OK, you have to install a single door electromechanical access control system. You have decided upon the lock hardware and the credential reader/controller or standalone. Most of these products require direct current (DC). Electric strikes depending upon the solenoid will operate on either AC or DC or both. Electric strikes that are operated on AC buzz when power is applied, notifying the user when the door can be opened. However, this buzzing eliminates the possibility of operating an AC electric strike as Fail Safe.
You need a power supply to complete the package. The wire run has been determined in order to calculate the total amperage requirements. What is the output current required? What size and type of power supply do you need? Aren’t all power supply pretty much the same and only vary by the amperage? The short answer is no. There are different types of power supplies better suited for specific applications.
This article will provide answers for a better understanding of power supplies and their differences in relationship to lock hardware and locksmiths. We will start with the basic: “What is a power supply?” For the purpose of this article, we will base our discussion on direct current power supplies mounted into enclosures that provide filtered and regulated power.
A power supply takes the basic input power and converts the voltage and current characteristics to provide continuous power output at a specific amount in order to accommodate the operation of the electromechanical equipment. Most electromechanical locks, readers and keypads and 99 percent of all electric latch retraction operate on 24 Volts Direct Current (VDC), the voltage of choice for most companies supplying access control hardware. Some products operate on 12VDC or 12 to 24 VAC/VDC. Alarm companies more commonly use 12VDC, as their products require little current.
Note: There is an advantage to using 24 volt access control hardware. It requires roughly half the amperage of operating using 12 volt hardware. Low amperage cooler, more efficient operation.
Power supplies provide specific voltages at different amperages. For example, filtered and regulated power supplies are available with usually a minimum of one Amp to five Amps or more.
When designing an access control system, there are a number of considerations regarding the power supply. Most power supplies have a fixed output. Some power supplies have a potentiometer to adjust the output voltage to about 10 percent over rated. Some power supplies with battery backup have two channels, one that output the specified current and a second that has outputs upwards of 10 percent above the specified in order to charge the batteries.
An improper power supply can result in a malfunctioning or inconsistent functioning system, as there is not sufficient amperage provided to properly operate the locking mechanism(s). Even worse is the early demise of sensitive electronic components resulting from too much voltage. This can result from a power supply whose output voltage is not within the tolerances of the components, or by a single output power supply where battery backup is required and the components are sensitive to voltages above twenty-four.
This can also result when a power supply does not provide “filtered and regulated” current, which many components require for optimum operation. An unregulated power supply will output its rated voltage and current only when under load. With no load (power off), the unregulated power supply’s output will be greater (when power is turned on), resulting in possible damage to sensitive electronic components.
Sensitive active components are electronic devices that require a certain minimum voltage or current to perform a function, such as controlling the flow or direction of current. These devices include relays and are very sensitive and susceptible to damage from overpowering during start up, static discharge or kickback voltage that can occur when powering down.
Command Access Technologies electrifies most commercial manufacturer’s locksets and exit devices for remote control by an access control system or a momentary contact. The company has developed...
If an access control system involves more than a single door, a single power supply won't suffice.