Installation method for parking lot management vehicles

    Installation of basement

The ground sensing coil of the vehicle detector is an important component in the parking lot management system, and its working stability directly affects the operational stability of the entire system. Therefore, the production of the ground sensing coil is a very important part of the engineering installation process. Before making a ground sensing coil, the following points should be considered:

⑴ Coil material

In ideal conditions (without considering the influence of all environmental factors), the burial of inductance coils only considers the size (or circumference) of the area and the number of turns, and may not consider the material of the wires. However, in practical engineering, the mechanical strength and high and low temperature aging resistance of wire and conductor must be considered, and the acid and alkali corrosion resistance must also be considered in some places where the environment is harsh.
If the wire is damaged due to aging or insufficient tensile strength, the detector will not function properly. In practical engineering, it is recommended to use Teflon high-temperature flexible wires with a diameter of 1.0mm or more.

(2) Coil shape

① Rectangular installation

Usually, the detection coil should be rectangular. The two long edges are perpendicular to the direction of movement of the metal object, and the recommended distance between them is 1 meter. The length of the long side depends on the width of the road, usually 0.3 to 1 meter narrower than the distance between the two ends of the road.

② Installation tilted at 45 °
In some cases, when detecting bicycles or motorcycles, it is possible to consider installing the coil at a 45 ° angle to the direction of travel.

③ "8" shaped installation

In some cases, when the road surface is wide (more than six meters) and the vehicle's chassis is too high, this installation form can be used to disperse detection points and improve sensitivity.
This installation form can also be used for detecting sliding doors, but the coil must be close to the sliding door.

(3) The number of turns of the coil
In order to ensure that the detector operates at its optimal state, the inductance of the coil should be maintained between 100uH and 300uH. The number of turns and circumference of a coil have an important relationship when the inductance of the coil remains constant. The smaller the circumference, the more turns there are. Generally, the following table can be referred to:
Due to the possibility of various metal materials such as cable pipelines, steel bars, and sewer covers buried under the road, these can have a significant impact on the actual inductance value of the coil. Therefore, the data in the above table is for user reference only. During actual construction, users should use an inductance tester to test the inductance value of the inductor coil to determine the actual number of turns during construction, as long as the final inductance value of the coil is within a reasonable working range (such as between 100uH and 300uH).


  (4) Output lead

When winding the coil, it is necessary to leave enough length of wire to connect to the loop sensor, while ensuring that there are no joints in the middle. After winding the coil cable, the outgoing cable must be made into a tightly twisted pair, with a minimum of 20 twists per meter. Otherwise, untwisted output leads will introduce interference and make the coil inductance value unstable. The length of the output lead should generally not exceed 5 meters. As the sensitivity of the detection coil decreases with the increase of lead length, the length of the lead cable should be as short as possible.

(5) Embedding method

The first step in burying coils is to use a road cutter to cut grooves on the road surface. Perform a 45 degree chamfer on the four corners to prevent sharp corners from damaging the coil cable. The groove width is generally 4 to 8 millimeters and the depth is 30 to 50 millimeters. At the same time, it is necessary to cut a groove for the coil lead that leads to the roadside. But it should be noted that the groove must be clean and free of water or other liquids infiltrating. When winding the coil, the coil must be straightened, but not too tight and tightly attached to the bottom of the slot. After winding the coil, lead out the twisted output lead through the lead out slot.
During the winding process of the coil, an inductance tester should be used to actually test the inductance value of the 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 burying the coil, in order to strengthen protection, a nylon rope can be wrapped around the coil. Finally, seal the groove with asphalt or soft resin.

(6) Sealing material

The sealing of cable trays is generally done with hot melt asphalt, sealant, or epoxy resin. The main standard for cable tray sealing is to ensure that the coil cables are completely sealed and there are no bubbles inside. To ensure a long lifespan, it is recommended that all coil cables be completely sealed in resin, but this method cannot be used when the trunking or cables are wet.

Special precautions:

1. Loose buried wire of the coil: When the local sensing coil cannot be firmly fixed in the slot, the vibration of the car pressing over the road can cause deformation of the coil in the slot, changing the initial inductance of the ground sensing. At this time, the sensor must be reset before it can work normally, resulting in the failure of the vehicle detector detection. The solution is to pour the melted asphalt inside to fix it in place.
2. It is best to have an LC inductance measuring instrument to measure the size of the ground inductance of the ground induction coil, to confirm the number of turns of the ground induction coil and ensure that the inductance value of the coil is between 100uH and 300uH (about 180 uH is the safest), so that the vehicle detector can work stably within its range of use.
3. The ground sensing wire must not damage the protective layer. Use a digital meter to measure the ground resistance to be greater than or equal to 10M Ω, and the DC resistance to be 4-6 Ω; The ground sensing wire must not damage the protective layer. Use a digital meter to measure the ground resistance to be greater than or equal to 10M Ω, and the DC resistance to be 4-6 Ω;
5. There should be no large amount of metal within a range of 50 centimeters around, such as manhole covers, rainwater ditch covers, etc.
6. There should be no power supply lines exceeding 220V within a 1-meter radius.
7. When making multiple coils, the distance between the coils should be greater than 2 meters, otherwise they will interfere with each other.
8. Make a 45 degree chamfer on the four corners and polish it smooth to prevent sharp corners from damaging the coil cable.
9. The length of the cable should be calculated in advance and sufficient margin should be reserved (including coil lead out). It is strictly prohibited to have intermediate joints in the middle of the coil laying, and the cable should not have any skin or breakage
10. The routing should be as close as possible to the bottom of the slot, and the cables should be arranged in an orderly manner without crossing or overlapping
11. The lead wire from the coil to the ground sensing processor should be twisted at a rate of 20 cycles per meter, and the distance between the lead wire and the ground sensing processor should be as short as possible (if the lead wire at this end is too long, it will cause a decrease in ground sensing sensitivity). It is recommended that this section be within 1 meter and not exceed 5 meters at most.