Induction loop - Everything you need to know

Induction loops are a widely used technology for vehicle detection and access control and are used in many areas such as barriers, gates and traffic lights.

How an induction loop works

Induction loops work according to the principle of the electromagnetic field. A loop of wire is inserted into the ground and, together with a capacitor in the loop detector, forms an LC oscillator. A vehicle driving over the loop can be detected by the magnetic field generated by the loop. As soon as the vehicle enters the magnetic field, the inductance of the loop is changed, which leads to a change in the oscillator frequency. This frequency change is detected by the loop detector and used as a signal to control barriers, gates or traffic lights.

Application of the induction loop at barriers and traffic lights

Induction loops are often used in the control of barriers and traffic lights. In the case of barriers, the induction loop is installed in the entrance or exit to detect vehicles and automatically open or close the barrier. Traffic lights can also be controlled by induction loops to optimize traffic flow and reduce waiting times.

Construction and installation of induction loops

The construction of an induction loop is relatively simple, but requires precise work. The loop is usually laid in a square or rectangular shape and must be adjusted according to the size and number of turns. Typical loop sizes and the number of turns required are

• 3-6 m circumference: 5 turns
• 6-10 m circumference: 4 turns
• 10-20 m circumference: 3 turns
• 20-25 m circumference: 2 turns

When laying the induction loop, it is important to dimension the loop groove correctly and ensure that the loop strand is well insulated and mechanically protected. The loop should be laid at a distance of at least five centimetres from concrete reinforcements and one meter from moving metallic objects to avoid interference.

Induction loops for door control units

Induction loops are particularly useful for the control of gates as they offer a reliable and low-maintenance solution for vehicle detection. The loops are laid in the ground in front of the door and ensure that the door opens automatically as soon as a vehicle is detected. This increases safety and convenience for users and prevents unauthorized access.

Important notes on installation

There are a few important points to bear in mind when installing induction loops:

1. Cables for induction loops: Use high quality loop strands and make sure the insulation is intact to avoid short circuits.
2. Twisting of the supply lines: Lead wires should be twisted at least 20 times per meter to minimize electromagnetic interference.
3. Shielded supply lines: In areas with high electrical noise, shielded supply lines should be used.

Frequent problems and their solutions

Problems such as non-detection of vehicles or false alarms can occur if the loop is not installed correctly or the sensitivity of the detector is set incorrectly. It is important to measure the inductance of the loop before final installation and to size and route the loop correctly.

Induction loop: ideal for vehicle detection in door automation

The induction loop is an effective solution for vehicle detection at gates, barriers and traffic lights. With the right installation and maintenance, they offer a reliable and long-lasting option for access control and traffic management. By following the above advice and recommendations, the function and efficiency of induction loops can also be optimized.

Alternatives to induction loops

Depending on the installation conditions, the extensive work required to install an induction loop in the road surface can be an obstacle to the use of these product solutions. In such cases, a contactless sensor solution can be a good alternative. Possible alternatives to classic induction loops are: 

• the LZR H100 laser scanner for detection and security at barrier systems 
• the MWD-SBP barrier radar from FEIG or the Evoloop from BEA 
• a radar detector for object detection in front of the barrier 
• a light barrier installed above the driving area