If the Ground Induction Coil Is Embedded in the Parking Lot System?

The embedding of ground induction coil in parking lot system is very important, which can be said to be related to the safety and stability of the whole parking lot system. This article introduces the construction of ground induction coil from the principle of ground induction coil.1 Principle of vehicle detector and ground induction coil in parking lot1. Operating principle

Ground induction coil vehicle detector is a vehicle detector based on the principle of electromagnetic induction. It usually embeds a ring coil under the road subgrade of the same lane and supplies a certain operating current as a sensor.When the vehicle passes through the coil or stops on the coil, the iron on the vehicle itself will change the magnetic flux in the coil, resulting in the change of the inductance of the coil circuit. The detector will judge the state of passing vehicles by detecting the change of the inductance.There are generally two methods to detect the inductance change: one is to detect the phase change by using phase latch and phase comparator; The other is to use the coupling circuit composed of ring coil to detect its vibration frequency.

2. System compositionThe ground sensing vehicle detector includes ground sensing coil and detector. The coil is used as data collection. The detector is used to complete data judgment and output corresponding logic signals. The detector is generally composed of rack, CPU, detection card and wiring terminal.2 Effect of ground induction coil in parking lot system

In the parking lot system, to confirm the effect of the ground induction coil, we must first know the orientation of the ground induction coil device. The ground induction coil is generally installed in the following four orientations:1. Import ticket box (import control machine);2. One at the entrance and exit gates;

3. Exit ticket box (exit control machine);The ground induction coil used in the industry is generally copper core wire. People who have attended junior high school should know that when a metal object passes through the coil, an electric current will occur. This principle is used in the parking lot system.3 The ground feeling effect at the imported control machine can be located in two aspects:

1. Anti loss cardWe should all know that in the standardized one in one out system, temporary vehicles enter the site through automatic card collection. They only need to press the button. At this time, the effect of the ground feeling is that they can pick up the card when they sense that there is a vehicle there, rather than people can pick up the card by standing up and pressing the button.2. Ground pressure sensing card reader

In the remote card reading system (Bluetooth system, license plate recognition system), the local sense is used to distinguish the direction of vehicles.4 The effect of entrance and exit gate also has two aspects1. Anti smashing car. When there is a car at the ground feeling, the road gate rod will not fall off;

2. When the vehicle passes through the falling lever, the ground feeling at the exit controller is similar to that at the import controller. In the remote card reading system (Bluetooth system and license plate recognition system), the ground feeling is used to distinguish the direction of the vehicle.5 Precautions for grounding coil embedding

The "ground induction coil" in the parking lot system is a vibration circuit. It is constructed in this way. First, a circular groove with a diameter of about 1m or a rectangular groove with an equivalent area is made on the ground, and then two or three turns of wires are embedded in the groove, which forms an inductive coil buried on the ground. The coil is a part of a vibration circuit, which forms a vibration circuit with capacitors. Its principle is that the vibration is stable and reliable, The vibration signal is transformed and sent to the frequency measurement circuit composed of single chip microcomputer, and the single chip microcomputer can measure the frequency of the vibrator.

1 Coil materialIn the planning process, only the perimeter and turns of the ground induction coil are usually considered, and the material used is often ignored by planners. When the project is in its implementation stage, the mechanical strength and high temperature and aging resistance of the wire must be considered. In some harsh environments, the problem of acid-base corrosion must also be considered.However, in the practical application of conventional conductor, once the conductor is aged or the tensile strength is not enough, resulting in conductor damage, the detector will not work normally. Therefore, it is recommended to use teflon high temperature multi strand flexible conductor above 1.0mm.

2 Coil shape1. Rectangular deviceGenerally, the exploration coil should be rectangular. The two long sides are straight with the moving direction of the metal object, with an interval of 1m. The length of the long side depends on the width of the road, and the two ends are usually 0.3m to 1m narrower than the road interval.

3 Turns of coilIn order to make the detector work in the best condition, the inductance of the coil should be kept between 100uh-300uh. When the coil inductance is constant, the number of turns of the coil has an important relationship with the circumference. The smaller the perimeter, the more turns.Because various metal substances such as cable pipelines, steel bars and sewer covers may be buried along the way, which will have a great impact on the actual inductance value of the coil, the data in the above table are only for users' reference. During the actual construction, the user shall use the inductance tester to actually test the inductance value of the ground induction coil to confirm the actual number of turns during the construction, as long as the final inductance value of the coil is within a reasonable operating range (such as between 100uh-300uh).

4 Output leadWhen winding the coil, leave a wire of sufficient length to connect to the loop sensor and ensure that there is no connector in the middle. After winding the coil cable, the outgoing cable must be made into tight twisted pair, and it is required to be twisted for 20 times at least 1 meter. Otherwise, the output lead without twisted pair will introduce dry closing, making the coil inductance unstable.Generally, the length of output lead should not exceed 5m. Because the sensitivity of the exploration coil decreases with the addition of lead length, the length of lead cable should be as short as possible.

5 Embedding methodFor coil embedding, the road cutter shall be used to cut out the groove on the road surface. Chamfer the four corners 45 degrees to prevent sharp corners from damaging the coil cable. The cutting width is generally 4mm 8mm and the depth is 30mm 50mm. Together, cut a slot for the coil lead to the roadside.But pay attention: the 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 slot. After winding the coil, the twisted output lead shall be led out through the outgoing slot.

6 Precautions6.1 coil material: specification: 1.0 square high temperature resistant tinned wire.6.2 there shall not be many metals within 1m around, such as well cover, rainwater ditch cover, etc.

6.3 there shall be no power supply line exceeding 220V within 1m around.6.4 when making multiple coils, the interval between coils shall be greater than 2m, otherwise they will disturb each other.6.5 standardize the 3M wide road. The dimension of vehicle detector coil is 2m long and 1m wide. Chamfer 45 and 10cm long is made on the corner.

6.7 cutting parameters of buried trunking: the width is 4mm and the depth is 50-80mm. The depth and width shall be uniform, and the situation of sudden depth, shallow, width and narrow shall be prevented as far as possible.6.8 the coil shall be in the same balance orientation as the gate or the control machine.6.9 the two wires from the coil shall be twisted in pairs with a density of no less than 20 knots per meter. The output leads without twisted in pairs will cause disturbance. The length of output lead shall not exceed 5m. Because the sensitivity of the exploration coil decreases with the addition of lead length, the length of lead cable should be as short as possible.

6.10 after embedding, use cement, asphalt, epoxy resin and other materials to seal and solidify the notch. For cement pavement, the above three materials can be used. For asphalt stone pavement, asphalt or epoxy resin can be used. Pay attention to the coil when using asphalt pouring.