Why the barrier gate hit people? Right way to Install Car detector & Loop

According to Metropolis Daily, 'Ms. Li, who lives in Dongxihu, has been pregnant for more than 2 months. A few days ago, when Ms. Li was riding an electric motorcycle passing through a parking lot in Dongxihu District, the barrier of the parking lot suddenly dropped and just hit on her head, Ms. Li fell on the spot and eventually led to a miscarriage'.

According to Ms. Li’s recollection that when she rode an electric car to enter a parking lot in Yuquan District at noon that day, she saw that the non-motorized lane next to it was very narrow. At that time, the barrier of the parking lot was open, so Ms. Li rode an electric car into the parking lot. What she didn't expect was that as soon as she arrived at the entrance of the parking lot, the barrier was lowered and she gave her a head blow. The tragedy happened.

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<News from Metropolis Daily>

Speaking of smashing cars and people with the barriers of parking lots, many customers often judge the vehicle detector/ground sense as the culprit, so when the barriers are smashed, they blame the sense of ground.

Most people think that the ground sensor has the function of anti-smashing, and that the crashing of the car is caused by the crash, quality problems or damage of the ground sensor. actually not! The experience of parking lot accessories and systems such as the professional ground sense (vehicle inspection) of priority parking believes that the reason for the smashing of the car at the barrier is due to the improperly embedded detection coil!

Today we will justify the sense of place!

Many users don’t know that the real sense is essentially a switch. When a metal object moves on the detection coil, it will cause the inductance of the coil to change, which will cause the oscillation frequency to change; determine whether there is a vehicle by detecting the oscillation frequency change After passing, finally control the relay to close and open within the designed time.

The ground sense work must be signaled by the detection coil. It only plays a leading role. It is just a switch, which is only closed or opened within the designed time. Then the reason for the barriers to hit the car is basically revealed. The barriers to smash cars are basically caused by the detection coil, and the detection coil is buried by people, so in the final analysis it is a human accident.

So, what issues should be paid attention to during the burying process of the detection coil? Priority parking believes that the coils should be buried in accordance with the following specifications:

Vehicle detector (ground sense) coil construction specification

Whether the detector can work well depends largely on the induction coil it is connected to. Several important parameters of the coil include: coil material, coil shape and size, number of turns (inductance) and whether it is correctly constructed and buried. The following items must be noted during installation.

One: coil crosstalk

When the two induction coils are close together, the magnetic fields of the two coils are superimposed and interfere with each other. This phenomenon is crosstalk. Crosstalk can cause false detection results and deadlock of the loop detector. To eliminate crosstalk between adjacent coils belonging to different inductors, the following measures can be taken:

1. Choose different operating frequencies.

2. The number of turns of adjacent coils is different, and the spacing is increased. The distance between the detection coils must be greater than about 1 meter;

3. Perform good shielding on the lead wire of the coil, and the shielding wire must be grounded at the detector end. Coil cables and connectors are best to use multi-strand copper wires. It is best not to have a connection point between the cable and the connector. If you must have terminals, make sure the connection is reliable. Solder them with a soldering iron and place them in a waterproof place.

Priority parking license plate recognition machine

Two: coil material

Under ideal conditions (regardless of the influence of all environmental factors), the embedding of the inductor coil only considers the size (or circumference) and the number of turns, without considering the material of the wire. However, in actual engineering, the mechanical strength of the wire and the high and low temperature anti-aging issues must be considered, and the acid and alkali corrosion resistance must also be considered in some harsh environments.

Once the wire is aging or the tensile strength is not enough to cause the wire to be damaged, the detector will not work normally. In actual projects, it is recommended to use Teflon high-temperature silver-plated copper soft wires above 1.0mm or national standard cross-sectional area not less than 1.0-1.5 square millimeters multi-strand double-layer waterproof copper wire.

Detecting coil embedding specification

Three: coil shape

The width of the coil (the direction of the car is the width of the coil) determines the coil detection height (the height of the car chassis); that is, the coil detection height is 1/2 of the coil width. Therefore: the size of the vehicle models passed in different ground-sensing working environments; the shape and size of the embedded coils are different. Embed the coil according to the size of the passing vehicles on the road.

Note: the corners need to be chamfered

Four: Number of coil turns

In order to make the detector work in the best condition, the inductance of the coil should be kept between 100uH-300uH. When the inductance of the coil remains unchanged, the number of turns of the coil has an important relationship with the circumference. The smaller the circumference, the more turns. Generally refer to the following table:

As there may be various cable pipelines, steel bars, sewer covers and other metal materials buried under the road, these will have a great impact on the actual inductance of the coil, so the data in the above table is for user reference only. In the actual construction, the user should use the inductance tester to actually test the inductance value of the inductor coil to determine the actual number of turns in the construction, as long as the final inductance value of the coil is within a reasonable working range (such as between 100uH and 300uH).

Five: output lead

When winding the coil, leave a sufficient length of wire to connect to the loop inductor and ensure that there is no joint in the middle. After winding the coil cable, the lead cable must be made into a tightly twisted form, requiring at least 20 twists of 1 meter. Otherwise, untwisted output leads will introduce interference and make the coil inductance unstable. The output lead length should generally not exceed 5 meters. Since the sensitivity of the detection coil decreases with the increase of the lead length, the length of the lead cable should be as short as possible.

Six: Buried method

To embed the coil, first use a road cutter to cut grooves on the road surface. Chamfer the four corners with 45 degrees to prevent the sharp corners from damaging the coil cable. The groove width is generally 4 to 8 mm, and the depth is 30 to 50 mm. At the same time, cut a slot for the coil lead to the curb. But pay attention: the cutting groove must be clean and free of water or other liquids. When winding the coil, the coil must be straightened, but not too tight and close to the bottom of the groove. After the coil is wound, the output lead wire that has been twisted is led out through the lead slot.

In the winding process of the coil, an inductance tester should be used to actually test the inductance value of the inductance coil and ensure that the inductance value of the coil is between 100uH and 300uH. Otherwise, the number of turns of the coil should be adjusted.

After the coil is buried, in order to strengthen the protection, a nylon rope can be wound on the coil. Finally, seal the groove with asphalt or soft resin.

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