1. What exactly is a magnetic control switch?
Ordinary switches require manual pressing or mechanical lever manipulation. Magnetic control switches do not require direct contact; instead, they are triggered by magnetic fields. The most common two technical routes are:
1. Reed-type magnetic control switch: Two metal spring pieces inside a glass tube. When a magnet approaches, they are attracted and close; when the magnet moves away, they open. It does not require power supply on its own.
2. Hall-type magnetic control switch: Uses Hall elements or Hall ICs to sense the magnetic field and output an electrical signal, which then controls the circuit. It requires power supply, but has no mechanical contacts, has a long lifespan, and is easy to integrate with microcontrollers.
There are also magnetic resistance types, magnetic reed relays, etc., but in household appliances, the most common ones are reed and Hall types
II. Reed-type Magnetic Control Switch
1. Structure
A reed-type magnetic control switch is usually a sealed glass tube containing two ferromagnetic alloy reeds. The reeds serve as both the spring and the contact. The tube is generally filled with inert gas to prevent oxidation of the contacts. The pins are led out from both ends.
Some reed-type switches have two reeds, forming an open contact; some are made as a normally closed type by adding a bias magnet; others have a three-reed structure, making a switching type: one common terminal, one normally open terminal, and one normally closed terminal.
2. Principle
The reed-type switch itself does not have a magnet. When an external magnet approaches, the two reeds are magnetized, and the closer end forms opposite magnetic poles, thus attracting each other and closing the contact. When the magnet is removed, the magnetic field disappears, and the reeds separate by their own elasticity, and the contact opens.
If it is a normally closed type, there is a bias magnet inside or outside to keep the reeds closed; when the external magnetic field cancels the bias magnetic field, the contact actually opens. The switching type is like a single-pole double-throw switch, with the common terminal switching from the normally closed terminal to the normally open terminal.
3. Key Parameters
· Hitting value: Usually expressed in ampere-turns, reflecting the magnetic field strength required to close.
· Release value: When the magnetic field weakens to what extent it opens.
· The hitting value and release value are different, which is called hysteresis and can prevent jitter at the critical point.
· Contact capacity: The current and voltage it can handle. Reed-type switches generally can only handle small currents and cannot directly power motors or heating elements.
· Contact resistance, insulation resistance, withstand voltage, lifespan, and operating temperature should also be considered.
4. Advantages and Disadvantages
Advantages:
· No power supply required, the circuit is simple.
· Enclosed in a glass tube, it is dust-proof, moisture-proof and explosion-proof, suitable for humid environments such as washing machines and water dispensers.
· Non-contact triggering, without mechanical wear, long service life.
· Low cost, high reliability.
Disadvantages:
· The glass tube is fragile and prone to bending.
· The contact capacity is small. For heavy loads, relays, thyristors or MOS tubes need to be added.
· It is sensitive to strong magnetic interference.
· The attraction distance is limited, usually ranging from a few millimeters to a few centimeters.
· It performs worse than Hall effect in high-frequency operations.
III. Hall Magnetic Control Switch
1. Hall Effect
The Hall effect is: When current passes through a thin semiconductor sheet, if a magnetic field passes perpendicularly through the sheet, voltages will be generated on both sides of the sheet. This voltage is called Hall voltage. The stronger the magnetic field and the greater the current, the more obvious the voltage will be.
The Hall switch IC usually includes: Hall plate, amplifier, Schmitt trigger, voltage stabilizing circuit and output stage. It converts magnetic field changes into clean high and low levels.
2. Common Types
· Single-pole Hall: Responds only to one pole, such as the S pole, and releases when the magnet is removed.
· Bipolar Hall: The N pole and S pole are responsible for triggering and releasing respectively. This depends on the model.
· Latch Hall: Triggers the N pole and then remains locked until the S pole triggers again; then it releases. It is often used to measure rotational speed.
· Full-pole Hall: Either the N pole or the S pole can trigger, and it releases when the magnet is removed. This is commonly used in home appliance position detection and is easy to install.
Output forms include open drain, push-pull, NPN, PNP, etc. Open drain output usually requires an upper pull-up resistor to be connected to the microcontroller or driving circuit.
· Requires power supply and has static power consumption.
· Prone to static electricity, reverse connection, and voltage spikes.
· Strong magnetic fields, motors, transformers, and high-current wires may cause interference.
· The cost is usually higher than that of reed switches.
Post time: Sep-16-2026