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