Thursday, January 26, 2012

When Lightning Strikes Alarm Systems

April showers bring May flowers, or so goes the old cliché. Warmer weather also brings with it thunderstorms and power surges galore. All too often the result is false alarms, lost data and the destruction of high-tech electronic equipment.
Although lightning is a major concern during good weather, it doesn't have to be warm out for electric motors, smelting operations, heavy industry and other electrical concerns to spell big trouble for the equipment for which fire and burglar alarm technicians are responsible.
Lightning is a common concern for alarm technicians because of the suddenness with which it can strike. The damage that it can cause may involve a lone device connected to an internal low-voltage cable, like an addressable manual fire pull or an individual circuit board. Or it might involve an entire motherboard within a fire or burglar alarm panel.
Sometimes the damage is light while other times it can be catastrophic, tearing through the system from one end to the other. Having a fair understanding of how lightning works and by using good installation practices, along with quality equipment, technicians can limit the amount of damage that does occur.

Mechanics of a Lightning Strike
Any device that connects to a metallic wire can suffer damage at the hand of lightning. This is true whether the strike is direct to the cable itself or indirect by virtue of inductance. Sometimes no matter what you do, lightning will do irreparable harm.
Concerning a direct hit to equipment, lightning can enter through multiple paths from outside the structure. A good example is a campus environment where there are many buildings.
Lightning also can enter the structure through the public electric bus via outside power lines or one of the many paid subscription services now available. Examples include conventional telephone, cable television networks and satellite dish systems.
In a burglar or fire alarm system, once lightning enters the equipment through one of the methods cited above it can migrate to a signaling line circuit (SLC), initiating device circuit (IDC), notification appliance circuit (NAC) or some other low-voltage line. Another example is the coaxial cable or twisted pair unshielded wire that carries video images in a CCTV system.
"The focus is usually on SLC loops [burglar and fire alarms], low-voltage data [networks] and coax cable [CCTV].
Manufacturers are well aware of the problem lightning poses and for this reason they commonly build a limited amount of surge protection into their electronic systems at the point of manufacture. In most cases this is done right on the motherboard itself.
This ploy most often includes add-on printed circuit (PC) boards and any number of subsystems, such as smoke detectors, glass breakage sensors and others. And yet damage or total destruction can and often does occur when lightning appears on the scene.
One fire alarm manufacturer uses optical isolation on the data loops to minimize lightning damage. Damage in this case often occurs when lightning induces a high voltage current in the internal wiring of a building. This can be especially problematic in campus environments where data lines travel under ground between buildings.
This design incorporates the idea of isolating the grounding differential from the other buildings. Nice little spark gaps and it does help, but the problem is, when incorporating second-rate surge suppression, you get a feedback loop up the case ground into the smart chip.
When you consider the multiple pathways over which lightning can travel, you must also think about distance with regard to proximity as it pertains to the surge protection device that acts to clamp the surge voltage and route the strike current to earth ground.
This is true whether it involves external surge protection or those internal to the device itself. Many years ago an engineer told this writer that lightning will often travel well beyond the point where the surge voltage is clamped. All too often this ends up damaging critical circuits, not to mention the possibility of arcing within the panel itself.
The most panels can handle some of this current, but not all of it. This is especially true where there's a significant voltage differential between equipment grounds of all the interconnected equipment.

Think Ahead When Installing
As mentioned earlier, one common application where lightning can cause considerable damage involves integrated systems across multiple buildings. Because of the matrix of wires that travel to and from each building, being installed either overhead or underground, the propensity for damage is considerable.
In this case a single head-end system may be employed to provide a number of low-voltage services, such as fire, security and/or CCTV protection. Here, especially proper precautions must be taken, such as the use of quality surge protection.
One case in point is a motel with multiple buildings serviced in the summer of 2008, by Nick Markowitz, owner of Markowitz Electric Protection of Verona, Pa. According to Markowitz, the location experienced a lightning strike that damaged a fire alarm system, three cameras and a washing machine. The lightning affected systems in three separate buildings by first entering a restaurant and then traveling throughout the entire campus.
"The camera system is one of those cheap cameras-in-a-box deals that uses four-wire telephone cable. One of the cameras is located in the restaurant and is fine, but another one took a hit and the wiring was damaged," says Markowitz. "The other two cameras were converted from phone wire to inline powered coax and lightning took out the converters and power injectors."
Lightning entered through one of the cables that crossed between the buildings, Markowitz reports. A close examination revealed that there wasn't any surge protection on any of the low-voltage cables that serves video or any other centralized system. And yet damage was spotty, which Markowitz found puzzling considering the severity of the hit.
"I find it strange that the monitor and one of the other cameras were fine but all the rest was trashed. Usually when lighting strikes like this, everything goes at once," he adds.

Equipment Circuit Design Changes
Manufacturers have changed the way they construct and package components contained in their low-voltage systems. Included is the way those components are installed on PC boards. Both of these factors have altered the way alarm technicians protect their electronic systems from lightning, says Pecore.
"In 1997, Stormin Protection Products officially became an engineered lead business because the projected sales in the area of low-voltage surge suppression for fire alarm, CCTV and access control systems will be in greater demand as the progress of SMT [surface-mount technology] literally took over the industry," says Pecore.
SMT technology allows manufacturers to reduce power consumption as well as extend the length of time batteries will provide backup power. If nothing else SMT components have allowed manufacturers to reduce battery size to meet a specific code requirement, such as standby time. SMT technology poses a problem because it represents a relatively low impedance to lightning.

“SMT technology for an old guy is a dirty word. It spells out one thing, nothing but trouble,” says Pecore. “Manufacturers took all the linear and high capacitance devices off the board and left me with a featherweight that if I hiccup just right, it will blow.”
Design engineers have eliminated linear power supplies, replacing them with Wheatstone bridges. Also, low-impedance capacitors and resistors have replaced heavy-duty capacitors and resistors, and smart chips have replaced entire printed circuit boards. 

“Low Pico Farad devices have also replaced other components — all for the sake of reducing current draw,” says Pecore. “As a result of these changes, fire alarm panels (and other electronic systems) have become more susceptible to surges, impulses and ground strikes.”
The idea is to raise the impedance of the panel, not lower it, and to do this the installer has to look for ways to create an alternate path that looks more inviting to high-voltage lightning than the panel’s motherboard.

According to Pecore, the answer is an inline series hybrid three-stage, two-tank circuit that works to impede strike current while shunting it to ground. This is accomplished by focusing on the characteristic frequency associated with lightning.
Thanks to SSI Magazine FOR HELP & Thanks to John Pecore, President at Stormin Protection Products Inc

Outdoor Wireless/ Wire Security Cameras – All You Need to Know

A little research can go a long way in ensuring that the right equipment is purchased at affordable prices. Most security equipments have a number of options available in the market and improper understanding can either lead to a bad purchase or an unnecessary purchase. Let us understand the basics of outdoor wireless security cameras that will help you in buying the right outdoor camera for your security system.

Different Outdoor Wire / Wireless Security Cameras

Analog and Digital Cameras

These are the time-tested devices that have been used since a long time in different security systems. They can be connected to the video surveillance systems through wires. These cameras are less expensive as compared to their digital counterparts but they are difficult to install.


You can use wired devices that can be powered by connecting their wires to the central power unit. A better option is the wireless camera that does not need wiring but needs to be connected to power outlets. In case you are installing cameras where power outlets are not available and cannot be made available, then consider using wireless cameras that run on batteries. These cameras can be easily installed at any place but need to be constantly monitored for battery changes.

Lux Number

Outdoor Cameras are exposed to different lighting conditions throughout the day and these conditions also vary in different weathers. Use cameras with low Lux number which signifies that the cameras can cope with dim lighting conditions. You should also invest in night vision cameras that use infrared technology to capture images even in pitch dark conditions.

Weather Proofing

Cameras are sensitive electronic equipments and hence, they need to be protected from the vagaries of nature. While investing in an expensive camera make sure that you also buy a weather proof casing to guard your camera from excessive heat and moisture. In very cold regions, cameras with insulated casings should be purchased. For hot weather conditions, casing with exhausts will come handy.

Protection from Vandalism

It is important to protect your equipment from vandalism. Buy an outdoor camera with sturdy material. Use a casing that can protect any on-the-spur attack on the camera. You can also buy dome-shaped cameras and casing that gel well with the surroundings and make these camera less visible, thereby, protecting them from any danger.

Ideal Transmissions

Using wireless devices has a drawback that there signal transmission can be weak. Make sure that you buy equipments that can transmit data over the distance that you require. Factors such as big trees, metals in the walls and bad weather can hinder wireless transmissions. Hence, it always better to invest in good devices with wide transmission range. You can also invest in good quality signal receivers that can capture low quality inputs as well.

Picture and Sound – While selecting a camera, pay special attention to its picture quality. A low screen resolution will not be able to give quality inputs. Audio wireless outdoor security cameras can also be purchased with audio compatible devices.

Wednesday, January 18, 2012

Voltage & Amper Guide for your CCTV Camera

Voltage drop is a term that we hear about all the time in the surveillance industry. While many people talk about it and use the charts and calculators provided by different sources, I think a smaller amount of people fully understand the physics behind it. Today I want to give a quick review of the ideas behind voltage drop and then some practical tips for installing security cameras or any other equipment.
Here is the equation for Voltage Drop:
Voltage drop=( 2 * (length of run in ft.) * (resistance factor) *(current load in Amps))/1000

The length of the run is pretty simple; it is how long the cable is between the camera and the power supply.
The resistance factor is determined by the wire used and there is a chart in the NEC Chapter 9, Table 8 (rule of thumb, thinner wire will have higher resistance).
The current will be defined by the camera and will be found on the spec sheet.

Voltage Drop Example (300mA Security Camera)
Here is a quick example:  200 ft. run, 18 Gauge wire, 300mA camera
VD=2 *(200)*7.7 Ω *.3A/1000
VD=.924 V

Voltage Range
Cameras need a certain amount of voltage.  There is normally a range of ±10% of the rated voltage, so for this example we will say that a 12v camera can work in a range of 10.8v up to 13.2v (±10% of 12v is 1.2v). If a CCTV camera gets too much voltage, it will fry, and too little will not power it on.  So if the power supply is exactly 12V at the source, then it will drop .924V in 200ft and supply the camera with 11.076V, which is in the range of operation.

Voltage Drop
 One thing to remember is that the number for the voltage drop is not dependent on the supplied voltage.  So if a 12V camera loses 2 volts, it wouldn’t power on because that is a 17% loss, but if a 24V camera loses 2 volts, it will work because that is only an 8% loss.  So 24V cameras can run farther.
So the final test in for your setup is determining the Voltage percentage drop:
VD%=( VD/Source Voltage)*100

From our example above:
VD%=7.7% (which is in the range)

If the proper power is not supplied to your CCTV equipment, it can cause it to lose signal or in some cases cause your camera(s) to fry!  Two essential things to consider include Voltage and Amperage.
Most of the below data concerning voltage and amperage can be considered for 99% of systems.  Cameras will usually use either a 24VAC or 12VDC current.

Basic voltage & amperage reference guide for proper power supply to your CCTV equipment.

Wiring Tips
All of this stuff is neat and I hope that is explains the science behind it all little more. Just remember:
Longer Run = more Voltage Drop
Thinner wire (higher gauge) = more Voltage Drop
Larger Amps (more powerful camera) = more Voltage Drop
Higher source voltage = Less Voltage Percentage Drop

For Installers
Final point, there are times in which installers have called in because a camera is not working and they claim that the wire is supplying enough volts. The problem with that is that they unplug the camera and connect a Voltmeter to the two wires. The Voltmeter has a very low amp draw, and will show less voltage drop because of that. Once the camera is reintroduced in the circuit, the voltage drop will change, making the measurement ineffective. So we need to run the numbers on paper to determine the drop.

Quick instructions on selecting a power supply:-

The only information you need to have in order to find the correct power supply for your device is the Voltage / Volts (V) and Amperage / Amps (A).

Voltage has to be an exact match. A 12V DC device needs a 12V DC adapter (10% toll).

Amperage is the amount of power your device uses. The adapter you order has to be able to supply AT LEAST the amount of Amps your device draws. If your device states it is 12V 3A, a 3A adapter can handle that load, but so can a 4A and 5A. The higher amperage (amp) power supply will not have to work as hard to handle a smaller load, and will run cooler and more stable. 

If the Amperage of your device is uneven, such as 3.13A or 4.16A, always round up. 3.13A rounds up to a 3.5A adapter, a 4.16A device will round up to a 4.5A or a 5A. 

If you match these two specification (V and A), the power supply will work for your device. 

Detailed Instructions:

In order to find the correct power supply for your device, you will need two pieces of information. These are Voltage (measured in Volts or V) and Amperage (measured in Amps or A). You can find this information off the back of the old power supply, or off the back of the device itself. If you do not find it on the device, you can check the manufacturer's website, or in the device's manual under "specifications".

All of the power supplies we sell are 12V DC. They take any input from 100V up to 220V AC, which is what comes out of your wall socket, and output 12V DC. This is what most digital devices such as LCD screens, DVD players, Hard Drives, Audio Gear, and most other digital devices use. We only carry 12V DC power supplies, so if your unit is not 12 Volt, you will not find the correct adapter here.

Once you have confirmed that you need a 12 Volt power supply, you will need to find out how much power your device draws. This is called amperage. Next to the 12V in the specifications there will be another number followed by a capital "A" for Amps. You will need a power supply that can supply enough power for your device. If your device says it draws 3 Amp (3A), you need to use a power supply that can put out at least that many Amps. If your device states it needs 3A, then you can use a 3A, or 4A, or 5A unit. All will work. 

If the Amperage of your device is uneven, such as 3.13A or 4.16A, always round up. 3.13A rounds up to a 3.5A adapter, a 4.16A device will round up to a 4.5A or a 5A. 

All our power supplies have a connector that is standard for a 12V DC device. Most 12V DC devices use the standard tip. This tip is 5.5mm (outer barrel) by 2.5mm (inner barrel) and is center positive. It is a simple round barrel connector. To repeat, if you match the voltage and amperage, then you should not have to worry about the connector type accept in the rare occasion when your device has an unusual connector such as a double barrel, or a 4-pin, but these are easy to spot as the jack where the adapter plugs in will not be a simple circular barrel with a pin inside. 

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