1N4148 is a high-speed switching diode fabricated in planar technology, and encapsulated in hermetically sealed leaded glass SOD27 (DO-35) packages. The 1N4148 is designed for high-speed switching application in hybrid thick-and thin-film circuits. The devices is manufactured by the silicon epitaxial planar process and packed in plastic surface mount package.
FEATURES
•Hermetically sealed leaded glass SOD27 (DO-35) package
•High switching speed: max. 4 ns
•General application
•Continuous reverse voltage: max. 100 V
•Repetitive peak reverse voltage: max. 100 V
•Repetitive peak forward current: max. 450 mA
APPLICATIONS
•High-speed switching.
RESISTORS
A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current passing through it in accordance with Ohm's law:
The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.
The ohm (symbol: Ω) is a SI-driven unit of electrical resistance, named after Georg Simon Ohm. Commonly used multiples and submultiples in electrical and electronic usage are the milliohm (1x10−3), kilohm (1x103), and megohm (1x106).
Carbon composition resistors consist of a solid cylindrical resistive element with embedded wire leads or metal end caps to which the lead wires are attached. The body of the resistor is protected with paint or plastic. Early 20th-century carbon composition resistors had uninsulated bodies; the lead wires were wrapped around the ends of the resistance element rod and soldered. The completed resistor was painted for color coding of its value.
The resistive element is made from a mixture of finely ground (powdered) carbon and an insulating material (usually ceramic). A resin holds the mixture together. The resistance is determined by the ratio of the fill material (the powdered ceramic) to the carbon. Higher concentrations of carbon, a weak conductor, result in lower resistance. Carbon composition resistors were commonly used in the 1960s and earlier, but are not so popular for general use now as other types have better specifications, such as tolerance, voltage dependence, and stress (carbon composition resistors will change value when stressed with over-voltages). Moreover, if internal moisture content (from exposure for some length of time to a humid environment) is significant, soldering heat will create a non-reversible change in resistance value. These resistors, however, if never subjected to overvoltage nor overheating were remarkably reliable.
Thick film resistors became popular during the 1970s, and most SMD (surface mount device) resistors today are of this type. The principal difference between thin film and thick film resistors is not the actual thickness of the film, but rather how the film is applied to the cylinder (axial resistors) or the surface (SMD resistors).
Thin film resistors are made by sputtering (a method of vacuum deposition) the resistive material onto an insulating substrate. The film is then etched in a similar manner to the old (subtractive) process for making printed circuit boards; that is, the surface is coated with a photo-sensitive material, then covered by a pattern film, irradiated with ultraviolet light, and then the exposed photo-sensitive coating is developed, and underlying thin film is etched away.
Because the time during which the sputtering is performed can be controlled, the thickness of the thin film can be accurately controlled. The type of material is also usually different consisting of one or more ceramic (cermet) conductors such as tantalum nitride (TaN), ruthenium dioxide (RuO2), lead oxide (PbO), bismuth ruthenate (Bi2Ru2O7), nickel chromium (NiCr), and/or bismuth iridate (Bi2Ir2O7).
The resistance of both thin and thick film resistors after manufacture is not highly accurate; they are usually trimmed to an accurate value by abrasive or laser trimming. Thin film resistors are usually specified with tolerances of 0.1, 0.2, 0.5, or 1%, and with temperature coefficients of 5 to 25 ppm/K.
Thick film resistors may use the same conductive ceramics, but they are mixed with sintered (powdered) glass and some kind of liquid so that the composite can be screen-printed. This composite of glass and conductive ceramic (cermet) material is then fused (baked) in an oven at about 850 °C.
Thick film resistors, when first manufactured, had tolerances of 5%, but standard tolerances have improved to 2% or 1% in the last few decades. Temperature coefficients of thick film resistors are high, typically ±200 or ±250 ppm/K; a 40 kelvin (70 °F) temperature change can change the resistance by 1%.
Thin film resistors are usually far more expensive than thick film resistors. For example, SMD thin film resistors, with 0.5% tolerances, and with 25 ppm/K temperature coefficients, when bought in full size reel quantities, are about twice the cost of 1%, 250 ppm/K thick film resistors.
Wirewound resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core. The assembly is protected with a layer of paint, molded plastic, or an enamel coating baked at high temperature. Wire leads in low power wirewound resistors are usually between 0.6 and 0.8 mm in diameter and tinned for ease of soldering. For higher power wirewound resistors, either a ceramic outer case or an aluminum outer case on top of an insulating layer is used. The aluminum-cased types are designed to be attached to a heat sink to dissipate the heat; the rated power is dependent on being used with a suitable heat sink, e.g., a 50 W power rated resistor will overheat at a fraction of the power dissipation if not used with a heat sink. Large wirewound resistors may be rated for 1,000 watts or more.
Because wirewound resistors are coils they have more undesirable inductance than other types of resistor, although winding the wire in sections with alternately reversed direction can minimize inductance. Other techniques employ bifilar winding, or a flat thin former (to reduce cross-section area of the coil). For most demanding circuits resistors with Ayrton-Perry winding are used.
RESISTOR COLOUR CODE
Early resistors were made in more or less arbitrary round numbers; a series might have 100, 125, 150, 200, 300, etc. Resistors as manufactured are subject to a certain percentage tolerance, and it makes sense to manufacture values that correlate with the tolerance, so that the actual value of a resistor overlaps slightly with its neighbors. Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable.
In precision applications it is often necessary to minimize electronic noise. As dissipative elements, even ideal resistors will naturally produce a fluctuating "noise" voltage across their terminals. This Johnson–Nyquist noise is a fundamental noise source which depends only upon the temperature and resistance of the resistor, and is predicted by the fluctuation–dissipation theorem. For example, the gain in a simple (non-) inverting amplifier is set using a voltage divider. Noise considerations dictate that the smallest practical resistance should be used, since the Johnson–Nyquist noise voltage scales with resistance, and any resistor noise in the voltage divider will be impressed upon the amplifier's output.
In addition, small voltage differentials may appear on the resistors due to thermoelectric effect if their ends are not kept at the same temperature. The voltages appear in the junctions of the resistor leads with the circuit board and with the resistor body. Common metal film resistors show such an effect at a magnitude of about 20 µV/°C. Some carbon composition resistors can go as high as 400 µV/°C, and specially constructed resistors can go as low as 0.05 µV/°C. In applications where thermoelectric effects may become important, care has to be taken (for example) to mount the resistors horizontally to avoid temperature gradients and to mind the air flow over the board.[15]
Practical resistors frequently exhibit other, "non-fundamental", sources of noise, usually called "excess noise." Excess noise results in a "Noise Index" for a type of resistor. Excess Noise is due to current flow in the resistor and is specified as μV/V/decade - μV of noise per volt applied across the resistor per decade of frequency. The μV/V/decade value is frequently given in dB so that a resistor with a noise index of 0dB will exhibit 1 μV (rms) of excess noise for each volt across the resistor in each frequency decade. Excess noise is an example of 1/f noise. Thick-film and carbon composition resistors generate more noise than other types at low frequencies; wire-wound and thin-film resistors, though much more expensive, are often utilized for their better noise characteristics. Carbon composition resistors can exhibit a noise index of 0 dB while bulk metal foil resistors may have a noise index of -40 dB, usually making the excess noise of metal foil resistors insignificant.[16]
Thin film surface mount resistors typically have lower noise and better thermal stability than thick film surface mount resistors. However, the design engineer must read the data sheets for the family of devices to weigh the various device tradeoffs.
Like every part, resistors can fail in normal use. Thermal and mechanical stress, humidity, etc., can play a part. Carbon composition resistors and metal film resistors typically fail as open circuits. Carbon-film resistors may decrease or increase in resistance.[17] Carbon film and composition resistors can open if running close to their maximum dissipation. This is also possible but less likely with metal film and wirewound resistors. If not enclosed, wirewound resistors can corrode. The resistance of carbon composition resistors are prone to drift over time and are easily damaged by excessive heat in soldering (the binder evaporates). Variable resistors become electrically noisy as they wear.
All resistors can be destroyed, usually by going open-circuit, if subjected to excessive current due to failure of other components or accident.
CAPACITOR
A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When a potential difference (voltage) exists across the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the conductors. The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates.
An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.
A capacitor consists of two conductors separated by a non-conductive region.[7] The non-conductive substance is called the dielectric medium, although this may also mean a vacuum or a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from an external electric field. The conductors thus contain equal and opposite charges on their facing surfaces,[8] and the dielectric contains an electric field. The capacitor is a reasonably general model for electric fields within electric circuits.
Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt with by adding virtual components to the equivalent circuit of the capacitor. The usual methods of network analysis can then be applied. In other cases, such as with breakdown voltage, the effect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be dealt with separately. There is yet another group, which may be linear but invalidate the assumption in the analysis that capacitance is a constant
BREAKDOWN VOLTAGE
Above a particular electric field, known as the dielectric strength , the dielectric in a capacitor becomes conductive. The voltage at which this occurs is called the breakdown voltage of the device, and is given by the product of the dielectric strength and the separation between the conductorsThe maximum energy that can be stored safely in a capacitor is limited by the breakdown voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all capacitors made with a particular dielectric have approximately equal maximum energy density, to the extent that the dielectric dominates their volume.
For air dielectric capacitors the breakdown field strength is of the order 107 V/m and will be much less when other materials are used for the dielectric. The absolute breakdown voltage of most capacitors is nowhere near such a high number because of the very small distance between the plates. Typical ratings for capacitors used for general electronics applications range from a few volts to 100V or so. For high voltage applications physically much larger capacitors have to be used. In this field, there are a number of factors that can dramatically reduce the breakdown voltage below the value to be expected by considering the breakdown field strength of the dielectric alone. For one thing, the geometry of the capacitor conductive parts (plates and connecting wires) is important. In particular, sharp edges or points hugely increase the electric field strength at that point and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track" through the dielectric till it reaches the opposite plate and cause a short circuit.
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Introduction
A motion detector is an electronic device that detects the physical movement in a given area and transforms motion into an electric signal. The motion detector may be electrically connected to devices such as security, lighting, audio alarms, and the like. Motion sensors are used in a wide variety of applications and as a result many different types of motion sensors are available. Motion detectors are mainly used in for security systems. For example, motion detectors are typically positioned near exterior doorways or windows of a building for monitoring the area around the building. Upon detecting motion, they generate an electrical signal that is transmitted to a preselected audible alarm or lighting device which is then activated. A number of different technologies are used for motion detection. Motion detectors typically employ ultrasound, passive infrared (PIR), or radar detection techniques. Among the most used and most effective type of intrusion detection devices are the passive IR detectors which in recent years have replaced other types such as microwave or ultrasonic detectors.
TYPES OF SENSORS
Microwave sensors
Microwave sensors are used in large apartments since microwaves can penetrate through dielectric mediums. But they are generally not used because the unit consists of expensive super-high frequecy component whose radiations are not healthy for living organism
Infrared sensors
Infrared (IR) detectors are widely known in the arts of intrusion detection and in fire/smoke detection. These detectors have basically two forms: active and passive.
ACTIVE SENSORS
Active IR detectors include a radiation source and an IR sensor which is sensitive to interruptions in the radiation sensed from the source. These detectors are used as intrusion detectors by providing a path of radiation from the source to the sensor in a place where the path is likely to be interrupted by an intruder.
PASSIVE SENSORS
A passive infrared motion detection system detects heat energy radiated or emitted by an object, such as a body of a person, moving across a field of view of a heat sensor, such as a pyroelectric detector, of the motion detection system. Passive infrared motion detectors generally use an optical collection system and multiple sensing elements of alternating polarity to create a detection pattern in the volume of interest. Passive IR detectors generally employ a group of radiation sensors coupled through amplifiers to a logic circuit. PIR motion detectors are perhaps the most frequently used home security device.
Passive IR motion detectors are usually designed to provide an indication to an alarm panel in response to detecting IR that is indicative of motion of the object. The alarm panel is responsive to receipt of the breach indication to cause an alarm condition to occur. Infrared motion detector devices are often used in automatic light switches and security systems to turn on aA motion detector is an electronic device that detects the physical movement in a given area and transforms motion into an electric signal. The motion detector may be electrically connected to devices such as security, lighting, audio alarms, and the like. Motion sensors are used in a wide variety of applications and as a result many different types of motion sensors are available. Motion detectors are mainly used in for security systems. For example, motion detectors are typically positioned near exterior doorways or windows of a building for monitoring the area around the building. Upon detecting motion, they generate an electrical signal that is transmitted to a preselected audible alarm or lighting device which is then activated. A number of different technologies are used for motion detection. Motion detectors typically employ ultrasound, passive infrared (PIR), or radar detection techniques. Among the most used and most effective type of intrusion detection devices are the passive IR detectors which in recent years have replaced other types such as microwave or ultrasonic detectors.
Infrared (IR) detectors are widely known in the arts of intrusion detection and in fire/smoke detection. These detectors have basically two forms: active and passive.
Doppler shift motion detectors are active motion detectors in which a wave transmitter transmits waves into a monitoring area, and then a wave receiver receives the reflected waves and produces a reception signal. By detecting the Doppler shift in the reflected signal, the detector circuitry detects whether a moving object is present in the area. Typical applications include intruder alarms and automatic door openers, for which a unit of conventional construction comprises a gunn diode oscillator mounted in a cavity resonator such as a simple waveguide tube. However, Doppler radar-based motion detectors are disadvantageous because of limited materials penetration, microphonics, frequency crowding, and poor short-range operation.
Ultrasonic Movement Detector
Ultrasonic motion detectors project and receive ultrasonic sound energy in a region of interest. Object motion within the region of interest and in the range of the ultrasonic motion sensor is detected and an alarm signal representative thereof is produced. The effective range of ultrasonic motion detectors differs from design range whenever the actual ambient atmospheric sound propogation conditions vary from the design or nominal atmospheric conditions. Ultrasonic motion detectors are commonly used for automatic door openers and security alarms.
Ultrasonic motion sensors work on the principle of Doppler effect similar to radar or sonar.
DOPPLER EFFECT: It states that there will be an apparent change in frequency of signal with time when source and observer are in relative motion with respect to eachother
Ultrasonic sensor generates high frequency sound waves and evaluates the echo which is received back. Ultrasonic motion sensors are characterized by small power consumption,low cost,high sensitivity.These are commonly employed in office and home security.
TYPES OF ULTRASONIC SENSORS
Active sensors:Active sensors emit sound waves from the transducers and when there is any movement detected the sound waves get disturbed and activate any electrical or electronic control unit connected through relay.
Passive sensors
assive sensors operates on the principle of sounds such as breaking of glass or striking of metal.These sounds produce waves which is detected by the sensor.These sensors offer very high sensitivity.
PRINCIPLE
There are two transducer:one emits an ultrasonic sound wave while the other picks up the reflection from the different objects in the area.The reflected waves arrive at the receiver in constant phase if none of the objects in the area are moving.If something moves,the received signal is shifted in phase.A phase comparator detects the shifted phase and sends a triggered pulse to the device connected to it through a relay.
Working Of Ultrasonic Movement Detector
The given figure shows the working of ultrasonic motion sensor.Basically there are two transducer:one emits an ultrasonic wave while other picks up the reflections.The reflected signal arrives in a constant phase if there is no motion in the area. If some motion is detected,the received signal is shifted in phase.A phase comparator detects the shifted phase and sends a triggering pulse to the relay which activates any device connected to it.
SPECIFICATIONS
Operating range:upto 4 mts.
Operating frequency:30-40 kHz
Power consumption:27mA
Sensor response time:0.25 secs
Port Explanation
Description
The UA741 is a high performance monolithicoperational amplifier constructed on a singlesilicon chip. It is intended for a wide range of analog applications.
The high gain and wide range of operatingvoltages provide superior performances inintegrator, summing amplifier and general
feedback applications. The internal compensation network (6 dB/octave) ensures stability in closed-loop cicuit.
Features
■ Large input voltage range
■ No latch-up
■ High gain
■ Short-circuit protection
■ No frequency compensation required
■ Same pin configuration as the UA709
Schematic Diagram
Applications
■ Summing amplifiers
■ Voltage followers
■ Integrators
■ Active filters
■ Function generators
IC HEF4093 BP:Quadruple 2 input NAND Schmitt Trigger
The HEF4093B consists of four Schmitt-trigger circuits.Each circuit functions as a two-input NAND gate withSchmitt-trigger action on both inputs. The gate switches atdifferent points for positive and negative-going signals.
The difference between the positive voltage (VP) and the
negative voltage (VN) is defined as hysteresis voltage
(VH)
Waveforms showing definition of
VP, VN and VH; where VN and VP are
between limits of 30% and 70%.
APPLICATION INFORMATION
:
• Wave and pulse shapers
• Astable multivibrators
• Monostable multivibrators
The HEF4093B used as a astable multivibrator
High Speed Diodes 1N4148
DESCRIPTION
The 1N4148 is a high-speed switching diode fabricated in planar technology, and encapsulated in hermetically sealed leaded glass SOD27 (DO-35) packages. The 1N4148 is designed for high-speed switching application in hybrid thick-and thin-film circuits. The devices is manufactured by the silicon epitaxial planar process and packed in plastic surface mount package.
FEATURES
•Hermetically sealed leaded glass SOD27 (DO-35) package
•High switching speed: max. 4 ns
•General application
•Continuous reverse voltage: max. 100 V
•Repetitive peak reverse voltage: max. 100 V
•Repetitive peak forward current: max. 450 mA
APPLICATIONS
•High-speed switching.
RESISTORS
A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current passing through it in accordance with Ohm's law:
The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.
The ohm (symbol: Ω) is a SI-driven unit of electrical resistance, named after Georg Simon Ohm. Commonly used multiples and submultiples in electrical and electronic usage are the milliohm (1x10−3), kilohm (1x103), and megohm (1x106).
Carbon composition resistors consist of a solid cylindrical resistive element with embedded wire leads or metal end caps to which the lead wires are attached. The body of the resistor is protected with paint or plastic. Early 20th-century carbon composition resistors had uninsulated bodies; the lead wires were wrapped around the ends of the resistance element rod and soldered. The completed resistor was painted for color coding of its value.
The resistive element is made from a mixture of finely ground (powdered) carbon and an insulating material (usually ceramic). A resin holds the mixture together. The resistance is determined by the ratio of the fill material (the powdered ceramic) to the carbon. Higher concentrations of carbon, a weak conductor, result in lower resistance. Carbon composition resistors were commonly used in the 1960s and earlier, but are not so popular for general use now as other types have better specifications, such as tolerance, voltage dependence, and stress (carbon composition resistors will change value when stressed with over-voltages). Moreover, if internal moisture content (from exposure for some length of time to a humid environment) is significant, soldering heat will create a non-reversible change in resistance value. These resistors, however, if never subjected to overvoltage nor overheating were remarkably reliable.
Thick film resistors became popular during the 1970s, and most SMD (surface mount device) resistors today are of this type. The principal difference between thin film and thick film resistors is not the actual thickness of the film, but rather how the film is applied to the cylinder (axial resistors) or the surface (SMD resistors).
Thin film resistors are made by sputtering (a method of vacuum deposition) the resistive material onto an insulating substrate. The film is then etched in a similar manner to the old (subtractive) process for making printed circuit boards; that is, the surface is coated with a photo-sensitive material, then covered by a pattern film, irradiated with ultraviolet light, and then the exposed photo-sensitive coating is developed, and underlying thin film is etched away.
Because the time during which the sputtering is performed can be controlled, the thickness of the thin film can be accurately controlled. The type of material is also usually different consisting of one or more ceramic (cermet) conductors such as tantalum nitride (TaN), ruthenium dioxide (RuO2), lead oxide (PbO), bismuth ruthenate (Bi2Ru2O7), nickel chromium (NiCr), and/or bismuth iridate (Bi2Ir2O7).
The resistance of both thin and thick film resistors after manufacture is not highly accurate; they are usually trimmed to an accurate value by abrasive or laser trimming. Thin film resistors are usually specified with tolerances of 0.1, 0.2, 0.5, or 1%, and with temperature coefficients of 5 to 25 ppm/K.
Thick film resistors may use the same conductive ceramics, but they are mixed with sintered (powdered) glass and some kind of liquid so that the composite can be screen-printed. This composite of glass and conductive ceramic (cermet) material is then fused (baked) in an oven at about 850 °C.
Thick film resistors, when first manufactured, had tolerances of 5%, but standard tolerances have improved to 2% or 1% in the last few decades. Temperature coefficients of thick film resistors are high, typically ±200 or ±250 ppm/K; a 40 kelvin (70 °F) temperature change can change the resistance by 1%.
Thin film resistors are usually far more expensive than thick film resistors. For example, SMD thin film resistors, with 0.5% tolerances, and with 25 ppm/K temperature coefficients, when bought in full size reel quantities, are about twice the cost of 1%, 250 ppm/K thick film resistors.
Wirewound resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core. The assembly is protected with a layer of paint, molded plastic, or an enamel coating baked at high temperature. Wire leads in low power wirewound resistors are usually between 0.6 and 0.8 mm in diameter and tinned for ease of soldering. For higher power wirewound resistors, either a ceramic outer case or an aluminum outer case on top of an insulating layer is used. The aluminum-cased types are designed to be attached to a heat sink to dissipate the heat; the rated power is dependent on being used with a suitable heat sink, e.g., a 50 W power rated resistor will overheat at a fraction of the power dissipation if not used with a heat sink. Large wirewound resistors may be rated for 1,000 watts or more.
Because wirewound resistors are coils they have more undesirable inductance than other types of resistor, although winding the wire in sections with alternately reversed direction can minimize inductance. Other techniques employ bifilar winding, or a flat thin former (to reduce cross-section area of the coil). For most demanding circuits resistors with Ayrton-Perry winding are used.
RESISTOR COLOUR CODE
Early resistors were made in more or less arbitrary round numbers; a series might have 100, 125, 150, 200, 300, etc. Resistors as manufactured are subject to a certain percentage tolerance, and it makes sense to manufacture values that correlate with the tolerance, so that the actual value of a resistor overlaps slightly with its neighbors. Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable.
In precision applications it is often necessary to minimize electronic noise. As dissipative elements, even ideal resistors will naturally produce a fluctuating "noise" voltage across their terminals. This Johnson–Nyquist noise is a fundamental noise source which depends only upon the temperature and resistance of the resistor, and is predicted by the fluctuation–dissipation theorem. For example, the gain in a simple (non-) inverting amplifier is set using a voltage divider. Noise considerations dictate that the smallest practical resistance should be used, since the Johnson–Nyquist noise voltage scales with resistance, and any resistor noise in the voltage divider will be impressed upon the amplifier's output.
In addition, small voltage differentials may appear on the resistors due to thermoelectric effect if their ends are not kept at the same temperature. The voltages appear in the junctions of the resistor leads with the circuit board and with the resistor body. Common metal film resistors show such an effect at a magnitude of about 20 µV/°C. Some carbon composition resistors can go as high as 400 µV/°C, and specially constructed resistors can go as low as 0.05 µV/°C. In applications where thermoelectric effects may become important, care has to be taken (for example) to mount the resistors horizontally to avoid temperature gradients and to mind the air flow over the board.[15]
Practical resistors frequently exhibit other, "non-fundamental", sources of noise, usually called "excess noise." Excess noise results in a "Noise Index" for a type of resistor. Excess Noise is due to current flow in the resistor and is specified as μV/V/decade - μV of noise per volt applied across the resistor per decade of frequency. The μV/V/decade value is frequently given in dB so that a resistor with a noise index of 0dB will exhibit 1 μV (rms) of excess noise for each volt across the resistor in each frequency decade. Excess noise is an example of 1/f noise. Thick-film and carbon composition resistors generate more noise than other types at low frequencies; wire-wound and thin-film resistors, though much more expensive, are often utilized for their better noise characteristics. Carbon composition resistors can exhibit a noise index of 0 dB while bulk metal foil resistors may have a noise index of -40 dB, usually making the excess noise of metal foil resistors insignificant.[16]
Thin film surface mount resistors typically have lower noise and better thermal stability than thick film surface mount resistors. However, the design engineer must read the data sheets for the family of devices to weigh the various device tradeoffs.
Like every part, resistors can fail in normal use. Thermal and mechanical stress, humidity, etc., can play a part. Carbon composition resistors and metal film resistors typically fail as open circuits. Carbon-film resistors may decrease or increase in resistance.[17] Carbon film and composition resistors can open if running close to their maximum dissipation. This is also possible but less likely with metal film and wirewound resistors. If not enclosed, wirewound resistors can corrode. The resistance of carbon composition resistors are prone to drift over time and are easily damaged by excessive heat in soldering (the binder evaporates). Variable resistors become electrically noisy as they wear.
All resistors can be destroyed, usually by going open-circuit, if subjected to excessive current due to failure of other components or accident.
CAPACITOR
A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When a potential difference (voltage) exists across the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the conductors. The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates.
An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.
A capacitor consists of two conductors separated by a non-conductive region.[7] The non-conductive substance is called the dielectric medium, although this may also mean a vacuum or a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from an external electric field. The conductors thus contain equal and opposite charges on their facing surfaces,[8] and the dielectric contains an electric field. The capacitor is a reasonably general model for electric fields within electric circuits.
Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt with by adding virtual components to the equivalent circuit of the capacitor. The usual methods of network analysis can then be applied. In other cases, such as with breakdown voltage, the effect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be dealt with separately. There is yet another group, which may be linear but invalidate the assumption in the analysis that capacitance is a constant
BREAKDOWN VOLTAGE
Above a particular electric field, known as the dielectric strength , the dielectric in a capacitor becomes conductive. The voltage at which this occurs is called the breakdown voltage of the device, and is given by the product of the dielectric strength and the separation between the conductorsThe maximum energy that can be stored safely in a capacitor is limited by the breakdown voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all capacitors made with a particular dielectric have approximately equal maximum energy density, to the extent that the dielectric dominates their volume.
For air dielectric capacitors the breakdown field strength is of the order 107 V/m and will be much less when other materials are used for the dielectric. The absolute breakdown voltage of most capacitors is nowhere near such a high number because of the very small distance between the plates. Typical ratings for capacitors used for general electronics applications range from a few volts to 100V or so. For high voltage applications physically much larger capacitors have to be used. In this field, there are a number of factors that can dramatically reduce the breakdown voltage below the value to be expected by considering the breakdown field strength of the dielectric alone. For one thing, the geometry of the capacitor conductive parts (plates and connecting wires) is important. In particular, sharp edges or points hugely increase the electric field strength at that point and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track" through the dielectric till it reaches the opposite plate and cause a short circuit.