What should I do if the parking lot system vehicle barrier does not drop down?

The installation of the inductive loop coil in a parking lot system is crucial to ensure the stability and functionality of the entire system. This guide explains the construction process, beginning with the principle of the loop coil and its application in parking systems.

I. Principle of Vehicle Detectors and Inductive Loop Coils in Parking Systems

1. Working Principle

The inductive loop vehicle detector is based on the principle of electromagnetic induction. It typically consists of a loop of wire buried under the road surface, which acts as a sensor when a certain current passes through it.

When a vehicle passes over or stops on the loop, the iron components in the vehicle change the magnetic flux in the coil, altering the inductance of the loop. The detector uses these changes to determine the presence and status of the vehicle.

There are two main methods of detecting inductance changes:

• Phase Lock Loop (PLL) and Phase Comparator: These detect phase changes in the coil.
• Oscillating Circuit Method: The frequency of the oscillating circuit formed by the loop is used for detection.

2. System Components

An inductive vehicle detection system includes:

• Loop Coil: Responsible for data collection.
• Detector: Analyzes data and provides logical signals based on the vehicle's presence. The detector typically consists of a frame, a central processor, a detection card, and terminal connectors.

II. Function of Inductive Loop Coils in Parking Systems

To understand the role of loop coils, it’s essential to know their installation locations, typically at:

1. The entrance ticket box (entry control machine),
2. The entrance and exit barriers (one for each),
3. The exit ticket box (exit control machine).

The loop coil detects metallic objects such as vehicles, generating a current that is used by the parking system.

III. Functions at Entrance Control Machine

1. Card Prevention: In a standard parking system, temporary vehicles take an automatic ticket when entering. The loop coil ensures that only vehicles (not people) trigger the ticket dispenser.
   
2. Vehicle Direction Detection: In systems like Bluetooth or license plate recognition, the loop coil helps distinguish vehicle direction.
   

IV. Functions at Entrance and Exit Barriers

1. Anti-Vehicle Collision: When a vehicle is detected by the loop coil, the barrier will not lower, preventing damage to the vehicle.
   
2. Barrier Drop After Vehicle Passes: Similar to the entry control system, the loop coil at the exit helps detect vehicle direction in distance-based recognition systems.
   

V. Key Considerations for Inductive Loop Coil Installation

The inductive loop in a parking system forms part of an oscillating circuit. The following details the coil installation process:

1. Materials

In harsh environments, the durability of the coil wire is crucial. The wire should be able to withstand mechanical stress, high/low temperatures, and resist corrosion. Recommended wire: 1.0mm or thicker Teflon high-temperature multi-strand wire.

2. Shape of the Coil

The typical shape is rectangular. The long sides of the loop should be perpendicular to the direction of vehicle movement, with a spacing of 1 meter. The length depends on the width of the road, usually narrower by 0.3 to 1 meter compared to the road width.

3. Number of Turns

The inductance of the loop should range from 100uH to 300uH. The number of turns of the coil is related to its perimeter, with smaller perimeters requiring more turns. The actual inductance should be measured using an inductance tester to ensure it falls within the acceptable range (100uH-300uH).

Coil turns

For testing，circumference less than 0.5 meters

More than 25 turns

Below 3 meters

Not recommended

3-6 meters

5-6 turns

6-10 meters

4-5 turns

More than 10 meters

Not recommended

4. Output Leads

During installation, ensure the output leads are tightly twisted (20 twists per meter) to avoid electromagnetic interference. The length of the output lead should not exceed 5 meters as it affects sensitivity.

5. Burial Method

• Use a cutting machine to create a trench in the road surface (4-8mm wide and 30-50mm deep).
• Avoid water or other liquids in the trench.
• The loop must be laid flat and tightly in the trench.
• Lead-out wires should be routed through a separate trench.

6. Important Installation Guidelines

• Coil Material: Use 1.0mm² high-temperature tin-plated wire.
• Proximity to Metal: Avoid large metal objects like manhole covers within 1 meter.
• Proximity to Power Lines: Avoid high-voltage power lines within 1 meter.
• Coil Distance: Keep a minimum 2-meter distance between adjacent loops to prevent interference.
• Coil Size: For a standard 3-meter-wide road, the coil should measure 2 meters long and 1 meter wide, with corners beveled at 45°.

7. Trench Dimensions

The trench should be 4mm wide and 50-80mm deep, with uniform width and depth.

8. Seal and Finish

Once the loop is installed, seal the trench with cement, asphalt, or epoxy resin depending on the road surface material.