CENTURION vs. Nature

Mother Nature is a notoriously fickle – and at times downright ruthless – dame. While she may occasionally do something whimsical like giving us a monkey’s wedding, there are also times that it’s quite evident that she’s had a fight with her boyfriend or something. This year especially was fraught with meteorological curve balls including, but not limited to, tornadoes. Freaking. Tornadoes.

It’s also starting to become pretty clear that Al Gore was onto something with the whole global warming thing. According to NASA’s Goddard Institute for Space Studies, Earth’s overall temperature has increased by 0.8°C since 1880. While this may seem insignificant, the effects are dramatic and far-reaching and, regrettably, climate change is showing no signs of slowing down.

Earth's overall temperature has increased by 0.8 degrees centigrade since 1880

While there’s not too much that we can do about the weather, we can set your mind at ease by telling you that CENTURION products have been designed to handle very extreme environmental conditions.

According to senior electrical engineer Tony Baia, reliability as a design philosophy and something to be sought with relentless fervour has been ingrained in CENTURION’s DNA since the very beginning.

CENTURION senior electrical engineer, Tony Baia

“From its inception,” begins Tony “Centurion Systems’ founding fathers and design engineers understood that, to ensure the reliability of its now-famous D5 [sliding gate motor] and other electronic products, they had to tame one of nature’s most awesome and powerful phenomena: lightning”.

Lightning has for long been the bugbear of electrical appliances, the lure of so much sweet, conductive metal in one spot simply too much for heaven’s own electricity to withstand. It’s a siren song as old as time, but the tune is no easier to hum along to. Every year, insurance companies pay out millions in lightning-related claims, and some firms do not compensate for lightning damage as it’s seen as a vis major.

“With this in mind,” continues Tony “the design engineers approached the CSIR [Council for Scientific and Industrial Research] and other institutions who had the equipment and knowledge to tame lightning.

“A cost-effective and highly efficient circuit was designed that has remained with Centurion Systems to this very day, ensuring that our control cards continue to function when other equipment has failed”.

Tony provides a detailed description of the kind of technology that goes into such a sophisticated and robust piece of equipment.

“CENTURION uses a layered approach to protect against lightning; all inputs exposed to the outside world are protected by multiple components”.

Layer 1

Right up front is a high-power resistor that absorbs and slows down the lightning surge.

This is followed by a Zener (analogous to a clamp) that prevents the lightning-induced voltage from going above levels that are harmful to the rest of the electronic components on the PC board.

Layer 2

The lightning-induced voltage sometimes climbs much faster than the Zener is able to respond; to further protect the sensitive electronic components, another capacitor and resistor are used to slow down the rising voltage allowing the Zener time to respond and clamp the harmful voltages.

Layer 3

The TRG [trigger] input is the one that is most exposed to lightning surges due to it having the longest connection length – this connection could run from the gate motor all the way to the indoor intercom system.

To ensure that this input has even more protection against lightning surges, a gas arrestor is placed in front of the high-power resistor to further absorb the energy of the lightning surge.

Level 4

To protect against lightning surges, the energy that is being absorbed by the abovementioned layers needs to find a path to earth or ground; to achieve this, another gas arrestor connects to the mains power supply earth.

Level 5

CENTURION power supplies like the CP84SM have an earth tab that connects to an earth spike, allowing the lightning surge energy to find a very quick and easy path to earth, thereby avoiding damaging the sensitive electronic components on the control card.

Layer 6

The power supplies like the CP84SM also have protection against lightning surges coming down the municipal power lines. These take the form of metal oxide varistors, or MOVs. MOVs limit the voltage supplied to an electrical device by either blocking or short-circuiting to ground any unwanted voltages that are above a safe threshold.

“Lastly,” Tony concludes “it must be remembered that, if the lightning surge is too powerful or too close to the gate motor then something has to give. That is when most of the components referred to above will be damaged, sometimes leading to unseen damage of other components on the PCB”.

In addition to superior lightning protection, CENTURION operators boast a number of sophisticated design features intended to moderate Ma Nature’s onslaughts. These include:

• · Insect-ingress protection – insects are a big problem throughout continental Africa
• High water-level lines for reasonably good immunity to flooding
• Black-out and brown-out failure protection – CENTURION’s products are purpose-built to address these classically Third World-type infrastructural problems

How important is proper earthing?

We often get asked the question: how important is it to earth one’s gate motor (or other access control device), and what will happen if it’s not properly earthed? In this article, we’ll attempt to answer both of these interrelated queries in as simple terms as possible.

But first, a quick lesson in elementary physics.

For all its many uses and myriad benefits to the human race, electricity, as a rule, is still a bit on the lazy side, and it will always look for the path of least resistance. It’s sort of like that kid (read: me) who always got picked last for the softball team and would simply drop dead halfway through an obstacle course, a half-consumed hot dog in one hand. When an electrical surge takes place, there’s a build-up of charge, and all those extra electrons need to go somewhere. Think of it as being at one of those family gatherings where, one moment you’re standing talking to your favourite granny, and the next you’re drowning in a sea of distant aunts and cousins. Things can get pretty crowded for our friends the electrons, and the earth provides a large surface where they can be dumped and be spread out. That’s why we refer to a circuit as being “earthed”.

With regards to lightning, the mechanics are pretty interesting, if not fully understood. What happens is that electric current builds up within the thundercloud (caused by bits of ice bumping against each other like nature’s bumper cars), and the positive and negative charges start to separate. The positive charges are lighter and float to the top of the cloud, while the negative charges sink to the bottom.

This lends credence to the belief that positivity will get you to the top while negative thoughts will just drag you down.

During a thunderstorm, the ground beneath the thunderclouds tends to become positively charged, and there’s attraction between the negatively-charged clouds and the positively-charged earth. This fiery love affair makes itself known to the world through, you guessed it, lightning. It’s pretty romantic, don’t you think?

So, what does your gate motor have to do with it?

Again, it all comes down to the path of least resistance. Cables, wires and even electronic components generally contain copper, and copper is a conductor (a material with a very low resistance) so it makes sense that the current would want to take this nice, easy shortcut to its destination, the earth. To the electrons, it’s like being lathered in sunscreen and going down one of the waterslides at Sun City. During a lightning strike or power surge, very high voltages are generated and these voltages may very well find that their quickest route to ground is through your gate motor, an appliance which has not been designed to deal with such excessive voltages. If there is no earth return path, the extremely high voltage could end up destroying your gate motor’s electronics or, in extreme cases, even cause it to catch alight. Yes, we have seen firsthand what happens to gate motors that haven’t been properly earthed, and it ain’t pretty.

What does a proper earthing system look like?

Remember, the charge is looking for that sweet, sweet shortcut, and it’s up to you to provide it. Connecting your gate motor’s earth wire to a copper earth “rod” or “spike” (via one of the securing bolts) will provide a solid conductor through which the high voltage can travel to ground. You can also connect an optional surge arrestor for additional lightning and surge protection.

Gate motor lightning protection

Lightning season is upon is (if you live in the Southern Hemisphere, anyway) and, as is sadly often the case, electronic devices will be taking a beating and by extension, so will our bank balances.  Replacing lightning-damaged equipment not only takes a considerable monetary toll (especially since vis major or so-called “acts of God” are not covered by most warrantees), but comes at a great cost to our convenience as well.  Gate motors may not be exempt, but there are some ways of minimising the chance of a lightning strike or at least minimising the damage that ensues.

1.       Proper earthing

This is arguably the most important point to consider with regards to lightning protection.  If you’ve ever taken a high school science class, you should know that electricity always takes the shortest route to ground, and an unprotected gate motor may well provide a lightning bolt with the ground it seeks.   Therefore, it is of paramount importance that you connect your gate motor to a suitable earth point, such as the track that the gate runs on.  Earthing can further be improved by installing an “earth spike”, which is essentially just a metal rod, next to the motor.  It is far more likely that lightning will strike this rod, as the rod provides it with a more stable earth.

2.       Surge limiters

There are some very effective products on the market that can be connected to a gate motor’s power supply and provide it with a means of “clamping” the excessive voltages induced by lightning and power surges.  Of course, these surge arresters will not prevent lightning from ever hitting your gate motor but it should at least minimise the amount of damage that it causes to the electronics.

3.       Built-in lightning protection

Gate automation companies are well-aware of the risk that lightning poses to electronic equipment, and as such much attention is given to the design and integration of onboard lightning protection.  Nowadays, most gate motors come standard with gas arresters and other surge-limiting components to minimise the damage caused by lightning strikes.  Again, the idea here is not to prevent lightning from targeting the motor (the person who invents such a means will be an instant millionaire!) but rather to protect the most vital components.

4.       Take preventative action

If the weatherman reports that a storm is on the way, it is always wise to unplug sensitive electronic devices.  This may cause some short-term inconvenience, but will save you a lot of heartache (not to mention cash) in the long run.