Driver to drive?

[Guy Macon]

Jim Thompson wrote:

I understand there's also a "tester" which forces shunts to close when
they didn't when the bulb failed. Anyone know about where to obtain
and how well it works? (I have a 12' pre-wired tree with one section
out.)

High voltage across the entire string, current limited so that when
the shunt closes it doesn't supply enough current to burn out the
bulbs.

 

[Guy Macon]

Thaas wrote:

Guy wrote:

Whichever part of the system is negative loses metal and
whichever part of the system is positive gains metal.

Okay, now you've got my head spinning. Which is it? Does material
leach from the more positive conductor and deposit on the more
negative, or is it the other way round?

AAARGH!!! I wrote it BACKWARDS! Do'h! Whichever part of the
system is negative gains metal and whichever part of the system
is positive losess metal.

Profuse apologies!

 

[Arie de Muynck]

"Arie de Muynck" ...

Ever tried to start a halogen bulb on a constant voltage / constant
current
source where the current limit is just above the normal operating current?

I did.
It doesn't.

That was of course one with a current foldback, not constant current or it
would have worked. I did change the supply to constant current.
Typically R_cold = 0.1 R_hot

Arie.

 

[Don Pearce]

On Tue, 07 Dec 2004 15:01:11 -0500, Mike Monett <no@spam.com> wrote:

Here's a puzzle. If anyone can solve it, you guys can.

Astronomy Picture of the Day (APOD) has an unusual picture taken just
after a gray streak apparently hit a streetlamp, causing a flash and
some smoke. Investigation showed damage to the housing and the lamp had
failed. Photos taken before and after the flash do not show the gray
streak. The more you study it, the stranger it becomes. Here's the url:

http://antwrp.gsfc.nasa.gov/apod/ap041207.html

Best Wishes,

Mike Monett

Not very convincing. The streak is constant density all the way across
- looks digitally added to me.

d

Pearce Consulting
http://www.pearce.uk.com

 

[Mike Monett]

Guy Macon wrote:

Carl Ijames wrote:

If positive ground is so great for anticorrosion, why did the US auto
industry eventually standardize on negative ground? Are there
disadvantages?

Neither kind of ground is "anticorrosion." Whichever part of the
system is negative loses metal and whichever part of the system
is positive gains metal. With telephone systems, ground stakes
are a lot easier to replace than wires are. With automotive
systems, body and frame parts are harder to replace than wires are.
Also, there was a time when cars had vacuum tube (valve) radios,
which are happier with a negative ground. Finally, it is easier
to explain a system if you can say "the current comes out of the
positive battery terminal, goes through the light bulb, and returns
to the negative battery terminal." (It really doesn't, as we all
know, but it's too late to correct Ben Franklin's bad guess.)

--
Guy Macon
http://www.guymacon.com/

Nice description, Guy. Just a short note on convention current flow.

IIRC, Michael Faraday established the direction of conventional current
flow while he was working on electrolysis. At that time, nobody knew
about electrons, or atoms, or ions. Faraday noticed the positive
electrode got smaller and the negative electrode increased. Obviously,
something had to be leaving the positive electrode and moving to the
negative one.

Of course, he had no way of knowing electrons cannot flow in an
electrolyte, and ions were the charge carriers in the solution.
This was entirely understandable and forgiveable, given the lack of
knowledge at the time.

Also, here's another clue showing Faraday's genius. Batteries of the
time did not hold constant voltage, which messed up his calculations on
mass transfer.

To overcome this problem, he put his cells in series, so each one would
have exactly the same current. Then everything worked out as ratios.

Without our Fluke DVM's and Tek scopes, how many of us could figure this
out?

Another advantage of being first is you get some constant named after
you. And so now we have the Faraday constant, which is used anywhere you
have electrolysis, as in aluminum refining, electroplating, and
corrosion.

Best Wishes,

Mike Monett

 

[John Woodgate]

I read in sci.electronics.design that Guy Macon <_see.web.page_@_www.guy
macon.com_> wrote (in <10rbq9rtb9g8f7a@corp.supernews.com&gt about
'What's in self shunting Xmas light bulbs?', on Tue, 7 Dec 2004:

If you want to do advanced research, measure the voltage and
current in circuit while the string is operating; the resistance of the
filament gets lower when it is hot.

That'll be the day.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Nicholas O. Lindan]

"Carl D. Smith" <cdsmith69NOSPAM@earthlink.net> wrote

Later, another bulb or two went out right when I was looking at
the tree. Then a few seconds later several more went, and the
remaining bulbs got much brighter. But that didn't last long.
Just as I was thinking it was time to go unplug the tree, the
remaining bulbs went off like old fashioned camera flash bulbs in
a series of flashes.

Great product design: If the customer is too cheap to buy a box of
replacement bulbs he gets to buy a whole new string ...

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

[John Bäckstrand]

Not very convincing. The streak is constant density all the way across
- looks digitally added to me.

NASA prankster? Not likely, imho. There are literally tons of possible
_natural_ explanations for this one. The small flash looks alot like
something produced in the lens, but the streak I have no good
explanation for. An insect flying by the camera would likely explain
this though, someone on slashdot said the EXIF says flash was fired
(why? No idea), so the flash combined with a insect zooming by would
explain it, however the streak is much too straight to really look like
the path of a flying insect. The flash could probably kill small insects
that are too close to it, Ive scarred plastic stuff by holding them
infront of the flash, on the other hand the flas seems to be fired in
the lowest position.

There are lots of other possible causes: blowing bulb, shadow from a
jetstreak (both?) or a actually, why not a meteor?

---
John Bäckstrand

 

[Guy Macon]

John Woodgate wrote:

If you want to do advanced research, measure the voltage and
current in circuit while the string is operating; the resistance of the
filament gets lower when it is hot.

That'll be the day.

Note to self: next time, smoke the crack *after* posting...

Seriously, I had trouble sleeping last night so I got up and
read a few newsgroups, and I manages to get several things
exactly backwards. D'oh! The resistance of the filament
gets higher when it is hot. The current through the filament
gets lower when it is hot.

I blame Bush for any errors I may have made.

 

[Moskvich]

engr wrote:

I tried asking this question in sci.electronics.equipment,
but didn't get any responses from owners/users of the
scopes listed below. Please don't post that I should
buy two more used 465's on EBAY. Please post your opinions
on these NEW scopes listed below (if you've used one).

-----
I've got a worn out 465B. I know there are a lot
of used Tek scopes for sale on EBAY, but I feel
like I'd just be buying more problems. So I'd
like to get a new scope.

The reason for choosing an analog scope is to
keep the cost down to less than $2000 (US).

I've looked at Tek's cheap line of digital
scopes, and they have noise all over the traces.
They even show it in their literature.
I can't really justify the $4000 for their
good digital scopes, the TDS30xx series.

So my question is, can anyone recommend a good
(new) analog scope ? Here are some choices:

LeCroy LA302 ($1895 US)
http://www.lecroy.com/tm/products/analog/LA302-303/LA302-303.asp

Hitachi VI-1560 or VI-1565 ($1695 US)
http://www.calibration.com/sale/new/hitachi/vc1585.html

Kenwood CS-5405 ($1595 US)
http://www.tequipment.net/KenwoodCS5405.html

Leader LS-8105A ($1495 US)
http://www.tequipment.net/LeaderLS8105A.html


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----

Hi
You can easily compare various oscilloscopes at
the test and measurement equipment buyers guide site
http://www.testbuyer.com
Regards

 

[Jonathan Kirwan]

On Tue, 07 Dec 2004 15:59:52 -0700, Jim Thompson <thegreatone@example.com>
wrote:

The dirty part (see a semiconductor
physics book) is that Is is a HORRIBLE transcendental function of
temperature.

Yes, included in my post (which I posted before reading this branch.)

Jon

 

[Moskvich]

Hello,
Try to find best oscilloscope at
http://www.testbuyer.com
Regards

 

[Moskvich]

Hello,
Try to find best oscilloscope at
http://www.testbuyer.com
Regards

 

[Martin Riddle]

Looks like a knat flew in front of the lens.

"Mike Monett" <no@spam.com> wrote in message news:41B60C07.1F02@spam.com...

Here's a puzzle. If anyone can solve it, you guys can.

Astronomy Picture of the Day (APOD) has an unusual picture taken just
after a gray streak apparently hit a streetlamp, causing a flash and
some smoke. Investigation showed damage to the housing and the lamp had
failed. Photos taken before and after the flash do not show the gray
streak. The more you study it, the stranger it becomes. Here's the url:

http://antwrp.gsfc.nasa.gov/apod/ap041207.html

Best Wishes,

Mike Monett

 

Jim Thompson wrote:

gm = Ie*q/(kT)

or

re = kT/q/Ie

No Is to be seen ;-)

They should actually call
this the Shockley emitter TRANS-resistance,
instead of just resistance.
After all, we are just inverting the
transconductance.


Slick

 

[Yzordderrex]

Ok, thanks Ken. I'll play around some more. It is acting a little
contrary to what I would expect in that a step up in voltage causes it
to reduce the output. I expect if I zoom in I'll see the FB signal
overshoot, which is then causing the dip. Prof only wants the thing
to run a 60Hz sinewave, so homework done.

regards,
Bob

 

[Yzordderrex]

Ok, thanks Ken. I'll play around some more. It is acting a little
contrary to what I would expect in that a step up in voltage causes it
to reduce the output. I expect if I zoom in I'll see the FB signal
overshoot, which is then causing the dip. Prof only wants the thing
to run a 60Hz sinewave, so homework done.

regards,
Bob

 

[legg]

On Mon, 06 Dec 2004 05:20:27 -0500, Mike Monett <no@spam.com> wrote:

And you can let them know how much you like the new interface here:

http://groups-beta.google.com/support

Requires re-registration using an interface incompatible with some
older browsers.

The tree and dates were the few features that made the original format
attractive. It used to have trouble though, as I recall keeping them
straight, due to its own delays in posting. Now the delay is
reportedly gone, but the features are dropped anyways.

This is called over-compensation.

If they sever the previously symbiotic relationship with usenet, then
they become just another bunch of Yahoos. I wonder could usenet take
the hit? This thread does not show a signifigant number of google
postings, already.


Welcome to Google Beta. Let me take your hat........


RL

 

[Ross Herbert]

On Mon, 29 Nov 2004 19:40:31 +0100, "Arie de Muynck"
<send.spam.to@spammer.org> wrote:

At least in Europe, most telephone exchanges use a negative voltage
referenced to good old mother Earth.

Why negative? Is it some 'cathodic protection' in case a pinhole leak
occurred?

The main reason for having "positive earth" is to prevent corrosion
and oxidation. this article explains the reason reasonably although
there is rather more to it;

http://engr.smu.edu/~levine/ee8302/positiveground.pdf

In the 1946 book, The Telephone Handbook 8th edition by Joseph Poole
AMIEE Wh. Sc. and later revised by N.V Knight B.Sc., AMIEE and W.
Prickett, page 203 states;

"The positive terminal of the main battery is earthed at all exchanges
so as to obtain uniformity in signalling over junctions, with earth
and battery connections. With negative potential on the line
conductors, earth faults are not masked by chemical deposits on the
conductors, forming insulating films at the point of contact with the
earthed object, as would be the case with positive polarity, and such
faults are therefore rapidly brought to light."

Since oxidisation is a form of mild electrolytic action and this
process makes itself evident at the anode or positive terminal, it
means that exchange connection points such as relay and switch
contacts etc which are positive with repect to ground, would become
oxidised thus creating insulating deposits which would result in major
problems for maintenance. Since both moisture and chemical impurities
are present in the atmosphere which is in contact with the metal
contact points and wiring joints (particularly underground cables),
the opportunity for oxidisation to occur in a large network becomes
enormous considering the number of such points which exist.

The reference to uniformity of signalling is not really a reason why
positive earthing is used since it refers simply to a standard method
for conveying the signals required for setting up and clearing
connections, and this function would be necessary irrespective of
which polarity was utilised. It perhaps refers to the fact that since
other telephone engineering companies also used positive earthing that
it would be wise to follow the same course for the sake of uniformity
of signalling. One has to remember that this was in the days prior to
automatic telephone exchanges where manual CB working was the norm and
human operators carried out the connection and supervisory processes
using dc line signalling in the main.

Some present day organisations have published information that the
positive earthing system was started by telco's in the 1940's but this
is plainly false and misleading. Positive earthing was around long
before the 1940's.
http://www.xantrex.com/web/id/340/docserve.asp
http://www.epanorama.net/links/telephone.html

 

[Mike Monett]

Frithiof Andreas Jensen wrote:

"Mike Monett" <no@spam.com> wrote in message news:41B4326B.2388@spam.com..

And you can let them know how much you like the new interface here:

Why.do.I.care.?

Frithiof,

Your point about the original programmers cashing out is probably
true.

Here's part of a post by Robert Monsen in the original format. You
can see the header showing his email address, the date, and the
subject. The page breaks are as he entered them, and the ascii
schematic is quite readable. The link is http://tinyurl.com/5ro7f

--------------------------------------------------------------------
From: Robert Monsen (rcsurname@comcast.net)
Subject: Re: using a 5v relay with 12v
Newsgroups: sci.electronics.basics, sci.electronics.design
Date: 2004-12-05 12:25:29 PST

Matt wrote:

Yes, the relay is rated at 5v to turn on, and 250v for whatever it is
running. I have 12v to the coil now, it is getting a bit hot. I'm not sure
if they are supposed to get hot since they are such low resistance.

Can you tell me more about the power saving trick? Do I put a low value
resister in series w/ the coil and put a cap in parallel with this resister?
what value do you suggest?

BTW - are there any simple RC circuits to delay the turn on of the relay for
a couple seconds?

Thanks!
-matt

It takes a particular voltage, usually something like 80% of the nominal
coil voltage, to close a relay. However, it takes much less than that to
keep it closed. You can take advantage of this by using an arrangement
whereby turning it on generates a larger voltage.
7V
+------+
| |
|< .-.
CTRL ---| | | 4.7k
|\ | |
| '-'
| |
o------|--------------------o-----\
| | | 12V
| | - Relay
.-. | || ^ Coil
10k| | o-----------||-------o-----/
| | | || |
'-' | V
| |/ C -
'----| |
|> |
| |
'--------------------'
GND

(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
--------------------------------------------------------------------

Here's the same post in the new format. The link is
http://tinyurl.com/667gb

The same link that previously pointed to the individual post now
points to the entire thread, and previous references to individual
links are now broken.

You have to scroll down to find the desired message, and it may be
difficult to describe which one if the same person made several
entries. This is essential in some of the larger threads with
hundreds of posts, but apparently there is no way to do this.

The text that Robert quoted is not shown. You have to click on 'show
quoted text' to see it, and the link does not work in older
browsers. So you may be unable to see what he is responding to.

The schematic now has ascii character 160 instead of spaces. Your
browser may display this character normally, but none of the
browsers I use can do so. This makes the schematic unreadable.

--------------------------------------------------------------------
Robert Monsen
Dec 5, 12:25 pm show options

Matt

- Show quoted text -

It takes a particular voltage, usually something like 80% of the nominal
coil voltage, to close a relay. However, it takes much less than that to
keep it closed. You can take advantage of this by using an arrangement
whereby turning it on generates a larger voltage.

7V
          +------+
| |
|< .-.
CTRL ---|       | | 4.7k
        |\      | |
| '-'
| |
          o------|--------------------o-----\
| | | 12V
| | - Relay
         .-.     |           ||       ^    Coil
      10k| |     o-----------||-------o-----/
         | |     |           ||       |
'-' | V
| |/ C -
          '----|                      |
|> |
| |
                 '--------------------'
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
--------------------------------------------------------------------

If the schematic were part of the original post, it would appear at
the top of the thread where lines are automatically broken to fit in
the narrow column. Then, it would not make any difference which
browser you use. The schematic would be unreadable.

The same problem exists in the software newsgroups. Often, a poster
will include a section of code he wants to discuss with the original
message. With the new format, the code would be turned into
meaningless gibberish.

You can look at the tree and try to find the message, but still have
the problem identifying it in long threads. The result is you may
waste a great deal of time finding a desired post, and when you do,
it may be unreadable.

These changes make google groups unusable for many people.

Best Wishes,

Mike Monett