We took advantage of this at one place where I lived. We had an electric dryer but the house was built for a gas dryer so initially instead of running a 240 volt circuit, we rewired one of the outlets in the room with the dryer to use the other phase and plugged the dryer in using two 120V plugs with hot and neutral going to one and the other hot going to the other. The dryer was also modified to halve the power drawn by the heating element to keep the current reasonable.
They can if that is a design requirement. In most applications there is an assumption that loss at higher power levels is more significant because of cooling requirements; total power lost at lower power levels is always lower even if efficiency drops. The highest power for a given form factor only depends on efficiency at high power.
Converters can also be designed to operate over wide input ranges but this will sacrifice efficiency or price or both. This mostly impacts universal input power supplies. A 2:1 range of input voltage is common but 4:1 is certainly feasible. That could allow a universal input power supply which operates from 60 to 240 volts AC or 85 to 340 volts DC but that still is not enough range to support 48 volts DC never mind 12 volts DC. The implication is that it will be uneconomical to have a power supply which supports both normal voltage AC and low voltage DC. For similar reasons it may be uneconomical for a power supply or inverter to provide high efficiency at the lower end of its power range.
Most homes in the US have split phase 240 with the 240 being used for large loads like environmental control, dryer, range, oven, and now car charging.
Now, however, it's relatively cheap (both in terms of convertors and in terms of loss) to produce DC-DC converters.
There is a reliability issue as well. Converters are more complicated than transformers making them less reliable. If they have to deal with poor power conditions, then they will be less reliable yet. This may be especially pertinent in a home can be expected to last decades before refurbishment.
He's talking about solar DC -> AC conversion: 20% loss, for AC appliances. Then another 20% loss for converting the converted AC back to DC: 40% total loss for connecting to DC appliances.
I was not sure if the article was saying 20% loss for each stage or 20% loss combined but it does not matter; online UPSes which do both conversions continuously often have a 90% or better combined efficiency. I doubt the credibility of the article and author because of this.
Shouldn't there be an option for the battery to generate AC or DC based on the type of appliance that is connecting to it? That would mean 20% conversion loss for DC to AC, for AC appliances, and 0% loss for connecting to DC appliances. The main point is we need both AC and DC sockets connected to this battery.
An easier way to handle this is on the device side but there are issues.
Switching power supplies will usually run on AC or DC without modification. The problem is that the standard voltage doubling input stage without power factor correction expects either 120 volts AC or 340 volts DC. A power factor corrected universal input design will run on 120 to 240 volts AC and 170 to 340 volts DC but this minimum DC voltage is too high to be safe using standard 120 volt AC infrastructure like switches, breakers, fuses, and plugs.
For the next challenge, you will also need to use different, more expensive switches and circuit breakers, or drop back to using fuses.
DC rated fuses are more expensive for the same reason. 250 volt AC rated fuses are commonly only have a DC rating of 32 volts. I usually run across this with multimeters and test instruments which require very expensive DC rated fuses protecting their inputs to achieve their CAT safety rating.
Or just run at 120V DC, as renewable energy systems did (and occasionally still do) before so many appliances were AC-only that it made sense to use an inverter.
Doing this creates an interesting problem. While 120V DC would be fine for resistive loads like incandescent lamps, resistive heaters, and universal motors, switching power supplies without active power factor correction and a universal input range are expecting 340V DC and may destructively fail at low voltages do to their negative input characteristic.
Also, AC/DC conversion isn't as dire as stated. Sloppy cheap converters do indeed operate at around 75% effeciency with the remaining 25% lost as heat. But look at the "80+" computer power supply standards. The "80+ platinum" standard requires 95% efficiency. Those power cost twice as much but "pure science" does not prevent their operation. They work as promised.
The article's efficiency numbers are so far off that I cannot consider the author credible.
Stepping power up and down from AC to DC and vice-versa wastes energy, about 20 percent is lost in the conversion. Some converters do a better job than others, but resolving this 20 percent loss is very important when working on a battery stored energy supply.
That is off by a factor of 2 or more; online UPSes, which do both conversions in series in the same device, regularly have better than 90% efficiency.
Even simpler, you point a laser pointer at the sky, and sweep it manually over a very distant target (bigger than the moon, but further away as well). Clearly your hand is not going to move faster than light, but the point where the beam finally hits something very well might. Again, this intersection is not a "thing", and cannot be used to communicate faster than the speed of light.
A Tektronix 7104 oscilloscope can sweep its electron beam across the CRT faster than the speed of light:
Law enforcement can still conduct an illegal search to further their investigation. They cannot use evidence in court that they directly discovered as a result of the search; However, they can still use the information to help develop their investigation, And once they've found what they think is the truth, they will be able to leverage a practice called parallel construction [wikipedia.org] to develop their case: without needing to make their illegal search or evidence that came from their search part of the case.
The challenge, and the difficulty is.... our legal system doesn't provide any way to challenge actions by law enforcement: there is no way for a citizen to pursue action against the police department.
Which adds up to those being charged with a crime having more civil rights than those who are not. If the police search you without a warrant or probable cause and find nothing, then you have no recourse.
They do not care if other people say they have no legal basis for this, they either don't care, or believe they do have a legal basis for this.
There is basically no way to challenge it so it is legal. If you are innocent, then the court enforced 4th amendment remedy of exclusion of evidence does not apply. If you are charged with a crime, then parallel construction prevents you from challenging the evidence.
Since they cannot be trusted to obey the law, additional legal requirements are irrelevant.
The telecommunication companies are hardy going to implement secure encryption and authentication so it would be better to use end-to-end encryption and authentication controlled by the users. That screws over all lawful interception but if this happens, law enforcement has nobody to blame but themselves for not abiding by the law. End-to-end encryption would also enforce *only* being able to capture true metadata.
Well... if the police stopped murdering people in cold blood as a routine part of their job, we wouldn't have much video to air would we? The fact that there are people that still defend what the police do baffles me.
People have been defending this sort of behavior by law enforcement for decades to centuries.
I spent some time watching trials and it was apparent that when questioned, officers under oath routinely lie and contradicted themselves until finding an answer that the judge will accept. Somehow answering the same question with different conflicting answers never brings their testimony into doubt.
The velocity factor of fiber or copper is between about 0.66 and 0.75 which adds considerably to the delay when distances are large compared to RF transmission through air with a velocity factor close to 1.00. Old style microwave towers with simple modulation schemes were used for circuit switched networks so signal regeneration amounted to reclocking and happened with much less delay than the actual transmission path latency. The equivalent in a packet switched network would be cut-through switching which is pretty rare.
The 17th Amendment did not have much of an effect although I agree it should be repealed. By 1908, 28 of 46 states had popular election of senators and 9 other states required the legislature to take account of popular votes whatever that means so there was already a push at the state level which produced the same result.
The 6th amendment still applies so if no lawyer could be found to represent the accused, a trial could not take place. Of course we regularly ignore the requirements for a speedy trial in the same amendment so it would not surprise me if we ignored this as well.
Many state attorney generals and even attorney generals of the United States have at times declined to defend a law and this practice goes back more than 200 years. When they do this, the court can solicit an interested party to conduct the defense. As a practical matter there is no duty to defend if it is not enforced.
Ex Parte McCardle and the Attorney General’s Duty to Defend Acts of Congress:
Perception may be a different animal, though it's worth noting that the British never resorted to the sorts of tactics they used in Ireland or India to suppress rebellions.
Wasn't it similar tactics which lead to the Bill of Rights?
I wonder how our own no-knock warrants and various other militarized law enforcement tactics compare.
FLIR or TV or laser spot tracker on a surface ship, drone, helo or jet fighter, some schmuck looking through binoculars , IR/Heatseeking sensor on a missile, all become very permanently blind.
Blinding weapons are forbidden by the Geneva Convention so the laser needs to kill them.
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We took advantage of this at one place where I lived. We had an electric dryer but the house was built for a gas dryer so initially instead of running a 240 volt circuit, we rewired one of the outlets in the room with the dryer to use the other phase and plugged the dryer in using two 120V plugs with hot and neutral going to one and the other hot going to the other. The dryer was also modified to halve the power drawn by the heating element to keep the current reasonable.
They can if that is a design requirement. In most applications there is an assumption that loss at higher power levels is more significant because of cooling requirements; total power lost at lower power levels is always lower even if efficiency drops. The highest power for a given form factor only depends on efficiency at high power.
Converters can also be designed to operate over wide input ranges but this will sacrifice efficiency or price or both. This mostly impacts universal input power supplies. A 2:1 range of input voltage is common but 4:1 is certainly feasible. That could allow a universal input power supply which operates from 60 to 240 volts AC or 85 to 340 volts DC but that still is not enough range to support 48 volts DC never mind 12 volts DC. The implication is that it will be uneconomical to have a power supply which supports both normal voltage AC and low voltage DC. For similar reasons it may be uneconomical for a power supply or inverter to provide high efficiency at the lower end of its power range.
Most homes in the US have split phase 240 with the 240 being used for large loads like environmental control, dryer, range, oven, and now car charging.
There is a reliability issue as well. Converters are more complicated than transformers making them less reliable. If they have to deal with poor power conditions, then they will be less reliable yet. This may be especially pertinent in a home can be expected to last decades before refurbishment.
I was not sure if the article was saying 20% loss for each stage or 20% loss combined but it does not matter; online UPSes which do both conversions continuously often have a 90% or better combined efficiency. I doubt the credibility of the article and author because of this.
An easier way to handle this is on the device side but there are issues.
Switching power supplies will usually run on AC or DC without modification. The problem is that the standard voltage doubling input stage without power factor correction expects either 120 volts AC or 340 volts DC. A power factor corrected universal input design will run on 120 to 240 volts AC and 170 to 340 volts DC but this minimum DC voltage is too high to be safe using standard 120 volt AC infrastructure like switches, breakers, fuses, and plugs.
DC rated fuses are more expensive for the same reason. 250 volt AC rated fuses are commonly only have a DC rating of 32 volts. I usually run across this with multimeters and test instruments which require very expensive DC rated fuses protecting their inputs to achieve their CAT safety rating.
48V by itself qualifies as low voltage but does a 48V lead-acid battery system? They operate at up to about 56 volts.
Didn't the proposed 42V car electrical standard use 42V instead of 48V for this very reason?
I consider the 50V standard idiotic; It should have been just high enough, say 60V, so that the telecom 48V standard would be considered low voltage.
Doing this creates an interesting problem. While 120V DC would be fine for resistive loads like incandescent lamps, resistive heaters, and universal motors, switching power supplies without active power factor correction and a universal input range are expecting 340V DC and may destructively fail at low voltages do to their negative input characteristic.
The article's efficiency numbers are so far off that I cannot consider the author credible.
Stepping power up and down from AC to DC and vice-versa wastes energy, about 20 percent is lost in the conversion. Some converters do a better job than others, but resolving this 20 percent loss is very important when working on a battery stored energy supply.
That is off by a factor of 2 or more; online UPSes, which do both conversions in series in the same device, regularly have better than 90% efficiency.
A Tektronix 7104 oscilloscope can sweep its electron beam across the CRT faster than the speed of light:
https://web.archive.org/web/20...
The Soviets made some oscilloscopes which could do this also but they used very long CRTs.
Which adds up to those being charged with a crime having more civil rights than those who are not. If the police search you without a warrant or probable cause and find nothing, then you have no recourse.
There is basically no way to challenge it so it is legal. If you are innocent, then the court enforced 4th amendment remedy of exclusion of evidence does not apply. If you are charged with a crime, then parallel construction prevents you from challenging the evidence.
Since they cannot be trusted to obey the law, additional legal requirements are irrelevant.
The telecommunication companies are hardy going to implement secure encryption and authentication so it would be better to use end-to-end encryption and authentication controlled by the users. That screws over all lawful interception but if this happens, law enforcement has nobody to blame but themselves for not abiding by the law. End-to-end encryption would also enforce *only* being able to capture true metadata.
The R7S721021VCFP is ARM which is good but it has 24 Mbits of RAM arranged as 3Mx8 or 3 MBytes.
To be fair, it takes a lot less than 32 MBytes to support ethernet and an IP stack. Some MicroChip PIC microcontrollers can do it in about 32 kBytes.
I think the sweet spot would be an ARM microcontroller with 256 kBytes or less.
How about a bottomless well with spikes at the bottom?
People have been defending this sort of behavior by law enforcement for decades to centuries.
I spent some time watching trials and it was apparent that when questioned, officers under oath routinely lie and contradicted themselves until finding an answer that the judge will accept. Somehow answering the same question with different conflicting answers never brings their testimony into doubt.
Because two choices which do not represent me are so much better than one choice.
The velocity factor of fiber or copper is between about 0.66 and 0.75 which adds considerably to the delay when distances are large compared to RF transmission through air with a velocity factor close to 1.00. Old style microwave towers with simple modulation schemes were used for circuit switched networks so signal regeneration amounted to reclocking and happened with much less delay than the actual transmission path latency. The equivalent in a packet switched network would be cut-through switching which is pretty rare.
The 17th Amendment did not have much of an effect although I agree it should be repealed. By 1908, 28 of 46 states had popular election of senators and 9 other states required the legislature to take account of popular votes whatever that means so there was already a push at the state level which produced the same result.
http://volokh.com/2010/06/11/w...
But you repeat yourself.
The 6th amendment still applies so if no lawyer could be found to represent the accused, a trial could not take place. Of course we regularly ignore the requirements for a speedy trial in the same amendment so it would not surprise me if we ignored this as well.
Many state attorney generals and even attorney generals of the United States have at times declined to defend a law and this practice goes back more than 200 years. When they do this, the court can solicit an interested party to conduct the defense. As a practical matter there is no duty to defend if it is not enforced.
Ex Parte McCardle and the Attorney General’s Duty to Defend Acts of Congress:
https://www.usfca.edu/uploaded...
Wasn't it similar tactics which lead to the Bill of Rights?
I wonder how our own no-knock warrants and various other militarized law enforcement tactics compare.
Blinding weapons are forbidden by the Geneva Convention so the laser needs to kill them.