Powering Up Access Control Systems

If an access control system involves more than a single door, a single power supply won't suffice.


Power supplies are an important part of any electrical access or security system. The power requirements for an access control system are therefore typically divided into two categories: power for the controls/readers and power for the locks. In reality, the power is used for several purposes...


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Power supplies are an important part of any electrical access or security system. The power requirements for an access control system are therefore typically divided into two categories: power for the controls/readers and power for the locks.

In reality, the power is used for several purposes, depending on the system. Power will be required for:

Readers: Card readers usually require clean power at precise voltage and current. Some readers provide some from of internal regulation, as an attempt to prevent fluctuations which disrupt the reader’s proper operation.

Controllers: Hard-wired access control systems (as opposed to standalone battery powered ones) generally require an external power supply for power. Some system manufacturers provide integral power supplies.

Communications: Access systems which involve multiple doors and proprietary dedicated networks frequently require that power provided to ‘hold up’ the network. Although this power is extremely low current, it must be highly regulated and filtered against noise and interference.

Locks: All electric locking hardware requires power. In the case of electromagnetic locks and other failsafe type equipment, the power must be available in order for the locking device to be ‘locked’. Fail-secure locking devices require that power be applied to ‘unlock’. Electrically actuated trim such as outside levers used with exit bars and mortise locks use power to switch a solenoid in the trim, thereby enabling the lever so that the lever will actuate the associated locking mechanism.

Frequently you will be able to use a single power supply for a system, but if your system involves more than a single door, or uses a specialized locking device or reader, a single power supply won’t suffice.

For example, some readers require a higher capacity power supply in order to achieve extended read ranges.

Another situation would be if you have to run wiring over distance to reach a door location, the power required by your system components and the voltage drop occurring in your wiring will become a critical issue.

Many specialized locking devices require high inrush currents, or will produce what can be generally called ‘electrical noise’, which can be harmful to other components in the system, and otherwise affect the proper operations.

So as often as not, multiple power supplies and separate wiring will be used for the system.

Experienced system designers will anticipate such issues and provide adequate power supply resources initially rather than try to retrofit them to solve system performance anomalities which will occur once everything is hooked up.

Since many door control systems will involve life safety issues (that is they are required to provide safe egress for occupants and emergency entry for responders), power supplies may be obtained with features which allow them to be connected to emergency and fire systems.

The term “Secondary Power Supplies” refers to additional power supplies incorporated into a system. They may be used to augment the primary supply when power requirements exceed the capacities of the primary. They may be situated remotely from the primary power supply in order to avoid voltage drop and effectively “distribute” power. They may also be incorporated to provide redundancy to a system, so that if a primary power supply fails, there is backup. Secondary power supplies are also used to upgrade older installations where revised or new codes mandate additional annunciation.

This month’s product gallery offers a small sampling of power supply products available for access control systems.

Altronix StrikeIt™

StrikeIt™ Panic Device Power/Controller Series is one of the new series of branded integrated products from Altronix. It is designed specifically to handle the high power demand required to activate panic device egress hardware.

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