US4881LUA Melexis Inc, US4881LUA Datasheet
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US4881LUA
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US4881LUA Summary of contents
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Section 3 - Applications 3 ...
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Section 3 - Applications Introduction Solid-state switches have been available for many years. In various applications, Hall- Effect Sensors (Hall ICs) have replaced mechanical contact switches completely. In the mid 1980’s the ignition points in automobiles were replaced by Hall ...
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The Hall-Effect The Hall-Effect principle is named for physicist Edwin Hall. In 1879 he discovered that when a conductor or semiconductor with current flowing in one direction was introduced perpendicular to a magnetic field a voltage could be measured at ...
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How Does it Work? A Hall IC switch is OFF with no magnetic field and ON in the presence of a magnetic field, as seen in Figure 1. The Earth’s field will not operate a Hall IC Switch, but a ...
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Activation - Using Hall-Effect Switches A switch requires a Hall IC, a magnet and a means of moving the magnet or the magnetic field. Figures 2, 3 and 4 show several ways by which a magnet can control the Hall ...
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Proximity Switch The proximity configuration is the simplest, though it requires the greatest amount of physical movement also less precise in terms of the position that results in turning the sensor ON and OFF. The magnetic field intensity ...
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An invisible or sealed switch may be made with either configuration. The Hall IC may be inside a sealed container to shield it from oil or water, while the magnetic field penetrates or “sees” through the sealed enclosure. Refer to ...
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Rotary Interrupt Switch The interrupt switch can be incorporated in applications of speed or position sensing, generally of rotat- ing objects. The Rotary Interrupt Switch, in Figure 6, uses a toothed ring to interrupt the magnetic field reaching the Hall ...
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Slide-by Switch R Figure 7, Rotary Slide-by Switch N S Figure 7A The Rotary Slide-by Switch in Figure 7 is generally used to measure rotary speed to synchronize switch- ing with position. The Hall IC is activated by a ...
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Working With Magnetic Fields How Do They Work? A magnetic field will convert electrical energy to mechanical energy, attract ferromagnetic objects and serves as an input for Hall-Effect Sensors. A magnetic field is described in terms of flux. Flux lines ...
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Evolution of Magnetics Modern society would not exist in its present form if not for the development of permanent magnet technology. Many of the major advances in the last century can be traced to the development of yet better grades ...
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The result is a shallow slope to the function curve. At some point, related to the material properties, increases in current through the magnetizing coil will not increase the value of the field ...
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This brings us once again the residual flux value, the pole orientation is now opposite the first satura- tion state. Finally reversing the current back to its original direction we can exercise the sample through the curve ...
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A magnet in a closed high permeability magnetic circuit (an iron bar connecting the north to the south pole) will operate at or near the Br value. A magnet with no pole pieces will operate with a flux density down ...
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Table 3, Magnetic Suppliers Company Name Address Arnold Engineering 300 North West St., Marengo Il Company 60152 Boxmag Magnets Chester St., Aston, Birmingham B6 4AJ, United Kingdom Crucible Magnetics 101 Magnet Drive, Elizabethtown, KY 42701 Dexter Magnetic Materials 48460 Kato ...
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Choosing A Magnet Common Magnetic Materials There are four classes of commercial permanent magnet materials. They are: Ceramic Alnico Neodymium Iron Boron Samarium Cobalt Depending on the application at hand, the use of one material over another may have its ...
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Rare-Earth Magnets Neodymium Iron Boron Attributes of Neodymium Low cost Very high resistance to demagnetization High energy for size Good in ambient temperature Material is corrosive and should be coated for long-term maximum energy output Low working temperature Applications of ...
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Alnico Magnets Attributes of Both Cast and Sintered Alnico (Large Magnets) Very stable, great for high temperature applications Maximum working temperature 524 May be ground to size Does not lend itself to conventional machining (hard & brittle) High residual induction ...
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Table 4, Magnetic Characteristics Magnetic Material Density 3 lbs/in g/cm SmCo 18 0.296 8.2 SmCo 20 0.296 8.2 SmCo 24 0.304 8.4 SmCo 26 0.304 8.4 Neodymium 27 0.267 7.4 Neodymium 27H 0.267 7.4 Neodymium 30 0.267 7.4 Neodymium 30H ...
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Magnetic Design Input Characteristics Digital Hall-Effect Sensors have specific magnetic response characteristics that govern their actuation from OFF to ON. These characteristics are classified in terms of operate point, release point and differ- ential. The operate point, commonly referred to ...
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Cost Hall IC cost will vary depending on the temperature specifications of BOP, BRP and Bhys. A loosely specified device may easily be one half to one third the cost of a tightly specified device, yet perform the same job. ...
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Graph 2, Slide-by Method with Magnet A Steep Slope vs. Shallow Slope 1200 1000 800 600 400 200 Distance (mm) Tolerances Build-up The following examples incorporate many different factors in order to show how ...
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Always "ON" 400 300 200 100 Air Gap = 2 mm Distance (mm) Air Gap = 3 mm Air Gap = 4 mm Graph 4, Slide-by With Magnet B, Steep Slope The ...
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Sample Magnet A is used in the double-pole slide-by method to show the variation air gap may have in a mechanical system. These changes in air gap may be caused by factors such as vibration, wear, etc... Note the differences ...
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Graph 8, Slide-by with Magnet A Change in Activation Distance With TC 400 300 200 100 0 -1 -0.75 -0.5 -0.25 0 0.25 -100 -200 -300 -400 Distance (mm) There is a 17% difference in flux density over the entire ...
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The Push-Pull Method Graph 10 shows the push-pull method. A South magnetic pole, perpendicular to the branded face, is used in conjunction with a North magnetic pole at the opposite face. The two magnets in the single-pole slide- by configuration ...
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Biased Operation Biased operation is a method of controlling the magnetic field surrounding a Hall IC and is quite similar to the Push-Push Method. For example South Pole were attached to the reverse side of a Hall Effect ...
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Flux Concentrators A flux concentrator, or pole piece ferrous material used to significantly increase the performance of a Hall Effect Sensor System. When a flux concentrator is placed opposite the pole face of a magnet, the magnetic field ...
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Electromagnets Another method of actuating Hall Effect Sensors is through the use of electromagnets. They are especial- ly useful in circuit-breaking or current-sensing applications because their magnetism can be “turned on” or “turned off” at will. An electromagnet consists of ...
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Measuring Flux Density The Melexis Hall-Effect design kit is supplied with a linear Hal-Effect sensor which has been calibrated to 1mV/G, making it very easy to build a circuit which will measure flux density. This is done with the fully ...
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Applications Balance, Level, Vibration, Acceleration A magnet suspended from a pendulum, free to move in the plane, may be used to detect level posi- tion, acceleration and vibration. Figure 12 shows a magnet with the center as ...
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Programmable Isolated Current Sensor Hall Effect Sensors can be used in conjunction with an electromagnet to make a very efficient, isolated current-sensing device. This can be used to protect components from damage such as overheating. The only components needed, as ...
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Flow Meter One popular device that uses a Hall flow meter (Figure 15). The spoked wheel (paddle wheel), is driven by some type of medium flowing through the pipe. A magnet is attached at the tip of ...
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Push-button The common push-button switch may be rep;aced with a Hall IC and magnet, as shown in two configu- rations, Figure 17. The slide-by case, Figure 17A, requires a mechanical return spring, returning the push button after it is depressed, ...
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Liquid Level Detector/Alarm By attaching a magnet to a float Figure 18, the proximity method of actuation is used to turn on the Hall IC as the liquid level rises within the housing. Figure 22, Liquid Level Detector ...
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Position Sensor As shown in Figure 19, a hydraulic or air-piston is moved downward until reaching the specified position set by the Hall IC. This could be a useful application in robotic assembly machines, where accuracy of position is extremely ...
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Geartooth Sensor Magnetic Geartooth Sensing The need to sense speed and position of ferrous gears occurs in numerous industries. The ability to con- vert the repetitive passing teeth to an electrical impulse has been sought for many decades. purely mechanical ...
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Gear Tooth Sensor Magnetics In order to detect the passing gear teeth with a Hall effect sensor it is necessary to provide a source of magnetic energy. The simple way to do this is to arrange a permanent magnet such ...
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Brushless DC Motor Sensors The use of Hall Effect Sensors in DC motors eliminates the friction, electrical noise and power loss asso- ciated with other types of mechanical commutation, such as brushes. Hall ICs provide a long mainte- nance-free life ...
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Programmable Motion Sensors The use of Hall-Effect Sensors as an alternative to resistive potentiometers is a popular trend because of the advantages of non-contacting elements. in the past, linear Hall ICs were not very practical because of bad temperature prformance ...
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The use of Hall Effect Sensors in DC motors eliminates the friction, electrical noise and power loss asso- ciated with other types of mechanical commutation, such as brushes. Hall ICs provide a long mainte- nance-free life and offer greater flexibility ...
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Other Applications Some additional Hall Effect Sensor applications are listed below: Application: Aircraft/Automotive: Tachometer Speed Indicator Roll Indicator Planing Angle Indicator Acceleration Indicator, Linear Fuel or Liquid-Level Sensor Seat Belt Sensor Airbag Ejection Sensor Power Window Sensor Door-Ajar Sensor Appliances: ...
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The Programmable Sensor Interface A microcontroller sensor interface provides signal conditioning for a sensor element of any kind. Some types of sensor elements that can be used are pressure sensors, strain gauges, load cells, thermistors, and potentiometers (position sensing). The ...
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Current Mode, which allows the user a 4mA to 20mA current range to use as a Hall Plate 2-wire analog sensor. These wiring examples as well as technical specifications are shown in section 4 of this book. Figure ...
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Microcontroller Family Overview Melexis is offering custom and semi-custom microcontrollers for automotive applications. Custom microcon- trollers provide the most cost affective solution by exactly matching the designers needs. Off-the-shelf micro- controllers typically force the customer to pay for features they ...
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Analog Interfaces There is a wide range of analog interfaces that can be integrated with the microcontroller. Multi-channel A/D converters in both 8 and 10 bit resolution . Band gap references for absolute measurements. On chip tempera- ture sensing for ...