Greetings Jim,
I read Redclay’s letter on his questioning using electronics with generators. Ham (Amateur Radio) operators have been using various electronic devices for years powered by generators. The use of power sensitive devices such as a computer on a generator is fine if you take some precautions. First off the generator is what I called a “spiky” power source. So to smooth out the power supplied to the electronics one wants to use a good spike/surge protector between the generator and electronic devices. Do not skimp on cost and quality here. In my opinion it is preferable to use a battery backup with built in surge protector between the generator and the electronics. Usually the battery backup systems have a more responsive circuit for smoothing out power when it spikes as well as providing protection for a wider range of spikes and electrical anomalies. An additional benefit of using a battery backup is that when you have to turn off the generator for refueling, etc. you can continue using the electronics (radios, computers, etc.) while refueling. The length of time you have on electronics use depends on the rating for the battery backup system and what you have hanging off of it. The average time we had when refueling during Field Day was up to 20 to 30 minutes. We added an additional layer of protection by adding a power strip with surge protection between the battery backup and the electronics. This allowed us to cut power at the strip when shutting down or starting up the generator. I am just paranoid that way because having worked in emergency communications and various computer fields I have seen electricity and lightning do things to equipment that one would not normally expect. An extra layer of protection doesn’t hurt anything. Surge and spike protectors are rated in terms of ‘joules’ of protection. A protector, with or without battery backup, that is rated for 1,000 joules is more protection than one rated at 400 joules. So look at the ratings on the surge protector to give you a benchmark for comparison. Battery backup systems are also rated in terms of wattage also for the maximum amount of load you can place on the battery backup and the subsequent amount of ‘up’ time you will have for your electronics. Keep in mind that the more load you place on the battery backup the less time you have. And if you use a conventional CRT monitor, you will be pulling more than using say a LCD monitor. The same difference applies between a desktop computer vs. a laptop, generally speaking. I have seen some high-end laptops pull more than a moderate desktop system. So size your battery backup accordingly. If you want to learn alternate ways to power emergency communications equipment off grid, attend a ham radio Field Day. You can find a varied array of methods. And who know you may get the chance to see a real time emergency and how the ham radio community provides an emergency service. One Field Day I was working turned real when there was an earthquake in California. We were contacting a station there when we heard the emergency call. The other operators and myself found ourselves relaying information to emergency services in [Washington] D.C. and at, oddly enough, the UN. We didn’t think that the UN participated in the ham activities, but on that day they did. Whatever shortcomings the UN has, on that day they did provide a real service to the U.S.
Naturally a surge protector of any rating will not protect against a direct lightning strike. Lightning will go where ever it wants to. There are lightning arrestors made for antenna line but the operative word here is ‘arrestor’. It attenuates the strength of the lightning. And if you are lucky enough, and have unplugged all electronics and associated antennas you may have workable equipment after the strike, but that is no guarantee. I watched a bolt of lightning strike a friend’s house. The bolt of lightning hit his 30 foot tall tower, traveled down the tower and into his house. At every grounding point along the way there was a scorched patch of grass where the bolt was bled off. When he got home the smoke detector was going off and the smell of burned electronics hung heavy in the air. He had unplugged all antennas, and power cords leading to his radios and computer prior to leaving. But (knew that was coming) his independent radio power supply was still plugged into the electrical outlet. The lightning charge jumped the power supply and arced from one piece of equipment to the next and finished at his computer. His computer monitor had caught fire and the plastic case had melted down inside the circuit board and put out the fire! Definitely it was Providence that kept his house from going up in flames. Moral of story: Surges and spikes can be defended against (two different power anomalies) by using a good surge/spike protector. The only defense for electronics from lightning is to unplug everything from any conductor. Then you may have protected your equipment.
lightning protection for homes is something I haven’t seen on any modern built homes. I remember my grandmother’s farmhouse festooned with three or four lightning rods. Her house sat near the top of a hill. And in those days when it was built (early 1900s) every house on open ground or on a hill had at least two lightning rods. Old Ben Franklin knew his lightning and provided a method for protecting buildings. The lightning rod is simple a device with a metal rod several feet long with a glass ball at the base and a copper or copper clad grounding line going about eight feet into the ground. These were on almost every old farmhouse I have seen. So the lightning rods would either discharge the air surrounding the house, preventing a ‘lightning strike’ (most lightning is from ground to air, not air to ground). Or if the charge built up too fast and there was a discharge of electrical energy the rod would take the hit thus mitigating or eliminating damage to the structure and the subsequent fire that usually follows. Remember lightning temperature can be hotter than the Sun’s surface! If I had a home, modern built or otherwise, in the open or near the top of a hill you can bet there would be lightning rods to help. That is not to say the rods will stop all strikes, but it is the attenuation of the energy is what you are going for. I remember several discharges on the rods at my grandmother’s house during violent thunderstorms. It reminded me of Shakespeare’s quote, “..the sound and fury that signifies nothing…” It was loud, it was bright, and it scared the ‘yee-ha’ out of us grandkids. But when we went to look at the damage after the storm, there was none; save the newly fire polished segment of the lightning rod. I am usually befuddled when a home gets ‘hit’ with lightning and the homeowner wonders ‘how this could happen’. Lets see, home on a hill or open area where it is the tallest object plus thunderstorm, the home is not properly grounded…well duh!
Perhaps ‘modern day’ construction has disregarded the use of a good lightning grounding system because contractors and the like figure it is ‘too unsightly’. But a house that is a burned out shell as a result of a lightning strike is more so. And maybe modern science has proved that lightning rods are no longer a viable form of protection. I may have to research this. But for their day they sure seemed to work quite well. Other areas of the country may still favor this protection. But here on the East Coast they have all but disappeared from any building save the occasional ‘old time’ farm house scattered here and there.
Lightning can be detected before it becomes a direct hazard. Many years ago I took part in a NASA project called Inspire. It was geared toward gathering VLF (Very Low Frequency) radio waves produced by lightning and man made VLF signals from a [Space] Shuttle experiment. The experiment recorded the ‘sound’ generated by generated VLF ‘footprint’ as the Shuttle passed over in orbit.
The occurrence of VLF with lightning allows for a method of detecting the electrical charge of an approaching thunderstorm. I wonder if it is not possible to detect an EMP before it hits and area. Logically it would seem so. If an electromagnetic pulse (EMP) generates a VLF signal which precedes it as does lightning then there may be a way to give a heads up warning of a few minutes. Whether that would allow time to disconnect any devices would have to be tested. But as lightning travels at or near the speed of light and does give and ‘advanced footprint’ far ahead of the approaching thunderstorm, and is detectable. So would a ‘lightning detector’ have the sensitivity range to detect an approaching EMP? The only way to know is to generate an EMP and see if it produces a VLF at all, and if so is it within the range of a ‘lightning detector’? And if it is in range or the detector’s sensitivity could be adjusted within it’s circuit could the detector distinguish between an EMP and approaching thunderstorm’s electrical energy? As usual, more questions are created than are resolved.
For info on how surge protectors work, see: Howstuffworks.com
For info on a commercial lightning detector. I have no interest in the company but its one I picked at random: See:http://www.boltek.com/
Here is some info and circuit design for ‘do-it-yourself’ project from a ham operator.
For more information on lightning detectors available do a web search and you will find all kinds of plans, and complete units. – The Rabid One
Letter Re: Of Computers, Generators, Power Anomalies and Lightning
