Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
--
These are my opinions, not necessarily my employer's. I hate spam.
On Mon, Jul 20, 2009 at 11:59:46PM -0700, Hal Murray wrote:
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
I'm not sure, but some ideas come to mind:
28V is a common supply voltage for some RF transistors, particularly
amplifiers.
28VDC is also common on aircraft -- including their battery strings.
That, or it's related the Phone Company (tm) -- while their strings
are at 48V, the buses are typically floated on rectifiers at 54-56V which
you could divide to around 28V easily.
Alternatively, maybe it's just easy to regulate down to 24, or
+/- 12V, accounting for voltage drop across the regulators.
--msa
2009/7/21 Hal Murray hmurray@megapathdsl.net:
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
A nominal 24V lead-acid battery on charge will have a terminal voltage
of 27.6V (I believe) so perhaps this is where it comes from.
73,
Steve
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
--
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--
Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
A man with one clock knows what time it is;
A man with two clocks is never quite sure.
----- Original Message -----
From: "Hal Murray" hmurray@megapathdsl.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, July 21, 2009 2:59 AM
Subject: [time-nuts] Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
Hal,
Where did you find that Isotemp OSCO 127-10 data sheet ?
Any other data on that unit?
Phil
In the early days of radios, there were A and B batteries. A were 2,
4 or 6 volt. B were 90 to 120 volts
in glass accumulators.
These were taken back to the radio shop to be recharged when flat.
This is where the 6.3 volt filament voltage for vacuum tubes came from,
the voltage of a 3 cell accumulator on discharge, the A battery.
When radios were to be used with motor generator sets, particularly
the military,
the standard was for 7 volts, the voltage on a 3 cell accumulator on
charge , and there as even a
series of 7 volt filament valves for military use.
As more power was required, particularly to power genemotors, battery
banks were
doubled and doubled to give 14 volts and then 28 volts. At this
stage with genemotors
any voltage could be made to order, and voltage was regulated with
carbon pile series regulators
at the 28 volt level. A genemotor with 28 volt input could produce
-150 V for bias and 250V
and 600V for seriously powered radio transmitters.
Aircraft also came into the picture, also with generator supported
accumulators.
Car radios used vibrators and transformers to transform 12v to 260
volts.
It was not until 1960 onwards that solid state power supplies began
to appear.
The telephone industry used higher voltages around 50 I think, from
accumulators
under charge.
So that is where these standard voltages came from.
Cheers, Neville Michie
On 21/07/2009, at 5:17 PM, phil wrote:
----- Original Message ----- From: "Hal Murray"
hmurray@megapathdsl.net
To: "Discussion of precise time and frequency measurement" <time-
nuts@febo.com>
Sent: Tuesday, July 21, 2009 2:59 AM
Subject: [time-nuts] Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks,
they come
conviently packaged in 6V and 12V units. The phone company works
off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or
21-30V
which straddles both 24V and 28V.
Hal,
Where did you find that Isotemp OSCO 127-10 data sheet ?
Any other data on that unit?
Phil
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time-nuts
and follow the instructions there.
Hal
I think you will find that 28 volts DC is standard in many aviation and
military mobile equipment power requirements. It is the nominal battery
voltage that comes from two 12 volt cells in series that are fully charged.
The voltage to run such equipment is not critical (can be less than 28
volts), as you normally charge two series 12 volt cells at 27.6 volts - this
is indicative of the nominal voltage of such supplies. Trust that this is
the information you are looking for ?
Roy Phillips.
----- Original Message -----
From: "Hal Murray" hmurray@megapathdsl.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, July 21, 2009 7:59 AM
Subject: [time-nuts] Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
--
These are my opinions, not necessarily my employer's. I hate spam.
time-nuts mailing list -- time-nuts@febo.com
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
28V is a nominal voltage, not an exact voltage. It is derived from the
system voltage of a 24V battery that is being continuously charged.
The typical lead acid battery, as used in vehicles, wants to be charged at
a voltage that will quickly return it to full charge after the high starting
load has been removed. That requires about 2.3V per cell, which leads to
28V nominal. Your car works this way too, and if you measure the voltage
on your battery while the car is running, you will find your 12V is really
13.8 to 14.5V
-Chuck Harris
Hal Murray wrote:
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
Most wireless sites will be 28 volts also. Some are switching to the telco standard of -48 which when measured is actually around -56 volts. One reason for going to a higher voltage is, you can use smaller conductors to get same amount of power out.
Not to steal the thread, but any one know why the telephone company choose to use a negative voltage? Where as the positive is referenced to ground? When I was a kid I was told it was because they discovered that the battery terminal would corrode if it was done that way?
Corrosion protection, similar to why the old MG cars ran on a positive
ground.
On Tue, Jul 21, 2009 at 8:25 AM, n3izn@aol.com wrote:
Most wireless sites will be 28 volts also. Some are switching to the telco
standard of -48 which when measured is actually around -56 volts. One reason
for going to a higher voltage is, you can use smaller conductors to get same
amount of power out.
Not to steal the thread, but any one know why the telephone company choose
to use a negative voltage? Where as the positive is referenced to ground?
When I was a kid I was told it was because they discovered that the battery
terminal would corrode if it was done that way?
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n3izn@aol.com Wrote:
Not to steal the thread, but any one know why the telephone company choose to use a negative
voltage? Where as the positive is referenced to ground? When I was a kid I was told it was
because they discovered that the battery terminal would corrode if it was done that way?
Negative 48 was chosen for several reasons, but the primary reason a negative potential was chosen was due to negative voltages causing less galvanic corrosion to outside plant; splices and copper wires outside corrode more quickly when at a positive potential relative to ground.
--
Lamar Owen
Chief Information Officer
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC 28772
828-862-5554
www.pari.edu
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The higher voltage is used to get a longer range for the subscriber loop
in the pre amplifier days w/o using heavier wire. Remember, there is LOT
of copper in a POTS netrork.
They probably studied the problem very thoroughly in the late 1800s,
trading off cost for safety (electrocution danger). There was no PVC or
Teflon, just wax and dry paper.
I seem to remember the positive ground was for corrosion protection.
-John
=============
Most wireless sites will be 28 volts also. Some are switching to the telco
standard of -48 which when measured is actually around -56 volts. One
reason for going to a higher voltage is, you can use smaller conductors to
get same amount of power out.
Not to steal the thread, but any one know why the telephone company choose
to use a negative voltage? Where as the positive is referenced to ground?
When I was a kid I was told it was because they discovered that the
battery terminal would corrode if it was done that way?
time-nuts mailing list -- time-nuts@febo.com
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At 10:25 AM 7/21/2009, n3izn@aol.com wrote...
Not to steal the thread, but any one know why the telephone company
choose to use a negative voltage? Where as the positive is referenced
to ground? When I was a kid I was told it was because they discovered
that the battery terminal would corrode if it was done that way?
Using negative voltages on the lines (referenced to ground) reduces
corrosion, by making the conductor cathodic.
Hi Hal:
Automotive electrical systems are said to be "12 Volts" (or "24 Volts" for
military vehicles). That's the voltage of a six cell lead acid battery when
it's discharged. It's fairly common to run down a car battery by say using a
ham radio while the car is parked. The rated voltage of a rechargeable battery
is the discharged value.
But the same electrical system when installed in an aircraft is called a "14
Volt" system ("28 Volts" for military aircraft). In aircraft the engine is
always running and the generator is always charging the battery. You don't
park an airplane in the sky.
The 12/14 volt system can see a range of 10 to 15 Volts and the 24/28 volt
system will see a range of 20 to 30 Volts.
Have Fun,
Brooke Clarke
http://www.prc68.com
Hal Murray wrote:
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
abcde
----- Original Message -----
From: "Roy Phillips" phill.r1@btinternet.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, July 21, 2009 12:04 PM
Subject: Re: [time-nuts] Where does 28V come from?
Hal
I think you will find that 28 volts DC is standard in many aviation and
military mobile equipment power requirements. It is the nominal battery
voltage that comes from two 12 volt cells in series that are fully
charged. The voltage to run such equipment is not critical (can be less
than 28 volts), as you normally charge two series 12 volt cells at 27.6
volts - this is indicative of the nominal voltage of such supplies. Trust
that this is the information you are looking for ?
Roy Phillips.
----- Original Message -----
From: "Hal Murray" hmurray@megapathdsl.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, July 21, 2009 7:59 AM
Subject: [time-nuts] Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off
48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
--
These are my opinions, not necessarily my employer's. I hate spam.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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and follow the instructions there.
Phone companies work off a standard 48v (often referred to as 50v) for exchanges and 'in building' installations. This includes mobile phone operators. But a significant amount of equipment in the mobile network is not in the exchange sites - it is in the BTS (Base Transmitter System) cabinets, where 28v is used. Henace a lot of ex-mobile phone co equipment, such the HP/Symmetricom Z380xx, Lucent RFTG's that were around, and power amplifiers used on 23 and 13cm amateur bands, is normally capable of being powered from either 28V or 48V supplies, since it could be deployed in either situation.
73,
Dave, G4HUP
From: Roy Phillips phill.r1@btinternet.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Tuesday, 21 July, 2009 4:42:01 PM
Subject: Re: [time-nuts] Where does 28V come from?
abcde
----- Original Message ----- From: "Roy Phillips" phill.r1@btinternet.com
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Tuesday, July 21, 2009 12:04 PM
Subject: Re: [time-nuts] Where does 28V come from?
Hal
I think you will find that 28 volts DC is standard in many aviation and military mobile equipment power requirements. It is the nominal battery voltage that comes from two 12 volt cells in series that are fully charged. The voltage to run such equipment is not critical (can be less than 28 volts), as you normally charge two series 12 volt cells at 27.6 volts - this is indicative of the nominal voltage of such supplies. Trust that this is the information you are looking for ?
Roy Phillips.
----- Original Message ----- From: "Hal Murray" hmurray@megapathdsl.net
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Tuesday, July 21, 2009 7:59 AM
Subject: [time-nuts] Where does 28V come from?
That said, the modules also appear to be powered by 28VDC, add some
regulation, you could use the chassis to power the Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For cars/trucks, they come
conviently packaged in 6V and 12V units. The phone company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
which straddles both 24V and 28V.
-- These are my opinions, not necessarily my employer's. I hate spam.
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Others have said it all, but see MIL-STD-704F < http://assist.daps.dla.mil/docimages/A/0000/0003/5901/000000433000_000000038767_BDJDANQSPS.PDF?CFID=32790482&CFTOKEN=123a955522c88712-9E5138E6-1372-548A-D3D5BB2597F5676D&jsessionid=0630a8f7f91d568172ed > or < http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=35901 > for specifications and MIL-HDBK-845 < http://assist.daps.dla.mil/docimages/A/0000/0011/0257/000000482523_000000172526_MROJWPALXS.PDF?CFID=32789554&CFTOKEN=578349968949c304-9E4997F9-1372-548A-D384056DE208ED29&jsessionid=0630a8f7f91d568172ed > or http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=110257 > for more info.
28V needs half the current for the same power. This results in lighter wires, switches etc. The newest standard for cars (Automobiles) is 42V bus with 36V (3x12V) battery standard, they are jumping 28/24V completely.
Robert G8RPI.
--- On Tue, 21/7/09, Hal Murray hmurray@megapathdsl.net wrote:
From: Hal Murray hmurray@megapathdsl.net
Subject: [time-nuts] Where does 28V come from?
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Date: Tuesday, 21 July, 2009, 7:59 AM
That said, the modules also appear
to be powered by 28VDC, add some
regulation, you could use the chassis to power the
Thunderbolt, and
mount it in one of the blank panels.
Lead acid batteries are close to 2V per cell. For
cars/trucks, they come
conviently packaged in 6V and 12V units. The phone
company works off 48V.
But where does 28V come from?
The Isotemp OSCO 127-10 data sheet says 27 V, but that's
+3, -6 or 21-30V
which straddles both 24V and 28V.
--
These are my opinions, not necessarily my employer's.
I hate spam.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
In message 768062.16062.qm@web27101.mail.ukl.yahoo.com, Robert Atkinson write
s:
The newest standard for cars (Automobiles) is 42V bus with
36V (3x12V) battery standard, they are jumping 28/24V completely.
That one has run into all sorts of trouble.
It was sort of predicated on people with microwave ovens and
dishwashers in their hummers and that entire market has more or
less evaporated.
42V was chosen over 56V because the latter is "high voltage" according
to various countries codes.
Poul-Henning
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Poul-Henning Kamp
Sent: Tuesday, July 21, 2009 10:45 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Where does 28V come from?
In message 768062.16062.qm@web27101.mail.ukl.yahoo.com, Robert Atkinson write
s:
The newest standard for cars (Automobiles) is 42V bus with
36V (3x12V) battery standard, they are jumping 28/24V completely.
That one has run into all sorts of trouble.
It was sort of predicated on people with microwave ovens and
dishwashers in their hummers and that entire market has more or
less evaporated.
42V was chosen over 56V because the latter is "high voltage" according
to various countries codes.
Higher voltages are being driven by a couple factors, independent of dishwasher installation..
There is a desire to reduce the wiring harness mass and cost. Higher voltages let you use smaller wires, so you spend less money on copper and insulation.
For things like electric motor driven power steering and airconditioning, higher voltages are better (smaller wires, lower mass, better efficiency) and would allow doing away with hydraulic pumps and belt driven compressors. Wires are a lot easier to move around than belts and pulleys, so that makes internal layout easier for the styling folks.
There is a also a desire to do point of load switching (which also reduces mass.. fewer wires). Historically, there was a problem getting semiconductor switches with appropriate parameters to do high side switching. A Vds-on of 1 Volt is awfully big in the context of a 12V device (that might actually be running at 9V during cranking). It's less of a problem in the context of a 50V bus.
Working against this is that semiconductors sort of start at about 60V ratings. A 42 volt bus (still being a multiple of 6, for historical reasons.. darn those Babylonians) gives you 18V margin against the 60V. (especially if you consider that 14.4V is the actual max voltage for a 12V system... 42=50.4V)
And then there's the 50V threshold for "low voltage systems" that Poul mentions.
I think the latter is starting to be less important, as more hybrid cars have high voltage battery packs show up in the field and we haven't seen dozens of firefighters electrocuted by inadvertently cutting the wires, or shop technicians dying by putting a screwdriver where they shouldn't.
You're still stuck in the cost trade between higher voltage semiconductors and lower copper and actuator costs with higher voltages, and even more, between the cost of things like transient suppression.
I'll note that spacecraft have been going to higher voltage buses for this kind of reason (except for science spacecraft, which tend to stick with the venerable 28V avionics power, since it's familiar, and there tends to be a lot of scrounging of surplus and reuse of proven designs). ISS uses, I think, 100V DC as the bus, and commercial comsats use bus voltages of 70-90V.
In message <ECE7A93BD093E1439C20020FBE87C47FEB749828B8@ALTPHYEMBEVSP20.RES.AD.J
PL>, "Lux, James P (337C)" writes:
Higher voltages are being driven by a couple factors, independent
of dishwasher installation..
There is a desire to reduce the wiring harness mass and cost.
Higher voltages let you use smaller wires, so you spend less money
on copper and insulation.
True, but the car industrys plan was the that dishwasher-in-hummer
segment was going to pay the development costs, making "42V electrical"
a "high-end-feature", thus making people desire it in lower grade
cars, rather than having to actually stuff it down peoples throats.
Right now, 42V car are "D.E.A.D" according to my sources in the
autoindustry, partly, as you point out, in light of the hybrid/electric
market expected to explode, but mostly, because nobody has the money
to develop and push the new standard.
Poul-Henning
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Dave,
dave powis wrote:
Phone companies work off a standard 48v (often referred to as 50v) for exchanges and 'in building' installations. This includes mobile phone operators. But a significant amount of equipment in the mobile network is not in the exchange sites - it is in the BTS (Base Transmitter System) cabinets, where 28v is used. Henace a lot of ex-mobile phone co equipment, such the HP/Symmetricom Z380xx, Lucent RFTG's that were around, and power amplifiers used on 23 and 13cm amateur bands, is normally capable of being powered from either 28V or 48V supplies, since it could be deployed in either situation.
In all environments I encounter it, it is called 48V and not 50V. There
also exists a -60 VDC standard. For Europe, it is standardized as ETSI
EN 300 132-2. For US Bellcore (now Telecordia) wrote it into it's NEBS
series, but I can't recall the number from the top of my head.
The ETSI variant is online, so fetch that.
The ETSI people have created another interesting spec, the EN 300 132-3
which is for a 400 VDC system. It avoids the step of DC-AC conversion in
UPS systems since most supplies rectifies it anyway. Check it out. :)
Cheers,
Magnus