How Does an Automatic Door Work?

An automatic door works by using sensors or activation devices to detect when someone approaches. The sensor sends a signal to the door control unit, which activates the operator and motor to open the door safely. Safety sensors then help prevent the door from closing while someone is passing through.

Once the doorway is clear, the system closes the door at a controlled speed and returns to standby until it is activated again.

What are the main parts of an automatic door system?

An automatic door system is made up of several components working together. The exact setup will depend on the door type, building layout and how the entrance is used.

The main parts usually include:

Automatic door operator
The operator is the powered mechanism that opens and closes the door. It controls the movement of the door leaves and helps the door operate smoothly.

Control unit
The control unit is the central part of the system. It receives signals from sensors, push pads, access control systems or other activation devices, then tells the operator when to open, hold or close the door.

Motor and drive system
The motor provides the power needed to move the door. On sliding doors, this usually moves the door leaves along a track. On swing doors, the motor controls the opening and closing movement through the door operator.

Activation sensors
Activation sensors detect when someone is approaching the entrance. These may include motion sensors, presence sensors, touchless switches, push pads or access control devices.

Safety sensors
Safety sensors help prevent the door from closing on a person or object. They monitor the doorway and surrounding safety zones while the system is operating.

Door leaves, tracks and guides
The door leaves are the moving sections of the door. Sliding doors use tracks and guides, while swing doors use hinges, arms and operators. These components need to stay in good condition for reliable operation.

How do automatic door sensors work?

Automatic door sensors detect movement, presence or a signal from an activation device. Once triggered, the sensor sends information to the control unit, which activates the door.

Common automatic door sensors and activation methods include:

Motion sensors
Motion sensors detect movement near the entrance. They are commonly used in busy commercial environments where people need to enter and exit without touching the door.

Presence sensors
Presence sensors detect whether someone or something is within the doorway or safety zone. They help stop the door from closing while the opening is occupied.

Infrared sensors
Infrared sensors use light beams to detect presence or movement. They are often used as part of the safety system around automatic doors.

Microwave sensors
Microwave sensors detect movement and are commonly used to activate automatic sliding doors in shops, offices, hospitals and other high-footfall buildings.

Push pads and touchless switches
Push pads, elbow switches and touchless activation buttons can be used where controlled opening is preferred. They are often used for disabled access, staff entrances, healthcare areas and lower-traffic doors.

Access control systems
Automatic doors can also be linked with keypads, swipe cards, fobs, intercoms or building access systems. This is common in offices, education settings, healthcare facilities and restricted areas.

What happens when someone approaches an automatic door?

Although the system appears simple from the outside, several steps happen within seconds.

1. The sensor detects movement, presence or an activation signal. 
2. The control unit receives the signal. 
3. The automatic door operator activates the motor. 
4. The door opens at a controlled speed. 
5. The door remains open for a set hold-open time. 
6. Safety sensors check that the doorway is clear. 
7. The door closes safely and returns to standby. 

The hold-open time, opening speed and closing speed can usually be adjusted by a qualified engineer to suit the building, footfall and user needs.

What types of automatic doors are available?

Different buildings need different entrance systems. The right option depends on available space, traffic flow, accessibility requirements, security needs and how the entrance is used.

Automatic sliding doors
Automatic sliding doors are one of the most common options for commercial buildings. The door leaves slide to the side, making them suitable for busy entrances and areas where there may not be enough space for a swing door.

They are often used in hospitals, supermarkets, offices, universities, retail premises and public buildings.

Automatic swing doors
Automatic swing doors open inwards or outwards using a powered operator. They can often be installed on existing door sets, depending on the condition of the door, frame and surrounding structure.

They are commonly used for disabled access, internal doors, healthcare areas, corridors, offices and controlled access points.

Automatic folding doors
Automatic folding doors are useful where space is limited but a wider clear opening is still required. They can work well in narrow entrances or areas where a sliding system is not practical.

Automatic revolving doors
Automatic revolving doors help manage high levels of footfall while reducing draughts and heat loss. They are often found in large commercial buildings, hotels, offices and public entrances.

Low-energy automatic doors
Low-energy automatic doors operate at reduced speeds and forces. They are often used for accessibility improvements, especially where the door is activated by a push pad or access control system.

Access-controlled automatic doors
Automatic doors can be integrated with security systems, giving controlled access to staff, authorised visitors or specific areas of a building.

Are automatic doors safe?

Automatic doors are designed to operate safely when they are correctly specified, installed, commissioned and maintained.

Safety features may include activation sensors, presence detection, monitored safety zones, controlled opening and closing speeds, obstruction detection, emergency release functions and clear signage.

BS EN 16005 gives guidance on safety in use and test methods for powered pedestrian doorsets. The British Standards Institution describes BS EN 16005:2023 as giving practical advice on safety and best practice to help ensure powered pedestrian doors are installed with acceptable levels of user safety. 

Can existing manual doors be made automatic?

Whether an existing manual door can be automated depends on the door and its surroundings.

An engineer will usually assess the door construction, frame condition, hinge arrangement, available space, power supply, required clear opening width, access control requirements and overall safety needs.

For some sites, automating an existing door is a practical way to improve accessibility without replacing the full entrance. In other cases, a new automatic door system may be safer, more reliable or more suitable for long-term use.

Automatic door installation from Elite Entrance Systems

Automatic doors need to be specified around the building, not just the entrance opening. Footfall, access requirements, safety, security, user needs and long-term maintenance all need to be considered.

Elite Entrance Systems supplies, installs, repairs and maintains automatic entrance systems for commercial buildings across London, the South East and East of England.

Contact Elite Entrance Systems to discuss automatic door installation, repairs or maintenance contracts for your building’s automatic doors.

FAQs on Automatic Doors

How does an automatic door know when to open?

An automatic door knows when to open through sensors or activation devices. These may detect movement, presence, push-pad activation or an access control signal from a card, fob, keypad or intercom.

What sensors are used in automatic doors?

Automatic doors can use motion sensors, presence sensors, infrared sensors, microwave sensors, safety sensors, push pads, touchless switches and access control devices.

Can a manual door be made automatic?

Yes, some manual doors can be automated, but this depends on the door construction, frame, hinges, power supply, available space, access requirements and safety considerations. A site survey is usually needed before confirming the best option.

Are automatic doors suitable for commercial buildings?

Yes. Automatic doors are commonly used in offices, shops, hospitals, universities, public buildings, leisure centres and other commercial environments where access, safety and traffic flow are important.