Have you ever pondered over how automated gate systems actually operate?

Automatic gates open and close with a simple press of a button on a remote transmitter. Others can be controlled from within the house through an intercom system installed at the gate, allowing communication with visitors.

But self-opening gates seem to work on their own as homeowners approach them while driving out.

These self-opening gates utilise specialised devices and controls to achieve exit control, and this article elucidates how this process unfolds. 

HOW DO ‘CONVENTIONAL’ AUTOMATIC GATES FUNCTION?

Automatic gates require motors to enable movement. They come with built-in control systems that instruct the motors on what actions to take and how to respond differently when receiving input from additional components in the system. These components can include safety devices to prevent contact with moving gates.

You can also command your automatic gates to open and close using radio signals sent when you press a button on a handheld remote transmitter. Alternatively, you may utilise access control intercoms to communicate with visitors at your driveway gates, allowing you to decide whether to grant them access or not.

HOW DO AUTOMATIC GATES AVOID COLLISIONS?

To ensure maximum safety during movement, automatic gate systems are designed with sensors to detect vehicles, pets, and people. Some of these safety sensors are integrated into the gate’s motors, while others are positioned on or near the gates.

If the gates encounter resistance during movement, certain gate motors with ‘obstacle detection’ functionality will halt their motion and reverse to allow the obstructing object to move to a safe distance.

Safety edges serve a similar purpose. These are rubber tubes mounted on walls and gates.

When the safety edge on a moving gate comes into contact with an object or person, the rubber compresses, completing an electrical circuit and sending a signal to the control panel to stop the gates and initiate a reverse movement.

Passive Photocells

Infra-red photocells function as safety sensors without requiring physical contact, unlike safety edges and obstacle detection. They are installed in pairs on either side of the protected areas. An active photocell is placed on one side of the driveway or danger zone, while its passive counterpart is mounted on the opposite side where the gates move through.

The active photocell emits an invisible beam towards its passive twin, which reflects it back. When anything moves between the two photocells, breaking the beam, the gate controls stop the gates’ movement before any collision occurs. Careful positioning of photocell pairs prevents anyone or anything from approaching the moving gates too closely.

This setup requires power only for the photocell that sends the beam to the passive reflector. As such, this type of photocell should be used exclusively for safety purposes, not for creating self-opening gates.

Active Photocells

Photocells with powered transmitter and receiver units can be used for both safety and egress control.

The transmitter can be wired or battery-powered, providing a range of 7 to 15 metres. The receiver unit always requires a power source via cable.

WHAT IS NEEDED TO ENABLE SELF-OPENING GATES?

Vehicle Detection

As a car approaches automated gates, something must recognise the vehicle and signal the gates to open. Many vehicle detection devices rely on electromagnetic induction.

When a car (or any large magnetic material) passes close to a device generating an electromagnetic field, it disrupts the field. This change in the electromagnetic field generates a signal sent to the gate control system, prompting the gates to open.

WHAT VEHICLE DETECTION DEVICES ARE USED IN SELF-OPENING GATES?

Active Photocells

A pair of active photocells can be used to create self-opening gates. These are installed on either side of the inside of the driveway, ensuring that the beam isn’t broken when the gates are open. As you approach the gates to leave, your car breaking the beam will trigger the gates to open automatically.

However, it’s essential to note that anything large enough to break the beam can also open the gates, making this solution less secure.

Inductive Loop

A loop of special cable is laid in a channel cut into the driveway, creating an electromagnetic field when current is applied. When a car enters this electromagnetic field, a signal is sent to the gate control.

Inductive loops can be used for safety and self-opening gates, but proper installation is crucial. The channels accommodating the cable must be 50mm deep and feature curved corners to avoid cable damage. Additionally, they must be over 1m away from other large metallic objects.

Once the channels are dug and the cable is in position, bitumen is filled in to protect the cable from damage and ensure waterproofing.

Magnetoresistive

Magnetoresistive systems operate similarly to loops, but they are much smaller. A channel is cut into the driveway for a single slimline detector and its cable. These detectors are small enough to be installed in pairs close to the automatic gates’ approach. They can also function as safety devices, with a maximum radius of 5ft.

Sensitivity settings allow fine-tuning to reduce interference and prevent false signals.

Other types of magnetoresistive detectors can be mounted by the side of the drive to provide an operating radius of up to 12 feet. However, cars must be moving at least 5 mph to be detected, making this system suitable only for egress control.

Additional technologies for vehicle detection use ultrasonic detectors or motion detection to identify metallic vehicles.

If the idea of gates opening magically as you approach to leave, while still providing security to keep unwanted visitors out, interests you, we can help.

Call us at 01420 552 463 or email sales@autogatepsr.co.uk to learn more.