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Comment Re:He wasn't able to give it up. (Score 3, Interesting) 343

AC by virtue of alternating, passes though zero current flow and zero voltage 120 times a second in this country. When you have an arc, you are passing an electric current though a plasma and that requires that you keep it hot and ionized. It is the current that keeps the plasma hot and ionized.

As a switch contact opens, initially the distance between the contacts is under the flash over voltage and an arc of plasma is formed. This arc requires current to keep flowing though it to be maintained and as the contacts separate further the resistance of the plasma path increases, lowering the current. Eventually in AC circuits, the voltage needed to maintain the plasma path starts to cycle under this minimum value for longer and longer times and current starts to fall off on average. This falling current, makes the arc plasma start to fade and will eventually extinguish the arc during the times when the current and voltage cross the zero level.

DC has no regular fall off in the plasma because it is always there, full on, full current. This means that switching similar voltages and currents in DC requires additional distance over AC. DC starts the arc and builds the plasma without stopping and only the resistance of the plasma as the distance increases is what will cause the current to get lower and lower until the arc extinguishes. There are no "off" times like there is in AC so the arc exists over a larger distance.

ALSO, on very high voltage AC circuits, it is possible to disconnect the circuit during a zero crossing. In that case, assuming you can get the contacts far enough apart to avoid flashing over, there never will be an arc to start with. Even though it's mechanically difficult to move things that fast, they sometimes do this kind of thing to suppress the arc in AC. This doesn't work in DC because there is never a zero crossing.

Comment Re:Outdoor (Score 3, Informative) 343

they still work but at a much reduced capacity so if you had double the panels you usually require, you should be ok-ish.

Oh ye of great faith and frail engineering ability...

What are you going to do? Buy twice as many solar panels so you can charge your battery to hold you though the night? And as the original poster said, you planning to live without electricity for 6 days when the sun is behind the clouds for a week?

There are ways to make this work, but you have to understand that you will have to pay for capacity you don't usually need in both your batteries and solar panels and then still accept that there will be times you will run out of power. Plus you will REALLY drive up your cost per watt. I'm thinking you will likely pay about 4x what it costs for just a daytime system that carries your needs when the sun shines. You will need more than double the panels and add batteries to carry your load for a specific number of days.

If you want a week of "standby" for that rainy week, then you will need 7 days of battery capacity (ouch) plus enough additional collection capacity to charge these batteries. Say you want to recharge in 3 days, then you will need to have 2.5 times the panels it takes to carry your load for a day (plus the original panels that carry you a day). So for a system with 7 day backup and 3 day recovery, you will require 3.5 times the original collection capacity and enough batteries to hold 7 days of use.

Solar is not competitive economically when you are not talking about charging batteries. Going totally off grid requires significant investment in capacity BEYOND just your daily needs, unless you don't mind being in the dark pretty often and then the costs multiply, making an already bad ROI much worse.

AND I would like to mention that MOST batteries have losses when you charge and discharge them, some being as high as 30% losses... Just think about how many more solar panels you will need to buy for this scheme.... It's going to be nearly 4 or 5 times as many.... Good luck making that pay..

Comment Westing House.... (Score 1) 343

Mr. Edison is that you? I thought you died decades ago!

Look, first off the efficiency argument is garbage when you are comparing apples to oranges. If you want to say 100 Watts of power from burning coal, then start to compare how much power your cell phone uses, you have pretty much stepped off the reservation engineering wise. You are talking HEAT in BTU and then electrical power out? Two different types of fruit.

To convert BTU heat into electricity requires a heat engine that takes heat and turns it into mechanical rotation. Thermodynamics demands that even an ideal heat engine has losses, so if you want electricity, that's a price you pay. Our power plants that use heat all pay the same price, and for the most part they are all darned near ideal, even though losses might approach 30% of BTU in to BTU out if you look at it that way, but remember, you still want/need electricity.

Now this author is correct in saying that if all you want is HEAT, then using electricity as a way to transfer energy from a stack of coal over a long distance to your electric stove, vast improvements are possible by burning the fuel locally. However, if you want electricity for running that cell phone or that TV or even that heat pump (air conditioning unit) then burning coal locally doesn't help you at all.

BTW, the electric grid is amazingly efficient given what it does and how much power it transfers around every instant. It's far from perfect, but it's not a huge energy waster. Complaining about this inefficiency is like complaining about a leaky roof getting your furniture wet when it rains while your home is flooded up to the rafters by the river next door.

Comment Re:How to do 500 feet? (Score 1) 53

I am assuming they mean above ground, because otherwise it would be a stupid idea (I'm not saying that's impossible). Do you require drones to be equipped with laser or radar altimeters? Do you require them to use DTED?

I would expect that they would be happy with the following rule.. The 500' altitude restriction referenced from the GROUND level at the point of launch. I would further use a 1 mile radius from the starting point as a limit. The only other way this works is you have and are following DTED and do not exceed 500' above an adjacent DTED observation point, which doesn't seem practical to me.

Comment Re:When guns are outlawed... (Score 1) 53

Although not desirable, I don't see why a small hobby drone should bother a full size airplane. The plane should just plow through on its course and it will easily knock the drone out of the sky. A bird would have more effect than a small drone, and no one is talking about geo-fencing birds. On the other hand, my kickstarter project of dog fighting drones should do well. Killer drones to take out the unapproved drones. All government areas and rich celebrities will want them.

This is the FAA we are talking about where perceived safety is king... Where it's not likely to kill anybody, shooting at an aircraft is illegal... Why? Because it MIGHT kill somebody, or a whole lot of somebodies if you hit the thing with your lucky shot.

Drones are the same kind of thing. Yea, it's unlikely a drone is going to bring down a 747, even if it happens to hit it, but it's POSSIBLE one could go though the windshield or though an engine and do enough damage or cause enough distraction to cause a crash that kills somebody. The FAA is about safety, and they do that by elimination of as many risks as possible and leaving as much margin for error as they can. In this case, eliminating the risk is EASY, just forbid flying hobby drones in the same airspace with aircraft which this 500' ASL and 2 miles from airports. If they are never in the same airspace, there is no risk.

Comment Re:Don't buy the cheapest cable (Score 1) 377

If you don't know enough about what you are buying to KNOW if the cable's specs are good enough to work, then you deserve to be fleeced. If you are not willing to take back something because it didn't' work, you are asking to get fleeced... If you don't have time to fuss around, then just pay or installation and let the installer choose what you get (and will pay though the nose for).

I'm cheap. Personally, I use the "junk" HDMI cables at home and I get them for about $3 each when the local electronics retailer puts them on sale. Now I don't have ANY equipment that needs anything better than HDMI 1.1, but we've already established that for home use, I'm decidedly cheap. I work hard for my money and I'm not going to throw it away on something I can do cheaper.

Oh, and I've actually NEVER had a cable issue with any of the cheap HDMI cables I own. Like it or not, most of these things come off of the same few assembly lines in China now so for the same spec, one is as good as the next for the most part.

Comment Re:Passed data with a ton of noise? (Score 1) 377

Oh, and one more thing, before I go..

Ethernet cables are transformer isolated at EACH end of the cable. Unless you are using CAT-6 shielded wire, the ground loop thing is generally rubbish as CAT-5 carries no ground or shield.

Now if you ARE using CAT-6, then you may need to worry about breaking the ground loop by disconnecting (isolating) grounds between pieces of equipment, I suggest you just break all CAT-6 grounds at the remote equipment and let the local safety ground in the wall plug serve for that. Now if that's a problem, you have a larger grounding system issue and will need to create a "signal ground" using some really low impedance cabling, start putting in isolated ground receptacles and paying very close attention to both the electrical code (for safety), isolating equipment from the racks they are in and establishing a set of "wiring rules" that avoid ALL Ground loops.

I've only seen ONE installation where the grounding of equipment was over complex, and it had multiple studios (8 total), where we had the top FM station for the market and produced and fed state and national news casts for smaller stations in the network. This was all on the 2nd floor of a building and we had a "signal ground" system of a dozen ground rods, wired together using multiple runs of 00Ga stranded welding cable. EVERY power outlet was isolated, every piece of equipment had a single low impedance connection to the signal ground and how all this happened involved a pretty complex set of rules. It was actually MY job to install all that stuff, so grounding is a subject I'm fluent in, or at least I was..

Comment Re:Passed data with a ton of noise? (Score 1) 377

I would say your "specs" are a bit different than the home audiophile's.

I fully get durability may be YOUR primary concern, in which case you want a cable that will work after being used and abused. For you, the connector quality, how fast the wire work hardens and breaks, and strain relief build are very important. But for most audiophile's, the issue is "how good does it sound". They are all about "my system sounds better because I used better components" and because they don't muss around with stuff all that much, durability is not that important.

Vendors prey on this "if it costs more it's better" mentality and sell essentially the same cable, off the same assembly line that meets the same specs in different packaging. That "monster cable" 10Ga stranded speaker cable really isn't twice as good as what you can buy from a home improvement store or even cheaper from an online retailer that sells 10Ga stranded wire. You can pay $100 or more for that name brand 10Ga stranded, or do the same thing for $10 (plus shipping). Audiophiles are routinely "sold" stuff (cables, power conditioners, components) with brand names that sound better, but where the specifications of the cheaper option are the same or better. This is most true with cabling..

Comment Re:Don't buy the cheapest cable (Score 1) 377

I don't agree... You use the cheapest cable that operates as you want it to...There is absolutely no value in buying a "better" cable over the cheap HDMI cables in the bargain bin if both work.

If you don't need HDMII 1.4, and 1.1 suits your purpose, by the cheap 1.1 cable. If there are two 1.4 2 Meter cables and one is $40 and the other is $1.99 buy the cheap one. If the vendor is selling crap, take the cable that doesn't work back for a refund.

If you are worried about future applications of the cable, DON'T bother unless the "future" is pretty close. Electronics and advanced cables *always* get cheaper over time and it's rarely cost effective to buy more than you need now, over replacing it later.

And yes, one of my primary jobs is system integration. I design and build complex racked systems in the telco space which are high availability (5 nines) call processing platforms. So I professionally make cost verses durability decisions. In a home AV system, for the digital cables, cheap is just fine. What suffers is durability, but most home AV systems are not high vibration, and usually get upgraded often anyway.

"What people have been reduced to are mere 3-D representations of their own data." -- Arthur Miller