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Selecting the right power supply for the job

Power supplies are a basic component of surveillance and security systems - but they are often taken for granted. It goes without saying that each product has specific power requirements and operating range, and there are numerous variables to consider when determining how to provide power, given the various solutions which have evolved for today's advanced integrated security systems.

The sheer number of power supply products available can be a challenge to evaluate relative to the actual power requirements of the numerous devices that comprise a system. Understanding more about power supplies and how they are incorporated into various systems and configurations can provide strategic value when designing and implementing professional security systems.

This article will shed light on the expansive range of power system products. It will outline the selection of a power supply that meets specific product needs; the importance of quality and reliability on product and system performance; the benefits of centralized power systems; and how power systems can improve efficiency and lower overall costs.

Selecting a Power Supply Solution

The "How Stuff Works" Website ( compares the flow of electricity to the flow of water through plumbing pipes. The three basic units of electricity are voltage (measured in volts), current (measured in amps) and resistance (measured in ohms). When comparing electrical current to water flowing through plumbing, it is helpful to think of the voltage as the water pressure, the current as equivalent to the flow rate and the resistance as similar to the pipe size. Increasing the voltage will make more current flow in the same way that higher water pressure will push more water through a garden hose. Electrical power is measured in watts, which is the voltage multiplied by the current - increasing either will boost the resulting power. Beyond the basic physics dealing with electricity, there are several critical issues to address when selecting a power supply for professional security applications:
- What type of cabling is being proposed for the project? Does it conform to the system's needs?
- What is the distance between the power source and the device it is powering?
- What are the voltage and current requirements of the device and the estimated voltage drop due to wire size and distance?
- Does the device require isolated power?
- Will the power supply be subjected to harsh environmental conditions?
- How much additional power above and beyond the device's requirements should be added as a safeguard? (Altronix typically recommends a power supply can provide 20 percent more power than the system requires).
- What agency approvals are required and which codes need to met?

The fact is that every security system is different, and every system requires a power supply product - or combination of products - specific to its needs. As a result, there is an extensive selection of power supply products available. To illustrate the number of products involved, consider that the Altronix Product Guide includes more than 150 pages of solutions. The breadth of choices ensures that a system designer/integrator can match the power supply that best satisfies the requirements of each product in their system.

Reliability Is Critical

Serving a mission-critical function in today's companies and institutions, security and surveillance systems cannot afford to stop operating in the event of a power outage. One of the basic requirements of power systems is to provide reliability and continuous security system operation. If a camera never blinks, it is in part because there is a power system that keeps it from doing so. An uninterruptible power source (UPS) is integral to continuous system operation. A UPS includes a battery backup to provide uninterrupted 24VAC for cameras during normal, brownout and power fail conditions. Other components of reliability include short circuit and overload protection and fused or resettable PTC-protected outputs (a positive temperature coefficient [PTC] element is a power supply circuit breaker).

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