How Do Hall Effect Sensors Work? - The Learning Circuit

the following program is brought to you by element 14 the electronics community where you can connect and collaborate with top engineers from around the world join now at element14.com presents hi i'm karen and this is the learning circuit in previous videos we've learned about how magnetism can work together with electricity in various ways in this video we're going to learn about a sensor that outputs an electrical signal when it detects the presence of a magnetic field hall effect sensors in my video about electricity and magnetism we learned about magnetic fields flux density and polarity of both magnets and electric current electrons have magnetic fields therefore the flow of electrons electric current would also generate a magnetic field as electrical current flows magnetic field lines are generated perpendicular to the direction of flow the higher the amperage the stronger the magnetic force and the more flux in the magnetic field a higher flux density anything with a magnetic field has polarity a north pole and a south pole with flux lines connecting them like poles repel each other while unlike poles attract each other when we learned about motors we saw how current flowing through a coil creating an electromagnet can interact with a permanent magnet to create rotational movement and when we learned about microphones and speakers we saw that an electromagnetic coil can be made to move in and out around a permanent magnet by controlling the current running through it the rotational movement of the motor and the back and forth movement of the microphones and speakers are due to the polar interactions between the electromagnetic coil and the permanent magnet continuously attracting and repelling each other with those devices the magnetic fields interact and the permanent magnet causes the coil to move but what if the coil couldn't move as we've learned current flows in a straight line while generating an electromagnetic field in a hall effect sensor current flows through the device between its vcc and ground pins when an external magnetic field is introduced it interacts with the magnetic field of the flowing current the path of the current appears to curve as the electrons flowing through the device are deflected to one side creating a charge imbalance across the chip one side of the sensor has more electrons than the other creating a voltage potential difference across the sensor known as the hall voltage the stronger the magnetic fields the more the electrons within the hall effect sensor are deflected and the greater the voltage potential created this means that hall effect sensors cannot only detect if a magnetic field is present but also to what degree in an episode of element 14 presents i made this escape room puzzle that uses read switches read switches are electromechanical devices that activate in the presence of a strong enough magnetic field read switches are great but they are just switches they can only be open or closed hall effect sensors can have a more analog output detecting the strength of the magnetic field present here we have the inside of a hall effect sensor the hall chip is connected by wire leads to the two power terminals the two orange pieces are soft iron flux concentrators that help increase the sensitivity of the device as we learned in the electricity and magnetism episode iron has an extremely high relative permeability rating meaning it causes flux lines to bunch together tightly when a magnet is placed near the sensor the magnetic flux is concentrated and focused to flow through the hull chip around in a continuous loop producing either a positive or negative voltage exposed to the other pole of the magnet the sensor produces the opposite voltage within the hall effect sensor are amplifiers that further increase the intensity of the output signal hall effect sensors are available with either linear or digital outputs in digital output sensors after the amplifier the signal passes through a schmitt trigger before being output these have built-in hysteresis to prevent contact bounce digital sensors are bi-stable devices that can only be either on or off each has two preset values that show at what level of magnetic flux the device will switch to high or to low given these set thresholds a specific air gap distance can be determined for sensor activation linear or analog sensors have an output voltage that is directly proportional to the magnetic field passing through this sensor rather than having just an output state of on or off the output voltage can range from zero up to a saturation point determined by the power supply voltage hall effect sensors can also be either bipolar or unipolar unipolar sensors are like momentary switches turning on in the presence of one magnetic pole usually a positive south pole and will turn off when the magnet is removed these sensors are typically unaffected by the opposing negative north pole of the magnet bipolar sensors are like latching switches they turn on in the presence of one magnetic pole again usually south but when the magnetic pole is removed the sensor stays on only when the opposing north pole of a magnet is near will the sensor turn off again hall effect sensors are usually used in one of two sensing configurations with either the magnet approaching the sensor head on moving in and out or a sideways detection with the magnet moving left and right in front of the sensor head-on detection works as a proximity sensor varying the signal distance between a magnet and the sensor for either digital switching or linear analog signal detection a common application would be in a door and door frame detecting if it is open or closed with sideways detection you get a reading similar to the doppler effect the signal is weak as the magnet approaches gets strongest when directly in front of the sensor and the signal fades as the sideways movement continues sideways detection is used in motors we learned in our motor lesson that the coil wrapped rotors of a motor become electromagnets hall effect sensors can be placed near the outside of the rotor so that the end of each tooth passes along the face of the sensor notice how in both head-on and rotational positions the magnet pole is always pointing directly at the face of the sensor to ensure maximum sensitivity the flux lines should always be perpendicular with the magnet's pole where the flux is strongest pointing at the face of the sensor the output drive capabilities of hall effect sensors are very small so they cannot directly switch large electrical loads hall effect sensors are excellent for use in sensing position velocity and directional movement they are a popular choice of sensor because they are entirely electronic with no moving parts they do not require contact yielding wear free operation they are extremely low maintenance have a robust design and since they are sealed are immune to vibration dust and water don't forget you can find me on the element 14 community as maker karen so if you have any comments or questions post those on element14.com forward slash the learning circuit and keep an eye out for the follow-up video where i show how to use hall effect sensors in a project this one's actually going to be functional and useful i'm excited about it until then happy learning

Channel: element14 presents

Views: 19,753

Rating: 4.9653034 out of 5

Keywords: electronics, hardware, hacking, mods, weekly, element14, maker, engineering, element14presents, Hall voltage, Linear, Analog, Digital, Magnets, Polarity, Electromagnetism, Magnetic fields, Magnetic flux, Flux density, Schmidt trigger, Permeability, Lorentz force, Electric current, Air gap, Unipolar, Bipolar

Id: dgyB2-1VDI0

Length: 7min 56sec (476 seconds)

Published: Wed Apr 07 2021