The short answer
An automatic gate works by a motor driving the gate open and closed on a command from a remote, keypad, intercom or app, with a control board managing the movement and safety sensors — photocells and safety edges — stopping or reversing the gate if anything is in the way. Swing gates use underground or ram-arm motors; sliding gates use a rack-and-pinion motor on a track or cantilever. The safety sensors are not optional: automated gates are machinery and must detect and prevent crushing or entrapment. See our safety regulations guide for why.
An automatic gate looks simple from the outside — you press a button and it opens — but it is a small machine with several parts working together, including the safety devices that the law requires. Understanding the components helps you read a quote, ask the right questions, and appreciate why a properly specified gate costs more than a bare motor kit. This guide explains each part in turn, from the motors that move the gate to the sensors that keep people safe.
The main components
- Motors — drive the gate open and closed
- Control board — the ‘brain’ managing movement
- Power supply — mains spur, or solar/battery
- Safety sensors — photocells and safety edges
- Access control — remote, keypad, intercom, app
- Manual release — opens the gate in a power cut
The motors that move the gate
The motor is what physically drives the gate. For swing gates there are two common types: underground motors, buried in a drained pit at the hinge so the mechanism is hidden, and articulated ram arms, mounted on the pillars and visible but easier to retrofit. For sliding gates, a rack-and-pinion motor engages a toothed rack along the bottom of the gate and drives it along its track or cantilever beam. The motor must be sized to the weight and width of the gate — heavier timber or wrought-iron gates need stronger motors, as our materials comparison explains. Most domestic motors run on low-voltage DC, which is safer and allows battery back-up, with a transformer in the control box stepping the mains supply down.
The control board: the gate’s brain
The control board, housed in a weatherproof box near the gate, is the brain of the system. It receives commands from the access control, tells the motor to open or close, manages timing (such as an auto-close delay), and — critically — monitors the safety sensors and the motor’s force. Modern boards include obstacle detection: if the gate meets unexpected resistance, the board stops or reverses it. The board also sets the gate’s force limits, which an installer adjusts and then verifies by force testing to BS EN 12453. This is why the control board is not just a switch — it is part of the safety system.
The safety sensors that protect people
The safety sensors are the most important part of an automatic gate and the reason it is treated as machinery. Photocells project an infrared beam across the gate’s path; if anything breaks the beam while the gate is closing, the gate stops or reverses. Safety edges are pressure-sensitive strips along the leading and, where needed, trailing edges of the gate that trigger an immediate stop or reverse on contact. Together with correct geometry (designing out crushing and shearing points) and the control board’s force limiting, these prevent the gate from crushing or trapping a person, child or pet. There have been fatal accidents in the UK with gates lacking these devices, which is why a compliant installation always includes them — see our safety regulations guide.
| Component | Job | Why it matters |
|---|---|---|
| Motor | Drives the gate | Must be sized to gate weight |
| Control board | Manages movement & force | Sets and limits safety force |
| Photocells | Detect objects in the path | Stop/reverse on a broken beam |
| Safety edges | Detect contact | Stop/reverse on touch |
| Manual release | Opens gate by hand | Essential in a power cut |
Access control: how you open the gate
Access control is how you and visitors tell the gate to open. The simplest is a handheld remote fob; beyond that, a keypad lets you enter a code, an intercom (audio or video) lets visitors call the house and be let in remotely, a vehicle loop buried in the driveway detects a car to open the gate to leave, and a smartphone app allows control and entry from anywhere. Most homes combine a few of these — for example a fob for the household, a keypad or intercom for visitors. Our access control guide covers the options and their costs in detail.
Power and back-up
Automatic gates need a power supply, usually a mains spur run to the gate by an electrician, sometimes with an armoured cable ducted under the driveway. Because most domestic motors run on low-voltage DC, the system can include a battery back-up so the gate keeps working briefly in a power cut, and some sites use solar charging where running mains is impractical. Our power supply guide and solar and battery guide explain the options and when each makes sense.
Compare electric gate quotes
A good quote specifies the motors, control board, safety sensors and access control. Use our service to get matched with an automated gate installer who will explain the system for your site.
Frequently asked questions
How does an automatic gate know to stop if something is in the way?
Safety sensors do this. Photocells project an infrared beam across the gate’s path and stop or reverse the gate if the beam is broken; safety edges are pressure strips that stop or reverse the gate on contact. The control board also limits the motor’s force so the gate stops if it meets unexpected resistance.
What happens to an automatic gate in a power cut?
Every automatic gate has a manual release that lets you disengage the motor and open the gate by hand. Many systems also include a battery back-up so the gate keeps working for a while during an outage. Knowing where the release key is kept is important, including for emergency access.
What kind of motor does an automatic gate use?
Swing gates use either underground motors hidden at the hinge or articulated ram arms on the pillars. Sliding gates use a rack-and-pinion motor that engages a toothed rack along the gate. The motor must be sized to the gate’s weight and width — heavier gates need stronger motors.
Do I need photocells and safety edges on a domestic gate?
Yes, where the risk assessment requires them — which it almost always does for a powered gate that can crush or trap a person. Automated gates are machinery under the Supply of Machinery (Safety) Regulations 2008, and these devices are how the gate is made safe and passes force testing. A compliant installation includes them.
Sources & further reading
- DHF (Door & Hardware Federation) — how powered gates work and safe design
- Gate Safe — automated gate safety devices and awareness
- GOV.UK / HSE — Supply of Machinery (Safety) Regulations 2008 and powered gate safety
- BS EN 12453 / BS EN 13241 — safety in use of power-operated gates
This is general information, not advice for your specific property or installation. The components and safety devices needed depend on your gate and site. Automated gate work should be carried out by a competent installer who can demonstrate compliance with the safety regulations.