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Conveyor belts are one of the widely used conveying devices in industries such as coal mines, metallurgy, and mining. During normal production, as materials are fed into transfer chutes using belt conveyors, scrapers, and other equipment, factors such as differences in particle size, shape, and flow velocity can easily lead to blockages in the chutes. This may result in equipment failures or mechanical accidents, including overload of the equipment, damage to the conveyor belts, and damage to the rollers. Traditional belt conveyor clogging protection devices use methods such as tilt switches, capacitive pressure sensors, rotary obstruction level switches, and fork-type level switches. However, these traditional methods exhibit numerous operational shortcomings in daily production, as follows: ① The working principle of an inclination switch is such that when it is subjected to external forces or deviates by an angle of more than 15–17 degrees from a horizontal position, the bead inside the switch tilts and rolls, changing its original state and altering the contact between the contacts, thereby changing the circuit state to output an on or off signal (from a normally closed state to an open state; from a normally open state to a closed state). The inclination switch may also tilt when impacted by materials, which can lead to incorrect operations. Additionally, since this type of switch is connected using cables, these cables are prone to breaking under the impact of materials, and as a result, this method is gradually being phased out ； ②The capacitive pressure sensor used for detecting blockages in the chute is installed on the side wall of the chute. Its working principle is that when its inner surface is compressed, the sensor activates, and the blocking device sends an alarm signal to the control room to shut down the equipment. However, in actual operation, this type of sensor is prone to being affected by impacts from the material, which can lead to false activations and subsequent shutdown of the equipment ； ③The anti-rotation level switch uses a micro motor as the driving mechanism; the drive shaft is connected to a clutch. When the switch’s blades are not in contact with the material, the motor operates normally. Once the blades come into contact with the material, the motor stops rotating, and the detection device sends out a signal to cut off the power supply and stop the motor’s operation. When the material descends, the resistance acting on the blades of the anti-rotation switch disappears, and the detection device returns to its original state thanks to the torsion spring. In practical use, a protective shield is often installed about 15 cm above the rotary switch; this approach helps to prevent wear on the switch caused by abrasive materials. However, after about half a year of use, dust carrying electricity can enter the switch due to sealing issues, leading to circuit board damage and thus product failure. Torque limit switches are generally suitable for light or powdered materials, but they are not very suitable for bulk ores or heavily loaded materials. Since the space in most chutes is limited, when dealing with large pieces of material, installing a baffle above the anti-rotation switch makes it more likely to occur accumulation and blockage of material ； However, if no protective device is installed, the anti-rotation switch will be damaged very quickly; high-quality products can last two to three months, while those of lower quality generally need to be replaced after about half a month. ④A tuning fork level switch causes the tuning fork to vibrate at a certain resonant frequency through a pair of piezoelectric crystals mounted on the tuning fork base. When the fork of the tuning fork level switch comes into contact with the medium being measured, its frequency and amplitude change. The intelligent circuit detects these changes, processes them, and converts them into a switch signal. Fork switches are suitable for applications involving fine powders, but if the external environment changes and causes the material to become humid, especially under the increasing environmental protection pressures, most factories use liquid spraying to control dust. This leads to the material accumulating on both sides of the fork switch, resulting in faulty operations. Moreover, when the conveyor transports lumpy material or heavy loads, if the material gets stuck on either side of the fork, it can also cause malfunction. The damage to switches caused by the mechanical wear and tear of materials on them is also a rather serious issue. As modern industry places increasing emphasis on intelligent manufacturing, it is an urgent need for various industrial and mining enterprises to select blockage detection switches that are reliable in performance and offer good cost-performance ratios. J-CONTROL is a Sino-foreign joint venture; its domestic subsidiary is Jike Industrial Control Systems (Tianjin) Co., Ltd. Based on years of research in Doppler radar sensors, the company has developed microwave barrier switches, which are non-contact level detectors particularly suitable for monitoring chutes carrying lump materials or heavy-duty substances. The application photos of J-CONTROL in a mining enterprise are shown below: The microwave barrier switch consists of a microwave transmitter and a microwave receiver, which are installed on either side of the silo at the same height and in corresponding positions. The signal emitted by the microwave transmitter can penetrate the wall panels with the help of mounting aids (materials with low dielectric constants such as rubber, nylon, PEEK, PTFE, ceramics, and refractory bricks), and is then received by the signal receiver. After receiving the signal, the microwave receiver determines whether there is material in the bin based on the presence or absence of the signal. Depending on the operating conditions and temperature, additional installation accessories such as heavy-duty or high-temperature insulation can be selected accordingly. The detection range for the horizontal level of the microwave barrier can reach 0~110m ； The microwave receiver features a 10-segment LED LCD display, which facilitates the adjustment of the reception strength, as shown in the figure below ； The transmitter and receiver feature a 4 communication channel selection function, which ensures that when installed at high, very high, low, and very low positions simultaneously, interference between the various communication channels is avoided, as shown in the figure below. The microwave barrier switch is capable of penetrating insulating materials such as glass, ceramics, and dry refractory bricks (materials with low dielectric constants); by taking advantage of this property of microwaves, it is possible to detect the level of material inside containers that have insulating walls ； The product is suitable for material handling conditions involving heavy loads, high temperatures, and high pressures ； The receiver features a demonstration adjustment function; via the delay knob, a delay setting within the range of 0 to 10 seconds can be achieved ； The microwave receiver features a function for adjusting the operating value of the receiver; through the LED display panel, different operating values can be set to suit various materials with different dielectric constants. Product Model and Parameters: Brand: J-CONTROL Name: Microwave Barrier Level Switch Model: JCMWS-TR3□□□/JCMWS-RC3□□□ Power Supply Voltage: 220V AC 50/60Hz (the transmitter and receiver must be of the same type) Power Consumption: Transmitter – Max. 3.6W; Receiver – Max. 4.9W Detection Range: Up to 110m (the detection range depends on the surrounding environment) Frequency: Approximately 24GHz Output Signal: SPDT contact output; contact rating: AC 250V 3A Operation Detection: ON when interrupted; ON/OFF DELAY: Delay between ON/OFF states when interruption lasts longer than the set time; ON/OFF DELAY: 0.1–10s (adjustable) Operating Temperature: -30–1200°C (depending on the mounting accessories used) Operating Pressure: Below ±0.5MPa (±5kgf/cm2) Materials: Housing – ADC; Probe – SUS304; Transmitter/Receiver surfaces – PEEK Mounting Method: G1 mounting screws (with fixing nuts and washers) Wire Exit: Transmitter: M20X1.5 (wire diameter: φ9–φ13mm); Receiver: M20X1.5 (wire diameter: φ9–φ13mm) Protection Rating: IP65