The functions of magnetic switches in household appliances
1. Safety interlock
This is the most important function. For example, when the washing machine is in the spin-drying stage, if the upper cover is opened, it must immediately stop spinning to prevent injury. The common practice is: the upper cover is equipped with a magnet, and the body of the machine is equipped with a dry contact or Hall sensor. When the cover is closed, the magnet is close, the switch closes, and the computer board receives the “closed” signal, allowing the spin-drying to continue; when the cover is opened, the signal disappears, and the machine stops immediately.
The safety interlock in washing machines, microwave ovens, ovens, treadmills, etc. also have similar logic. The safety interlock generally needs to be “fail-safe”: if the magnet falls off or the sensor breaks, the system assumes that the door is not closed and does not allow dangerous actions.
2. Position detection
The cleaning robot detects whether the dust box and water tank are installed properly; the coffee machine detects the water tank; the air purifier detects the filter cover; the smart toilet detects the position of the cover plate. The magnet is installed on the detachable component, and the Hall or dry contact is installed on the main unit. When it is in place, it triggers.
3. Water level detection
Floats and magnetic rings are commonly used in water dispensers, humidifiers, and electric water heaters. The float moves up and down with the water level, and the magnetic ring approaches different heights of the dry contact, which then conducts or cuts off. The computer board uses this to determine high water level, low water level, and water shortage. When there is water shortage, the heating is cut off to prevent dry burning.
4. Flow and speed detection
In gas water heaters, water meters, and flow meters, the water flow pushes a magnetized rotor, and the Hall sensor outputs pulses, whose frequency corresponds to the flow rate. Fans and motors also use latch Hall sensors for speed measurement.
5. Door magnetic alarm
Magnetic and dry contact/Hall sensors are installed on refrigerator doors, windows, and cabinet doors. When the door is opened, the magnetic field disappears, and an alarm signal is output. Most door magnetic sensors in smart homes operate on this principle.
—
Typical household appliance cases
Washing machine: Upper cover magnet + reed switch / Hall sensor. It allows dehydration when closed, and stops immediately when opened.
Water dispenser / humidifier: Float magnet ring + reed switch. Heating is disconnected when water level is low, and water supply is stopped when water level is high.
Vacuum cleaner robot: Dust box, water tank, mop holder are equipped with magnets, and the main unit uses Hall sensor to detect whether they are installed.
Gas water heater: Water flow sensor uses Hall sensor, water flow drives the magnetic rotor, and outputs pulses, which are controlled by the computer board for ignition and gas ratio.
Refrigerator / intelligent door magnet: Door frame is equipped with reed switch, and the door body is equipped with magnet. Door opening triggers an alarm or lights up.
Microwave oven: Door interlock usually uses microswitch, not magnetic control switch; the “magnetic control tube” that generates microwaves is another matter.
Treadmill: Safety key often contains magnets, and removing it cuts off power and stops the machine.
Post time: Sep-16-2026