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Comment: Re:Even if you go DC, stay at 120V (Score 1) 502

Everything from your wall switches to your wires will cause you never ending problems.

Mechanical wall switches are still rated for DC. Houses USED to be wired for DC a lot. You only have to replace the stuff that was designed after AC was pervasive and wasn't engineered to handle DC.

(I forgot to mention that you'll also have to replace the light dimmers, too, along with most other electronic, rather than mechanical, switches. They usually use a current-zero-crossing turnoff device, and DC won't cross zero unless you force it to do so.)

Even if you replace your wall switches and outlets, your wires will degrade over time and develop holes and other blemishes that will cause a fire.

No they won't - unless they're wet (in which case you have bigger problems than galvanic corrosion). Electromigration at the current densities involved in house wiring is not an issue, nor is insulation breakdown. The wires and fittings will be just fine.

Comment: Re:Even if you go DC, stay at 120V (Score 1) 502

(DANG this stupid touchpad... )

An "inverter", by definition, actually has alternating voltage as a substantial output, or at least somewhere in the circuitry. A switching regulator has a cycling voltage, but it isn't an AC output, or even an AC intermediate.

But they're very similar.

(Also: I was going to mention, above, that the current supplied through the pull-down (or clamp-at-ground) switch is where the extra output current comes from, compensating for the lowered voltage with higher current for similar amounts of power. If the switches, inductors, capacitors, and wiring were all ideal, the driver and sensor circuitry didn't eat any power, and no energy was radiated away as radio noise, efficiency would be 100%.)

Comment: Re:Even if you go DC, stay at 120V (Score 1) 502

A down-stepping DC-DC converter is not an inverter?

Nope. But the pieces of the implementations are similar enough in function that it's close.

A typical DC/DC down converter involves two switches, an inductor, and both input and output filter capacitors, plus control circuitry to sense the output voltage and time the switches. (There may also be a VERY small resistor in series with the inductor to sample the output current if current regulation is necessary, but it's omitted for high efficiency if that's not an issue.) One end of the inductor is hooked to the output cap, the other through the switches to the input cap and to ground.

The pull-up switch is always active (typically a transistor). The control circuitry turns it on and the current in the inductor ramps up, charging the output capacitor at an increasing rate. After a while the pull-up switch is turned off and the pull down switch is turned on. The current through the inductor ramps down, but before it goes through a stop and reverses the pull-up switch is turned back on and the pull-down turned off. The pull-down switch may be a diode, which switches on as needed automatically, but for high efficiency it's usually another transistor, because it has a lower voltage drop and thus is more efficient.

The control circuitry varies the percent of pull-up versus pull-down time to keep the average output voltage at the desired level. The frequency may be controlled or may be allowed to vary somewhat.

So the waveform in the inductor is a sawtooth, and the current never reverses. An "inverter" by definition,

Comment: Re:Seeking Technical Solution to Social Problem? (Score 1) 183

by ScentCone (#49795655) Attached to: Why Detecting Drones Is a Tough Gig

Meanwhile, in ten years, every tourist in DC will have a selfie drone

Which would be fine, except the DC FRZ (flight restriction zone) is a 30-mile circle around the Capital within which it is illegal to fly ANY remote control device of any kind. Includes "drones" as well as those toy RC helicopters at the mall kiosks, and the sort of RC planes that people have been flying around for many decades. Some tourist flying a quad in DC is in for a very rude awakening, as has already happened.

Comment: Re:The things pump out plenty of RF. (Score 1) 183

by ScentCone (#49795617) Attached to: Why Detecting Drones Is a Tough Gig

Yea, but a cell phone signal flying over the south lawn is a pretty clear indicator that you have an issue

Wouldn't matter. Do you understand how small the White House grounds are, and how fast even a modest quad can fly when it means business? I've got one that can do over 40mph. That would cover the distance from the sidewalk in front of the White House to the middle of the typical speech-giving area of the Rose Garden in well under 8 seconds. A drone flying waypoints - with no need for a human controller nearby or watching - could be moving that fast well before it gets to the White House fence, and be coming in 200' overhead, be above a high-profile press event in seconds, cut power and drop like a stone spewing a mist of cesium or a nice cloud of serin or laden with a nice little brick of C4, and it would be on the ground in the middle of that speech/ceremony so fast you'd have no ability to do something about it. Except maybe light it up with some sort of automated buckshot gatling gun, right in the middle of a busy urban area.

This is going to result in a lot more events being held indoors.

Comment: Re:I hate fear mongering... (Score 1) 183

by AK Marc (#49795487) Attached to: Why Detecting Drones Is a Tough Gig
I don't think that would work. After 9/11, the coverage showed unbroken windows removed from the rubble at the pentagon. The windows were designed to withstand a hit from any man-portable weapon system. This included the most powerful sniper weapons, as well as RPGs. I'm assuming the White House is no worse than the pentagon, but I didn't build either.

Comment: Re:I hate fear mongering... (Score 1) 183

by AK Marc (#49795027) Attached to: Why Detecting Drones Is a Tough Gig
So we shouldn't place control on non-LOS 50+ lb drones because there exist 2 lb LOS-only drones? I can put enough C4 on a 2 lb drone to cause problems. The glass on the White House is designed to stop a .50 cal armor piercing sniper bullet. If you wanted to shoot the president, you'd be better off shooting through the wall. But a pound or two of C4 on a small drone, landing at the base of the wall may damage it enough for a clear shot, or dislodge one of the supremely heavy windows. Though I suspect that wouldn't work, for other reasons.

Comment: Re:Impractical (Score 1) 502

by AK Marc (#49794965) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

If the connector was trying to provide 25 amps at 5 volts via the thin little wires, they would arc into gas almost immediately.

My phone charge does 5A at 5V without an issue, and my laptop doing 5A at 20V does so over tiny wires.

As an RV-er, I'm familar with both 12 volt and 120 volt systems. For a LED TV or other low wattage appliance, 12 volt is better, just because it directly comes from the batteries. However, for a load like a microwave, A/C, heater, or anything above 300 watts, trying to run that on 12 volts would require very fat, expensive cable.

You answer the question, then immediately forget the answer. You have AC at 240 (sigh, 110, if you must) and have outlets in some strategic areas (kitchens and for major appliances), and 12V or 48V everywhere else.

I think we should have a 48V internal wiring standard, with some 240V appliance plugs, for vacuums, refrigerators, washers and driers, and such. The dual-standard will complicate things slightly, but result in a large overall savings, as wall-warts are eliminated, and all their waste.

Comment: Re:Premature (Score 1) 502

by AK Marc (#49794893) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage
More sense is 240 AC for appliances, and 12V or 48V for everything else. DC-DC stepping in the wall jack isn't hard. So you go to the jack at 48V, and there to 5V for your wall-wart voltages. With some for 12V or 48V for higher powered things.

If it were me, I'd design a mechanical switch in the plug that activated the circuit, so it would have zero loss when not used, unlike current wall warts. We use 110 VAC because it's what we've always used, not because it's a good voltage or current type.

Logic doesn't apply to the real world. -- Marvin Minsky

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