Mechanical Access Control Devices
♦ Mechanical Access Control Devices – Mechanical devices by their very nature rely on movement as compared with electronic devices that switch on change of state only. Mechanical devices also have to overcome other barriers such as friction, mass, momentum, spring tension, torque and other pressures.
Taking opposing forces to an extreme, consider motor-driven boom gates, rising steps and roller shutters, where opening and closing times may range from 3-20 seconds. To overcome these prolonged delays in access control systems, innovations and improvements constantly evolve in the areas of mechanical operation, electromechanical operation, electromagnetic operation, hydraulic and pneumatic systems.
Common mechanical systems include devices and instruments that are exclusively mechanical in operation and require only manual manipulation, such as locks, door handles, chain operated roller shutters and hand operated gates and boom gates.
These systems are a poor access control choice in anything other than basic operations, being time consuming to use and offering poor levels of security and no audit trails.
Under this heading fall most mechanically operated devices that derive their energy and mobility from DC or AC powered electric motors. Speed of opening and closing is usually increased, and remote operation can be incorporated. Application is found in lifts, escalators, automatically operated gates, rising steps, boom gates and automatic motor-driven roller shutters and sliding doors.
On average, electromagnetic devices are faster than electromechanical equipment, though in some areas their characteristics do overlap. These devices include relays, solenoids, electromagnets and magnetic reed contacts that are ideal for applications in electromechanical and electromagnetic locks, depending on the application used. These devices are ideal for bridging short distances because the movement of their locking component is usually limited to a mere 25-30mm in ideal circumstances.
Slow moving, hydraulic principles in access control are restricted to applications where speed is not essential, and force of movement is not important. Such a case would be where large and heavy boom gates or platforms need to be elevated or lowered.
As with hydraulic systems, pneumatics are generally only used where strong force is needed. Over very short distances, however, pneumatic action, which for practical purposes may also include the use of gas pressure, can be relatively fast. Pneumatic pressure has been used to operate specially designed locks at speeds under one second.
Prefer Electro Systems
Although far from perfect, electro motors, solenoids and relays are still preferred over non-electric systems. The chief task of electromechanical and electromagnetic devices is to convert electrical energy into mechanical movement. Such electrically operated devices are considered most suited for use in automated electronic access control systems
Although microprocessors and electronic circuits are not immune from failure, the majority of malfunctions that occur in access control systems relate to failure of mechanical devices. One of the biggest causes of physical malfunction is people.
Installers may put a vulnerable indoor access reader outdoors where metallic dust from a nearby foundry gets into the casing and causes short circuits. End users may use damaged and dirty cards, or failure to protect the reader from damage, while vandals may endeavour to smash the reader completely.
Devices that are subjected to severe environmental conditions should be weatherproof and able to withstand moisture, dust, extreme temperature and a reasonable level of rough handling. Choosing readers with potted electronics is a clever move. It’s worth bearing in mind that extreme temperatures will have an impact on all electronic circuits. They are stable between 0 and 60 degrees but outside these parameters, things can get wobbly.
Areas where there could be significant improvements in improving the device/user interface in access control systems include educating users how to operate and understand the system. It’s important users are able to use the system to fullest advantage while maintaining its integrity. Part of this process is establishing times and routes for incoming and outgoing traffic flow. It’s also vital that installers use the correct hardware when installing the system – that means compatible locks, striker plates and other peripherals.
Considerations of Door Hardware
Since the advent of access control few designers of doors and door hardware and designers of mechanical locking devices have developed products that have perfect compatibility with each other. The result of this is that it can be difficult to find an electric latch or a striker plate to suit the bolt or tongue of a mechanical lock, especially if the architect has specified key door components with a focus on aesthetics.
It’s just as difficult to find an electric locking mechanism that offers a degree of security commensurate with that offered by advanced electronic access control systems. The fact many door locks were never designed to be kept in check by an electric strike plate doesn’t make things any easier. The result can be high tech, high security access control and access management systems that may be worth hundreds of thousands of dollars inherently weakened by poor lock and door hardware door design.
Some of the access lock and door problems installers will face and security managers must look out for include:
* Bolt or tongue of the lock not extending far from lockcase
* Electric striker plate providing insufficient space for the entire lock bolt so bolt is only partly actuated
* Doors badly fitted into their frames
* Large tolerance between leading edge of the door and vertical upright of door frame.
The majority of striker plates, electric locks and mechanical locks used in conjunction with electric locking offer little resistance against forced entry. And there’s a further complication that makes securing sites harder – many turnstiles, gates, booms, doors and shutters have their own particular ways of operating. Some hinge, some slide, others turn or tilt. Yet others consist of more than one section – electrically locking and unlocking a set of double doors takes ingenuity and customisation.
Some of the locking options available from manufacturers include:
* Standard electric latch (or striker plate) either left or right-hand operation
* AC or DC latches for metal or wooden doors, for vertical mounting or horizontal mounting, offset, and recessed, with or without sensing contacts for flush fitting, or rim fitting
* Electric locks with round bolts or hook bolts
* Electric locks for all glass doors, turnstiles, gates and shutters
* Electromagnetic double-acting solenoid mortise deadlocks
* Electromagnetic locks
* High security prison locks and blast proof locks.
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