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Tag Archive: Hall Effect Switch

  1. What is a Hall Effect Sensor?

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    Hall Effect sensors are used for detecting and measuring proximity, position, and speed, through their ability to sense magnetic fields. As non-contact sensors, they are useful for measuring AC and DC currents. This blog will explain the principles behind Hall effect sensors and their industrial applications.

    What is a Hall Effect Sensor?

    magnetic switch designThe Hall Effect, named after its discoverer Edwin Hall, refers to the generation of voltage in a current-carrying conductor, perpendicular to the direction of the current flow, when the conductor is immersed in a magnetic field. A Hall Effect sensor is a thin piece of a conductor with current flowing along its length and a voltage detector connected across its width.

    When electric current traverses the sensor is in a magnetic field, the detector will register a small voltage. This voltage can be used to measure fluctuations in the magnetic field caused by changes in position, proximity, pressure, speed, temperature, or other factors.

    Since Hall Effect sensors do not have any moving parts, they are more robust and durable than reed switches. However, they are also more expensive since they need a constant electrical current flowing through them.

    Types of Hall Effect Sensors

    Hall Effect sensors are broadly divided into two categories: analog and digital. The analog sensors produce a continuously varying voltage output while the digital version has just two output voltages: high or low.

    Some of the sub-categories for Hall Effect switches include:

     

    Vane-operated

    These are digital proximity sensors that detect the presence or absence of a ferrous vane that passes through a gap between the two components of the vane-operated sensor: a permanent magnet and a Hall Effect sensor.

    Digital current

    This sensor also has two components in close proximity: a Hall Effect sensor and an electromagnet. The magnetic field produced by the electromagnet when current passes through its coils changes the output of the Hall Effect sensor.

    Linear current

    This is similar to the digital current sensor, except the output is analog.

    Closed-loop current

    Also called null balance current sensors, they work by nullifying the magnetic field being sensed by driving a current derived from the sensor output. Though they have excellent response, accuracy, and linearity characteristics, they are bulky and expensive due to the additional components required to generate the null balance current.

    Gear tooth

    As the name implies, these sensors detect the teeth of a gear as they pass by the sensor. Gear tooth sensors are similar to vane operated sensors but have additional circuitry to accurately measure speed. They are used in a variety of counting and speed sensing applications.

    Applications for Hall Effect Sensors

    As evident from the various categories of sensors mentioned above, Hall Effect sensors can be used for a wide range of applications, such as:

    • Automated product handling
    • CNC equipment
    • Compactors / Balers
    • Motion detectors
    • Position sensors (ex: doors)
    • Robotics (ex: limit switches)
    • Safety interlocks (ex: defeat resistant safety switches)

    Considerations for Hall Effect Sensor Design

    Hall Effect Sensor

    The important factors that influence the design of a Hall Effect sensor include:

    • Magnetic fields. The field produced by a magnet depends on its shape and size, the material used to construct it, the material in the path of the magnetic flux, and whether it is used as a unipolar or bipolar magnet.
    • Electrical considerations. What is the maximum current the sensor will have to handle? Is there a constant voltagesupply available to supply the sensor? What is the maximum flux it will experience? Should the output be analog or digital?
    • Operating environment. The temperature range over which the sensor must operate is an important environmental factor. Outdoor applications may require weatherproof housing for protection from rain and snow.
    • As with all industrial components, cost is an important issue with Hall Effect sensors. The operating temperature range, packaging requirements, precision and sensitivity of the output, and other features required by the application determine the final cost of the Hall Effect sensor.

     

    Hall Effect Sensors from MagneLink

    MagneLink has over 25 years of experience designing high-quality custom magnetic switches and sensors. Get in touch with us for all your Hall Effect magnetic switch requirements.

  2. Magnetic Switch Selection: Reed Switch vs. Hall Effect Switch

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    Reed switches and Hall Effect switches are both considered magnetic switches since their properties change when exposed to a magnetic field. Strictly speaking, however, Hall Effect switches are transducers since they convert magnetic energy to electrical energy—they can be used as switches with some additional circuitry. Reed switches are true magnetic switches since they close or open in the presence or absence of a magnetic field.

    Reed and Hall Effect switches are ubiquitous not only in electronic devices like cell phones and computers, but also in electromechanical systems like automobile control circuits and fluid control systems. System designers weigh many factors before considering Reed switches and Hall Effect switches for an application.

    reed switches vs hall effect switches

    Reed Switches

    Reed switches consist of a pair of contacts enclosed in a protective glass casing. The contacts are thin, flexible reeds made of ferromagnetic materials with a small air gap separating their contact points. When there is a strong enough magnetic field parallel to the reeds to magnetize them, they flex and touch to complete a circuit for current flow.

    Typically the magnetic field is generated by a permanent magnet, but a current carrying coil of wire may also be used. Unlike Hall Effect switches, Reed switches:

    • Do not need anything other than the magnetic field to bring about their switching action.
    • Are not sensitive to the polarity of the magnetic field.

    In other words, they will operate the same way for a North-South magnetic field as well as a South-North magnetic field as long as the magnetic field is parallel to the reeds.

    The hermetically sealed glass casing of a Reed switch protects it from mechanical shock and environmental factors such as dust, moisture, and corrosive gases. This makes Reed switches ideal for a wide variety of ambient conditions. Applications include:

    • Reed switches are safe for use in environments with explosive gases or chemicals because any sparking from the switching action stays within the glass case and switch housing encasing the reed switch.
    • They are widely used as speed sensors in bicycle wheels, car gears, and treadmills.
    • Reed switches serve as proximity sensors in electronic devices with a clamshell design, detecting whether the device is open or closed—flip phones and laptop computers are examples of such devices.
    • Applications that feature wide temperature ranges or harmful environmental factors.

    Hall Effect Switches

    reed switch vs hall effect switchHall Effect switches are semiconductor transducers that generate an electrical voltage when a magnetic field is present. The generated electrical voltage can be used for activating solid state switches. They require a constant flow of current to make them act as transducers.

    When a piece of Hall Effect material carrying an electric current is immersed in a magnetic field that is perpendicular to the current, several millivolts of electric potential develop in the material. The direction of the voltage is perpendicular to both the current and the magnetic field. As such, the polarity and direction of the current and magnetic field are crucial to the proper function of Hall Effect switches.

    Unlike Reed switches, Hall Effect switches:

    • Have no moving parts, so they are unaffected by mechanical shock.
    • Do not experience wear and tear either despite ‘switching’ at a high rate, even in excess of 100 kHz.
    • Can be protected from adverse environmental factors like dust and moisture through proper packaging.

    For all practical purposes, Hall Effect switches have an infinite life expectancy—with no mechanical components to wear out.

    Hall Effect switches are used for a variety of applications, such as:

    • Measuring the rotational speed of wheels and shafts.
    • Timing ignitions in internal combustion engines.
    • Tachometers and anti-lock braking systems.
    • Limit switches on actuators for automated controlled systems.

    Since they respond accurately and quickly to rapidly fluctuating magnetic fields, they are used for sensing the location of magnets in brushless DC motors.

    Magnetic Switches from Magnelink

    To summarize, both Reed switches and Hall Effect switches are activated by magnetic fields—the former as a classical switch and the latter as a transducer. Reed switches do not need any additional circuitry for switching, while Hall Effect switches do. There are significant differences between the two in sensitivity, switched load capacity, and life expectancy.

    Magnelink has been a supplier of reliable, high-quality magnetic switches at affordable prices for over 25 years. We specialize in providing standard and custom switches that meet our customer’s specific needs. Contact us today with your Reed switch vs. Hall Effect switch questions.