>> >First, to get common names:
>> >Hot = one Phase
>> >Neutral = Protective Ground
>> >Ground = Ground (the starpoint on 3 phases connected to earth at the
>> 'generator')
>
>> That explains the confusion. In the US:
>> Hot is one phase and in single phase systems you can and do have 2 hots.
>> Neutral is what you are refering to as ground. The starpoint for both
>> single and 3 phase.
>> Ground is the protective / frame ground.
Yes. In the UK, "Hot" is usually referred to as "Live", and until 1992 this was
the official term. In 1992 the term was changed to "Line", so that the phrase
"Live parts" could be introduced to mean any conductor connected to the
electrical supply (i.e. not including the protective ground, which is called
"Earth")
>> >Second, do I understand that US appliances got fuses on both wires
>> >and both are switched ?
>> On 240 volt equipment yes.
>
> Ahh ja - we also use fuses in each 'Hot' wire - so if you have a
> 3~ installation, 3 fuses are to be installed _and_ they have to
> be tied (mechanical), so if one blows all 3 will go off.
In the UK it is similar, although I don't think there is a requirement for fuses
to break all three phases for a fault on one. Since the US has many 240V
centre-tapped-to-ground installations, 240V would have fuses in both lines (both
hot) but none in neutral. ISTR the neutral wire in some 240V equipment (cookers
are an example that springs to mind) is used instead of protective ground, which
makes me a little uneasy.
>> >Over here in Germany only one wire is
>> >switched and protected with a fuse, althrough it is not defined
>> >which one is the 'hot' line, since our connector is symetrical
>> >- there is no way to insert the plug in a way where the Hot and
>> >the Ground side is defined - Our plug isn't inherited from the
>> >DC times, but rather a new design when 220V AC became standard
>> >in the 30s, to fit the needs of (and only of) AC Eq.
Hans, I think you've gone some way to answering your own question here. See
below.
>> The US did not used to make a distinction between hot and neutral until
>> about 30 years ago when they added the "protective" ground pin. Now they
>> are keyed. If you look closely at a receptacle, one blade is wider -
>> neutral, The narrower blade is Hot and the round pin is protective ground.
>> Some "equipment" uses only 2 wires. The blades and often one is larger to
>> assure that it is polarized correctly. These polarized plugs have come into
>> common usage in the last 20 years.
Ah. That explains some sockets that I saw when over there last year.
> Strange, but common - I don't know any reason why the system has
> to be keyed, I always assumed the US development of keyed plugs
> was triggered by old DC systems (since in DC Eq. it is necersarry
> to know the orientation), but not a new addition. Strange, we
> dropped all orientationwhen switching to AC (with Protective
> Ground). Could anyone give give a reason why the system has
> to be keyed _IF_ a Protective Ground is included (other than
> define the Protective Ground pin) ? Because, without Protective
> Ground a definition of Neutral is essential, but with, no longer.
Because the fuse and/or switch _in the equipment_ has to be on the hot/live side
of the supply. Otherwise a blown fuse - because of a short circuit - could
leave the equipment with the hot supply still connected to whatever shorted out.
Which could be the chassis...
Also, at least in the UK, some old equipment had neutral solidly bonded to the
chassis and no protective ground. This is common on valved (tubed) radios and
things. ISTR that here the fuse was generally on the chassis side, so that when
the fuse blew, the chassis would no longer be connected. Still not really safe,
since the chassis would be connected to the other side via the heaters of all
the valves, and these typically pass 100mA to 300mA at mains voltage, or more if
they're cold.
Philip.
><>that were clearly under 1.4kw. The codes are aimed at providing reasonabl
><>power. Here a 15A/115v is the nominal and 115V/20A is a max
><
><No, it isn't. I have several 115V 30A circuits in my computer room -
><this being an extremely common rating on the power controllers used
><in smaller DEC systems - and looking at the codes and the Hubbell catalog
><it would seem that 60A circuits are standard things as well.
>I should have qualified that as common residential and business circuits.
I would call 115V 30A a common business circuit; it's certainly exceedingly
common on minicomputer power controllers. What else do folks plug the
Twist-N-Locks on their DEC 861C power controllers into?
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Be carefull doing this. All foreign 240 mains that I have worked with have
been 240 between hot and neutral. This works out to be 416 phase to phase
on 3 phase systems. What you will be doing is 240 between 2 hots. This
can and will cause problems with a lot of supplies that expect the neutral
to be at / near ground. I have several isolation transformers that I use
for all the UK equipment I service and they all are wired for 240 Hot to
neutral output.
Also be careful what electrician you get to set it up for you. I have seen
plenty of them manage to wire them wrong. I have even had to explain to
them how to wire a buck / boost transformer only to have them fuse it for
isolation ratings.
>Here's how I'm avoiding this problem for my collection: I'm moving into a
>new house and getting 220 installed where my stuff it going to be
>located.. since it's right where the breaker panel is, it's not going to
>cost much at all... so if the computer in question is going to be located
>in a basement or wherever the breaker panel is, you don't even need a
>transformer... just get an electrician, friend, or do it yourself..
>
>Kevin
>
> First, to get common names:
> Hot = one Phase
> Neutral = Protective Ground
> Ground = Ground (the starpoint on 3 phases connected to earth at the
'generator')
> Hot and Ground are the basic wires to tap power,
Wrong... HOT and NEUTRAL provide the power legs. Earth Ground is only for
protection and does not carry any power.
The power company generates three phase because it is more efficient.
However, in most residential areas they only provide a single phase. It
doesn't make economic sense for them to string three wires when a single
phase will suffice.
The single phase (high voltage) is fed into a simple center tapped
transformer where it provides 240 VAC for high power appliances and
2-phases each with 120 VAC for lighting and general use.
|| <---------- 120 VAC (HOT)
----------> || <
> || <
HV > || <---------- Neutral
> || <
----------> || <
|| <---------- 120 VAC (HOT)
In the early days, it was common for manufactures to use the device chassis
or frame as a conductor. They would tie the Neutral wire to the chassis
(under the assumption that the potential was near 0V) and save a few
pennies in the manufacturing process. The problem was, it was possible to
put the plug in the socket upside-down. This meant the chassis was tied to
the hot leg and you could get electrocution just touching the device. In
the 50's and 60's it was quite possible to get shocked by your TV by just
turning it on!
Today, most devices have polarized plugs so that can't happen.
The neutral line should NEVER be fused. If that fuse happened to blow and
the one on the HOT(s) leg didn't, the device would still be hot (even with
a blown fuse). This would cause an unsafe condition.
Steve Robertson - <steverob(a)hotoffice.com>
>Tony wrote:
>> No. The US mains is 234V centre-tapped. It's not part of a 3-phase system
>> (at least not normally)
>
>Except in the sense that the incoming "single phase" power is derived
>from two out of three phases somewhere higher up in the distribution
>hierarchy. The utility company doesn't generate different "single phase"
>power for residential customers.
It is taken from 1 hot (13 to 14KV) of the 3 phase grid.
Dan
>Tim,
>
>I should have qualified that as common residential and business circuits.
>Sure it's possible to go to 60A, how many houses nomially have that?
>(don't include mine).
>
>Allison
>
I have a few 50A 120 and 240v. Then to I have a 400A house service that I
subfed 200A to my office / shop and then to the shed where the welder is.
I even put a 100A panel on the wall behind the row of 7 6 foot racks for the
test beds. It was cheaper and easier than putting all those Hubbell's on
the wall.
Dan
To help reduce the US power confusion I just hand scratched a US single
phase power configuration from the pole transformer into the first breaker
panel. All panels after the first one are not allowed to have the Neutral
and Ground tied together. (Sub feed panels)
Please ignore the horrible hand drawing I just want people to be safe.
ftp://zane.brouhaha.com/pub/dan/power.gif
Dan
OK, so it's not the holy grail (apple lisa) , but it's close. Picked up a
complete Hero1 with speech synth and arm in his own custom carrying box. it
came complete with charger, cables, all schematics and manuals and some dos
based compiler programs to write apps that can be downloaded to the robot via
serial link. Also got a data book on all motorola chips and some robotics
study courses as well as lots of handwritten notes by the original owner.
Unfortunately, he doesnt work right. I think his motor drive may have to be
rebuilt and although he did say "okay" once, his digital display is scrambled
and he wont initialise. Gel cell batteries will have to be replaced since
he's been sitting for at least 5 years. Will be a fun project and will get
plenty of space on the upcoming computer museum website.
I'm no expert on Roman numerals, but I recently saw a movie released in MCMXLIX. Now, we know what the MCM means, but I submit that the intention of chiseling as little stone as possible, the romans avoided the use of 4 successive numerals by use of bi-quinary counting. However, the use of IX for 9 as opposed to VIV, as in the MCM above, is a bit ambigous. I'm not planning any trips to the former Roman Empire, so I doubt I'll do better than trusting the conclusion reached in this forum. Does anybody have an authoritative reference?
Dick
-----Original Message-----
From: Hans Franke <Hans.Franke(a)mch20.sbs.de>
To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu>
Date: Tuesday, April 20, 1999 3:10 PM
Subject: Re: Program Challenge (was Re: z80 timing... 6502 timing)
>
>> > > Convert a binary value to Roman, using ASCII characters (or
>> > > the native character set if applicable) into a string
>> > > with a termination character (if ASCII, use the NUL (0)
>> > > character).
>> > Is a length terminated record valid ?
>
>> Hmmmm ... I might be inclinded to say yes, but is there any reason it
>> can't be NUL terminated (or terminated with the appropriate termination
>> character for the character set)?
>
>Just since it is the usual way within the OS I'm trying to code.
>NUL is like any other caracter valid within a string. Also, it
>gieve me an disadvantage - instead of just adding '\0' I have
>to calculate the string.
>
>> > > The valid Roman characters used are IVXLCDM
>> > Is Space valid ? Romans did include them at will.
>> I did not know that, but for this program no, spaces are not allowed.
>
>Ok.
>
>> > > > There are a few details which have been left out of the specification for
>> > > > this task.
>> > > > Does it require input validation?
>> > > I think I specified that. The valid range of Roman numerals is 1 through
>> > > 3,999 inclusive. The routine does have to check that and construct a
>> > > special string ( "*" ) if the input is not in that range.
>> > > > Is the binary input pure binary, or is it BCD?
>> > > Okay, that might be a valid point, but it's pure binary, not BCD.
>
>> > Fine, you stated max input 3999, but to be checked, and you
>> > stated binary, but in what format ? Half Word (16 Bit),
>> > Word (32) or Double Word (64) ?
>
>> Uh, I was unaware that halfwords had a specific size (on the DEC Alpha, a
>> half word would be 32 bits in size).
>
>Like Words, they are just machine dependant ... in a given 32 Bit CPU
>a halfword is just 16 - so whats the input ? (in fact, I'll assume 32 Bit)
>
>> > To be transfered at a given location, or via a pointer,
>> > or via register (attention, might again be processor specific).
>
>> Appropriate to the CPU or the situation. Obviously, a 6502 can't pass it
>> in a single register, but there are other options. That's why I didn't
>> specify how to pass the data in.
>
>:))) And why specifying a '\0' byte ?
>
>> > > I liked Sam's suggestion of ``printing to memory'' as a way to avoid the
>> > > complications of I/O in this, and if I didn't make this clear that the
>> > > conversion was to be stored in memory, I'm sorry.
>>
>> > Output, to a given location (pointer) or static buffer ?
>> > Check for buffer length or asumption of an buffer, always big
>> > enough ? (if you check the binary number you also have to check
>> > the buffer (if given).)
>
>> Again, it's up to the programmer. But be prepared to justify your answers
>> 8-)
>
>:))
>
>> -spc (Welcome to the world of programming 8-)
>
>All simple, all the same, isn't it ?
>
>And again, more questions:
>If I'm right at Megans description, she just include the next lower
>digit when it comes to these subtraction rules, and your Algo seams
>to be weak at the same point. Let me give an example:
>
>49 would be normaly coded as IL (always remember, it was kind of a
>system to reduce writing as much as possible - there are even examples
>where the number 248 is written CIIL) while Megan seams to code it as
>XXXXIX - basicly wrong - or did I miss something ? I'm not realy
>what one can call a DEC-Geek.
>
>So do we only have to supporte the one-less rule, or the rule
>of one subtraction numeral - or the full possibility with the
>goal to reduce writing to a max ?
>
>Gruss
>H.
>
>Oh, BTW: this contest is exacty into the direction where we didn't
>want to go - we are comparing algorythms and not CPUs - for a more
>CPU dependant contest we need to fix the algo to use, so the difference
>will reflect the differences in processor design and not into algo
>design (of course there's more sex appeal in the my-algo-is-bether-
>than-yours, than in the my-(what-ever-algo)-implementation-is-better).
>
>So I still go for the idea of implementing one algo as good as possible
>for the different CPUs - more on Friday (I'm not full time available
>until then).
>
>
>
>--
>Stimm gegen SPAM: http://www.politik-digital.de/spam/de/
>Vote against SPAM: http://www.politik-digital.de/spam/en/
>Votez contre le SPAM: http://www.politik-digital.de/spam/fr/
>Ich denke, also bin ich, also gut
>HRK
<Perhaps soft iron #2 washers would be a better choice. The local hardware
Same material as the nuts. A higer carbon steel (more remnant magnetizem)
may work but you really want small to keep the drive resonable.
Allison
