Recent advancements have the limelight shining on power supplies, particularly where access control is concerned.
By David Corbin
Power supplies typically suffer one of two fates during the life of a project. Often they are the first thing to be value-engineered out of an access control system. Alternatively, an installer might just install the same power supply on every job simply because it works.
While power supplies have previously taken a backseat to sexier system components such as integrated maglocks and multi-attribute credentials, several recently released power supply products have stepped into the spotlight by reducing system costs for building owners, while increasing integrator and installer profitability. Such newer power products provide access control efficiency, reliability and remote system diagnostics.
Achieving Higher Efficiencies
It’s impossible to talk about the efficiency of an access control system as only measured by the efficiency of a power supply. There has been a trend toward lower power locking devices in the marketplace. Solenoid-based devices have steadily been decreasing in power draw and now you can find solenoids that draw 1A of inrush power or less. Additionally, some manufacturers have moved away from solenoids entirely using motors and other electronic actuators that draw less than a half-amp of inrush and holding currents approaching 15mA or less. This is leading to a shift in power supply design and application.
Previously in a failsafe application, the majority of the power consumption of the door was associated with the locking device. With the new lower power locks, 90% or more of the door’s power consumption can be attributed directly to the power supply. This is due to a number of factors including the latent power consumption of relays on the power supply as well as the tendency to oversize power supplies for the application. The latter is more evident when an installer uses the same power supply on every job. As a result, at least one power supply manufacturer has moved to provide power supplies more closely tied to the actual consumption of the locking devices. Closely pairing a low-powered lock with a comparably sized power supply can reduce power consumption of the door by 90% or more compared to solenoids on an oversized power supply.
Previously in a failsafe application, the majority of the power consumption of the door was associated with the locking device. With the new lower power locks, 90% or more of the door’s power consumption can be attributed directly to the power supply. This is due to a number of factors including the latent power consumption of relays on the power supply as well as the tendency to oversize power supplies for the application. The latter is more evident when an installer uses the same power supply on every job. As a result, at least one power supply manufacturer has moved to provide power supplies more closely tied to the actual consumption of the locking devices. Closely pairing a low-powered lock with a comparably sized power supply can reduce power consumption of the door by 90% or more compared to solenoids on an oversized power supply.
The adaptation of low-powered locks has also opened up the market to integrated Power over Ethernet (PoE) door locks. Integrated PoE locks are a world apart from what are being marketed currently as PoE-compatible or PoE-friendly products. Simply put, an integrated PoE product will accept a Category-5 cable directly into the lock body, and run off of the 50V typical of PoE or PoE+ injector. PoE-compatible products are merely locking devices that are compatible for use with a door controller that accepts a PoE input. This distinction is important.
Integrated PoE products actually physically decrease the number of components in the access control system by integrating the door controller directly into the locking device. This accomplishes two things.
First, the overall power consumption of the system is reduced, because you have fewer components drawing and consuming power. Second, it reduces the number of possible failure points in the access control system. As an installer or the person troubleshooting a system with a failure, each splice point is a potential point of failure within the system that can contribute to the overall failure of a door to perform as expected. With integrated PoE locks, splices and components are kept to a minimum. Additionally troubleshooting is made easier by the plug-and-play nature of the integrated product. Simply plug in to the Cat-5 and see whether or not data is being transferred.
The trend toward efficiency impacts the overall cost to the building owner outside of the obvious decrease in energy consumption. When a lower efficiency power supply is used, it results in additional waste heat generated by the electronic components of the power supply. As a result, the components on the circuit board are subject to higher operating and ambient temperatures. This decreases the expected life of the product, resulting in more frequent product replacements, access control system downtime and additional labor costs across the lifespan of the building.
Capacitors, for example, have a nearly exponential decrease in useful life for a given increase in ambient and operating temperature. The fact that there are now power supplies on the market that can essentially shut off the transformer and remove load from the electrical component while continuing to power the access control system for several hours shows that these effects can be decreased significantly, to the benefit of building owners.
Power Supplies Getting Smarter
Another capability being built into an increasing number of power supplies is for remote data monitoring and diagnostics, a typical feature in rack-mounted PoE midspan injectors. Products with this feature are typically known as managed midspan injectors. A few manufacturers are offering this capability built into the traditional power supply form factor. These power supplies are connected to a local area network (LAN), either with or without Internet access. Attaching the power supplies to an Internet-connected LAN allows for enhanced monitoring and management capabilities.
Managed power supplies have various capabilities depending on manufacturer (see sidebar), but common features include monitoring of voltage, current and on/off status of each monitored output. This interface can be accessed from any Web-connected device if the power supply is attached to a network with Internet access. Because of this it is important to make sure that the default manufacturers’ login and passwords are changed during the installation and startup of a system connected to the Internet.
Additionally, some models allow you to set alarm conditions if the voltage or current fluctuates outside your preset high and/ or low parameters. In the event of an alarm, you can typically arrange for the power supply to automatically E-mail the building maintenance manager. This may seem fairly insignificant; however, if there is an intermittent short in the power transfer to an electrified lockset, you might only have a short when the door is slammed shut. If left alone, eventually the short could cause damage to the lockset. With remote monitoring capabilities installed the intermittent short can be taken care of before any permanent damage occurs to the system.
Another example of the benefit of remote monitoring is in monitoring the status of your battery backup. Imagine an access control system that gets installed with 12 hours of battery back-up. In five years’ time trickle charging the batteries, how much capacity do you truly have? If the office closes at 5 p.m., and the power goes out at 7 p.m., security will be maintained as long as the battery holds out, leaving the building potentially either unlocked or inaccessible and unmonitored until morning. With remote system diagnostics tied to the power supply, the right per-son is alerted when the power goes out, and then can be alerted again when the battery voltage decreases further (low battery warning) so action can be taken to prevent full loss of power.
With remote monitoring capabilities, building owners and facility managers are able to make a variety of informed decisions to ultimately save time and money, and establish peace of mind.
Taking Stock of the Lock
As previously mentioned, there has been a significant increase in the number of customers switching from solenoid-based locking devices to low-power locking devices, which is altering the function of the traditional power supply. As the industry drives to these more efficient locking solutions, the power sup-ply increasingly becomes the leading cause of energy consumption, and people are starting to pay attention.
In a traditional access control system, the power draw of the solenoid locks (6-12W per door) overshadows the latent power draw on the transformer on the power supply (5-6W for a linear supply and 2-3W on a switching power supply dependent on power capacity). Now, there are locks on the market drawing as little as 0.2W per door and lower. If you are still installing the same power supplies on these systems, you may be causing the building to consume more power than necessary.
Recently introduced power supplies have cut the latent power draw of the transformer down to the 10mW range by going dormant for significant periods via energy stored in batteries. These power supplies are taking efficiency to a new level. A 90% efficient power supply that has to be on 24 hours a day is ultimately less efficient than a power supply that will go dormant for significant periods of time each day.
Low energy consumption locks have done a fantastic job reducing lock power. Overall system consumption, however, is still quite high, but a super-efficient power supply can lower overall power consumption by more than half. As manufacturers continue to develop locks that require less power to operate, it only makes sense that they will provide integrated products with the similar goal of lower power consumption.
Customers already using lower power locks are now looking for next-generation power supplies. Customer demand is truly the best challenge, pushing the market to innovate new products and a more sustainable solution.
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