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Uninterruptible Power Supplies
Uninterruptible Power Supplies for Security Systems

We have seen during recent natural disasters, just how opportunistic some thieves can be when the power goes out. While many alarm panels feature a backup battery (at least as an option), surveillance systems rarely do - most likely due to their increased power requirements when compared to relatively low-power security alarm systems. Fortunately, at its most basic level, a UPS is very easy to install, and selection only requires some fundamental mathematics. While the mathematics is rather simple, we do deal with some electrical principles which may be unfamiliar to you.

How does a UPS work?

A UPS is essentially made of four components
- A battery: this is what provides power while mains power is unavailable.
- A mains inverter: this converts battery power into mains power.
- A battery charger: to keep the battery totally charged whenever mains power is available.
- A power relay: this is what “detects” that mains power has been lost, and within nano seconds switches to the backup battery source and mains inverter for power, providing a seamless power supply (hence the name, uninterruptible power supply). The fraction of a second that it takes to kick in is easily compensated for by almost all modern electrical equipment.

Some UPS systems will go one step further, and run from the power inverter constantly, so there’s not even a fraction of a second delay. It also helps smooth out any power fluctuations that naturally come from the power grid, further protecting sensitive equipment. Intelligent circuitry can also communicate with computers and other equipment, to safely shut them down, rather than a hard power-off when the battery is depleted.

What surveillance equipment needs to run on the UPS?

You only need to power critical parts of the system with the UPS to gain the benefit during a power outage, but it is important to make sure you have all critical components connected. If you’re using IP (network based) and forget to power the network switch, the rest may as well be switched off anyway because the camera signals won’t make it to the recorder. However the surveillance monitor you use to perhaps watch the feed during store opening hours, can easily power off without affecting any recordings.

If your entire surveillance system is powered from a central point (eg, your cameras all have video and power leads running back to the recording system), retrofitting a UPS is quite straight forward. If your cameras are powered at their remote locations, it could be a little more challenging.

How do i determine what size UPS i need?

The old saying “bigger is better” is relatively accurate. However, with a bigger unit comes greater expense. So it’s prudent to size the UPS according to your needs.

There are two main specifications in a UPS which you’ll need to consider.
- The first is the capacity of the inverter unit, which is usually expressed in VA (Volt Amps). This VA rating illustrates how much power the UPS can deliver at a given moment.
- The second is the battery capacity, which is usually provided as a voltage (eg 12V) and an ampere hour rating (such as 7.2Ah) - eg 12V / 7.2Ah.

NOTE: Watts and Volt Amps are not the same thing. For simplicity, it’s best to simply calculate the VA (Volt Amps) for each appliance, and compare that to the VA rating of the UPS. If you’re only connecting one or two devices and Watts are specified for each appliance, watts can be compared instead.

Thanks to rigorous mains-power compliance required in Australia and New Zealand, all mains powered devices will show the approximate power they will consume. To get the VA requirement, simply multiply the voltage with the current (expressed in Amps, or A for short).

NOTE: If you have a camera power supply or similar which says “mA”, this is milliamps, or x0.001A. If it says for example, 1,000mA, this is simply 1A. So a 12V / 1000mA power supply is simply 12VA.

Once you have added all the “VA” together, you know the total power requirement for your system. This must be below the rated VA of the UPS, or it will not power the system - you will simply overload the power inverter in the UPS.

Once you have determined your surveillance system can be powered from the inverter inside the UPS, you must determine how long it will run it for. This is determined by looking at the battery specifications. This is expressed as voltage / ampere hours. This means the battery is rated to deliver that voltage and amps (VA) for 1 hour. This gives us a very simple number to work with. For example, a common battery is 12V/7.2Ah. This means it will deliver 12 volts, at up to 7.2 amps, for 1hr. Or 12 volts, at up to 1 amp, for 7.2 hours. The numbers can be shuffled around but must equal the same total (and of course, the voltage doesn’t really change).

Using these numbers in a practical example

In our example we’re going to use our 4-channel surveillance system. This provides a four-channel recorder, as well as four cameras, which are all powered by the DVR too. This unit requires 12V 5A power supply (giving us 60VA) to run our entire system.

If we use our 1500VA UPS, it provides us with approximately 192VAh (the provided specifications state that the unit houses 2 x 12V/8Ah batteries). That means if our load is 1VA, it will run for 192 hours, 10VA for 19.2 hours, and so on.

To determine how long our system can run from using this UPS, it’s simple division. Total VAh (192) divided by the total VA (60) of our system. We get 3.2. That means effectively that this UPS will run our DVR and its four cameras for up to 3.2 hours, before the batteries run flat. You can use this duration to determine if a UPS will cater for your needs.

Now there is some efficiency within electronics, age of batteries, ambient temperature, and other factors to consider which all affect battery performance and power requirements. But using these whole numbers provides a good guide that is near-enough. The reality is that the rated power is usually a “maximum”, and the system will average less power consumption. But it’s better to plan for worst performance, than have it run flat when you think it will go the distance.

What if it’s not long enough?

The reality is that most UPS systems will only cater for “standard” power outages scenarios, from a few minutes to a few hours due to line works, a tree branch, or other relatively brief interruption. For a natural disaster scenario where power supply may be interrupted for days or weeks, a generator is usually the only option to keep power flowing.

How do i install one?

Using the simplest explanation possible, you connect the UPS to mains power, and any devices you want “protected” into the UPS. With a surveillance system where you have equipment installed, possibly tens or hundreds of metres of cabling between the recorder and the cameras, things can be a little more complex depending on the installation. If you have discovered that each camera is powered near its installation point, and not at a central location, it may be worth considering running new power cables to each camera from a centralised location. It is possible to place a small UPS on each camera, but this will often be more costly. If running new cables is difficult however, this may still prove to be a cost effective solution once everything is considered.

There is rarely any programming of the UPS required, it’s very much plug and play. If you’re using smart shut-down features in your UPS, use the instructions included with your UPS to activate this functionality. But for most surveillance systems this won’t be the case.

For assistance choosing a UPS, a surveillance system, or matching one to the other, drop into your local Jaycar store. Our team are all very knowledgeable and can help make sure your requirements are covered in the most cost-effective way.