Power Supply Overview

July 6, 2010
Choosing the right power supply is crucial for your electronic access control or CCTV installation.

Specifying the right power source for a project is as important as any other element of the design. Specialized power supply products are available for access control and video systems.

With the growing popularity of UTP and IP video, additional products are available. Today’s locksmiths need to know what’s on the market so they can win those projects.

Power supplies may require the services of an electrician to provide the connection of line voltage. In most jurisdictions, working with line voltage wiring requires licensing and insurance.

The typical work-around for this is to use a plug-in type wall wart, or to order the power supply with a line cord. However, your choice of a power supply should be guided by other criteria other than the issue of how you will connect it to line voltage.


Securitron is a major supplier of access control power supplies, so we asked their technical support staff for some pointers on how to select a power supply. Following are the Ledger’s questions and Securitron’s answers.

Under what circumstances are wall wart type transformers/ power supplies used?

Typically plug-in type transformers/power supplies are used in installations that do not require battery backup or a fire alarm interface to the locking device, such as a failsafe electric strike or magnetic lock on a interior non fire rated/exit door.

What are the advantages of linear power supplies and when should they be used?

Linear power supplies deliver the cleanest DC voltage available. Typically card reader systems, PIR motion sensors and a variety of electronics that utilize internal processors recommend linear power supplies to eliminate spikes and/or electronic noise that can interfere with its electronics. Excessive spikes/noise can also shorten the life of the electronics.

What are the advantages of switching power supplies and when should they be used?

Switching power supplies are best used with simple electronic devices not susceptible to electronic noise or spikes in the power input. Some processor-based products utilize front end protection so that a switching power supply can be used, but this should always be verified before installation.

What exactly is UL Class 2?

Class 2 defines the portion of the wiring system between the load side of a Class 2 Power Supply (beginning from the outside of a cabinet or machine) and the connected equipment. Due to its power, current and voltage limitations, a Class 2 circuit considers safety from a fire initiation standpoint and provides acceptable protection against electric shock.

Such Class 2 circuits have reduced requirements regarding insulation, wire size, de-rating factors, over-current protection, wiring methods and installation materials. Considering Class 2 in a system can be an important factor for reducing the cost and improving the flexibility of the system.

What are the advantages and disadvantages of providing backup batteries with the power supply?

Back-up batteries are needed to keep failsafe locks in the locked condition during power failure to the building. This is critical on perimeter doors and secured areas. It is also desired on failsecure locking systems to gain access during power failure via the access control device (card reader, keypad, etc.)

What is your most popular power supply, and why do you think it is popular?

Our most popular power supply is our BPS-24-1. It is a 24 Volt DC 1 amp power supply with battery charging and fire alarm release as standard. It is desired for its clean linear DC voltage and standard options. I think it sells well because most systems out there are 24VDC and are relatively small (four or less doors) which works out perfect for the BPS-24-1.

What online resources for power supply selection and system design are available from Securitron?

There are several on-line resources such as power supply selection charts and other product selection charts. Currently Securitron is developing the Door Control Wizard version 3 that will configure a single or multiple door configurations along with a magnetic lock bracket selector, gate product selection wizard and mobile door control wizard for smart phones.

For more information on Securitron products, contact your local locksmith distributor or visit www.securitron.com


Setting up systems incorporating electrified exit devices such as the Von Duprin EL requires specialized power supplies to satisfy the high current inrush required by these locks. Unless you provide the right power supply, you are in for problems because the Von Duprin EL simply will not operate properly if not fed properly. Electrically speaking, a Von Duprin EL is comprised of two parts: the solenoid which mechanically connects to the latch (or rods), and an electronic module that automatically controls the power to the solenoid to limit current draw once the initial application of power to the device has retracted the hardware an unlocked the device.

Von Duprin EL devices are frequently used for pairs of doors, banks of doors, and inner and outer vestibule locking systems. It is not uncommon for card readers, motion sensors, timers and handicapped door operators to also be incorporated into the same openings.

The ALTRONIX StrikeIt combines power, control timers, auxiliary relay outputs, auxiliary power, and fire alarm interface into a single box solution for these openings. Using an integrated solution such as the StrikeIt ensures that your system conforms to Code, and will not require on site ‘engineering’ that will result in a rat’s nest of relays and wires which no one will document, and will be almost impossible to troubleshoot after six months.

StrikeIt is UL listed and MEA/CSFM approved.

The StrikeIt has dual channels and is designed to provide 24VDC power for a maximum of two electrified panic devices with very high inrush requirements.

Each channel has an adjustable relock delay input which can be configured to control either a pair of doors simultaneously or provide independent control of two single doors.

Each channel also has a pair of relays which can be configured to trigger or otherwise control external equipment such as automatic door openers or electromagnetic strikes. External trigger devices such as ADA push plate switches, motion sensors or timers may be used with StrikeIt

StrikeIt can control automatic door operators where the doors are always locked or where the doors are unlocked during the business day. When the doors are locked, the StrikeIt delay allows time for the EL to activate before signaling the door operator.

While the doors are unlocked for the day, “Follower 1” & “Follower 2” may be used to enable handicapped push plates.

Two un-switched auxiliary voltage outputs are provided for powering keypads, electronic timers, or relays.

StrikeIt offers a programmable FACP interface will either provide power or remove power to the lock outputs when activated.

The device’s operation may be observed using LED diagnostic/status indicators which monitor input AC voltage, FACP status and to distinguish between an open and a short on the lock output terminals.

Intelligent logic provides protection against accidental shorting of lock outputs.

Features include:

Two 24VDC individually or simultaneously controlled lock outputs rated @ 16 amp for 300ms.

One 12VDC filtered regulated auxiliary output rated @ 1 amp continuous supply current. (Not affected by FACP trigger)

One 24VDC filtered regulated auxiliary output rated @ 1 amp continuous supply current.(Not affected by FACP trigger)

Two delayed follower form “C” relay outputs rated @ 1 amp/28VDC. Delay time is selectable .5 seconds or 1 second.

Two (2) follower form “C” relay outputs rated @ 1 amp/28VDC. Relays energize while input is closed.

Input 115VAC 50/60Hz, 1.9 amp.

Two (2) N/O Trigger Inputs.

Built-in charger for sealed lead acid or gel type batteries.

Automatic switch over to stand-by battery when AC fails.

Maximum charge current .3 amp.

Green LED indicates input 115VAC present.

Green LED indicates panic device status (short, open or triggered).

Red LED indicates when FACP disconnect is triggered.

Fire Alarm Disconnect:

– Normally Closed FACP trigger input.

– Programmable Fire Alarm Disconnect options:

a) Removes power to outputs and disables delayed follower relays.

b) Connects power to lock outputs and enables delayed follower relays.

Enclosure accommodates up to two (2) 12VDC/7AH batteries.

Dimensions: 13.5”H x 13”W x 3.25”D.

For information on Altronix products, contact your local locksmith distributor or visit www.altronix.com..


Power over Ethernet (PoE), and Power over Lan (PoL) are technology that allows both data and power to be provided over an Ethernet cable to an endpoint device such as an IP video camera, card reader, telephone or wireless access point.

By putting the power for the endpoint device over the Ethernet cable, it eliminates the expense associated with providing separate cabling and equipment to an endpoint.

By adding Power Sourcing Equipment (PSE) called Endspan Equipment into the Ethernet switch, or by adding Midspan Power Insertion Equipment after the Ethernet switch will combine the data and power at the source to be sent through the Ethernet cable. The power from the Ethernet cable can then be tapped at the endpoint with a Powered Device (PD) to operate the access point.

Under normal operation the PSE supplies a nominal DC. Voltage of 48V at 15.4 W

Altronix NetWay8/NetWay16 are Midspans designed for use with PoE and non-PoE compliant IP video surveillance cameras with non-PoE switches to provide power and pass data (video) for PoE compliant cameras/devices.

They are available with eight or 16 ports in a space-saving 1U EIA 19” rack mount chassis. Cameras/devices may be located up to 100m (328 ft.) from the NetWay unit.

A NetWayXT repeater module can be utilized to extend the distance an additional 100m (328 ft.) for a total range of up to 200m (656 ft.). A maximum range of 600m (1968 ft.) is possible using multiple repeaters, based on camera/device port requirement.

Since many existing IP cameras are not PoE, NetWay Midspans are capable of supporting non-PoE compliant fixed and PTZ IP cameras by utilizing NetWay1512 or NetWay3012 adapters. These are modules which have the required Category RJ-45 jacks as well as voltage output terminals.

The Netway provides diagnostics using LEDs to assist the installer analyze cabling and identify endpoint status.

To read additional Locksmith Ledger articles on power supplies, visit tinyurl.com/power0710.