Lightning, Cameras, Action…

Lightning, Cameras, Action…

Contributor: Video Experts

It’s your choice, a happy ending or a real shocker!

Lets face it, I don’t think any installation out there could withstand a direct hit, it’s the voltage surge or spike we have a chance to prevent. I will list and discuss some typical installation problems and their corrections.

There are four levels of component failure associated with “over-voltage”, the first and most severe is non-repairable board failure. This usually is still smoking by the time you arrive and any repair attempt (if not in vain) would and most probably will fail in the near future. As almost all of the components on the board have been “touched” by the surge, and their values altered which will cause premature failure if not “buggy” operation.

Close up of a

Close up of a “hit” communication chip. Leads are vaporized and damage had spread to other sectors on the board.

Next is singular component failure, where the servicing technician has evaluated the circuit surrounding the failed component and has deemed it untouched by the over-voltage.

The chip has virtually

The chip has virtually “popped”. The damage surprisingly had been contained to the single component and the main board was saved.

It’s very important to check even the substrate (board) around the circuit as traces can be carbonized and become resistive.

This is a diode, still intact, but its leads are

This is a diode, still intact, but its leads are “carbonized”. The feed through (arrow) connects to the “inner” circuitof the board and the circuits resistance had increased, leaving this board unsalvageable.

Nearly the most common failure and I don’t think lightning is always the culprit, is the fuse at the power input. This seems like a no-brainer, but its possible that the blown fuse is caused by the equipment’s internal circuit drawing excess current due to failing components and or increased resistance from prior events (surges).

The most common and least expensive is software failure. This can be easily corrected by re-initializing the equipment. A reset should always be attempted before calling for service, as mostly all equipment is subject to voltage fluctuations, resetting should not be considered a failure more rather a nuisance.

Now for the steps of prevention.

Use a ground wire when connecting your power lines. Most equipment manufacturers incorporate some kind of over-voltage protection in their designs. This is rendered useless if the equipment is not grounded to earth, as the spike needs an escape route away from your installation not right into it. Think of the current as a fast flowing over-flooded river, it will follow the path with the least resistance and crash through banks it not provided with a path. That means make sure your grounding wire is well connected or bonded to a known earth ground and it’s of adequate gauge.

Verify that all exterior coax cable runs are laid as straight as possible, try to avoid any bends less then 90 degrees, and never leave excess cable coiled or bundled on the exterior. Be sure all coax cable entering from the outside, passes through some kind of surge protection device before it reaches your installation. The simplest and least expensive way is a connection block that splits the cable before it’s entry point and offers you a tap to add a grounding wire. This is not the maximum protection you could provide, there are much better (and more expensive) units available, but it will work.

When installing lines (power, control, video and communications.) in a suspended ceiling and are not using conduit, stay at least 12 inches away from fluorescent light fixtures and any high voltage cables. Make sure that your installation doesn’t share the same circuits with any large inductor loads such as HVAC equipment, elevators, compressors or any large motors. Generators have also been known to cause problems time to time. If a common circuit must be shared with such equipment, be sure to use an isolation transformer with an additional noise suppression device.

Remote applications if in separate buildings, or on different power mains, should share a common ground and the remote unit should be powered through an isolation transformer. We see a high number of comm. chip failures during the summer, that in turn slow down when the lightning season has passed. The diagram below could explain the phenomena.

Example of how nearby lightning strikes destroys communication chips in
equipment involved with remote control.

Example of how nearby lightning strikes destroys communication chips in  equipment involved with remote control.

Example of how nearby lightning strikes destroys communication chips in
equipment involved with remote control.

1) Lightning strikes the ground in figure1. The energy radiates through the ground in a fashion similar to that of a large wave.
2) The “wave” hits building #2’s earth ground well before it reaches (if at all) building #1’s ground. At that moment building #2’s power grid goes high as it’s ground is elevated possibly hundreds of volts.
3) The communication lines between the two buildings in figure 2 experiences a huge difference in ground potential, and blows the comm. chips in both units.

A possible solution to this potential problem, as an example using a matrix bay as the main unit in building #1 and a keyboard as the remote unit in building #2, would be to isolate the remote keyboard from building #2’s power grid and to bond their grounds together as follows.

Power the remote unit with an isolation transformer and at the same time run an extra ground cable from building #1, using the same ground reference as the matrix.

Supply this ground at the secondary side of the isolation transformer used to power the remote keyboard in building #2.

Now the two units even though in separate buildings share the same ground reference, thus eliminating any difference in ground potential.

In this example I used a matrix bay with a remote keyboard, but the same rule applies to PTZ cameras and or anything using communication lines for control.

Now that you have harnessed the lightning threat, next storm kick back and enjoy the show!

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