Graphs of current vs voltage (or power) for incadescent bulb

[Tim Shoppa]

Does anyone know if there exists, preferably on the web, a set of
graphs that show current vs voltage (or resistance vs RMS power or
any other equivalent) for common low-voltage bulbs?

I'm specifically looking for bulbs which may serve as a decent
AC current regulator. (Think "ballast tube" if you're old enough).
I've done some experiments with bulbs I had
laying around and they seem pretty good in the glow-dull-red region.

If anyone has any good rules-of-thumb (e.g. "run at 0.5 the rated
voltage and it'll pass sqrt(0.5) the rated current") I'll gladly
consider them
too as starting points. Above sample rule-of-thumb was chosen out
of think air and while it works for some bulbs it doesn't really help
me find points which will be good for constant current operation.

Worst case, I buy one of each kind of bulb from Mouser and make the
tests myself . But I'd prefer to find manufacturer's curves
on the web. I already checked Chicago Miniature and they didn't have
anything obvious.

Tim.

 

[Tim Shoppa]

I wrote:
Ian replied:

There are devices built for this that are much
better than bulbs, comprising a thermistor
inside a vacuum capsule.

Real ballast tubes are iron wires inside a hydrogen-filled bulb.
Somehow the hydrogen provides cooling that lets them deliver very
constant current. But they are hard to come by these days.

It seems that some small incadescent bulbs are vacuum-filled (is that
an oxymoron?) and others are argon filled. Maybe the argon-filled ones
will have better constant-current performance. But I don't know how to
tell the difference just by looking.

My requirements are not all that stiff: ten or twenty percent variation
in (nominal) 300mA current over, say, 6 to 18V drop would be fine. I
thought that a properly chosen bulb (or maybe a series string or maybe
a parallel group) may do this for me. If you can name a
maker/distributor of these thermistor/vacuum capsule devices, and if
they're cheap (less than a few bucks each), I am interested.

Tim.

 

[Tim Shoppa]

Why not an LM317 and a resistor?

A LM317 does not handle AC voltage all that well .

The need is for AC (sine wave) in, AC (sine wave) out. Converting to
DC in the middle is possible, but I'm looking for something cheap and
simplistic (thus light bulbs)! Some semi-sloppy current regulation is
all I desire, and rectifying, smoothing, chopping, and filtering to get
funked up current-regulated AC out is way too complicated.

Tim.

 

[Tim Shoppa]

I've used CdS photo cells (resistive) controlled
by an incandescent bulb tweaked by a comparator.

And I've used this idea with great success in Wein bridge oscillators.

But in my latest need, the power dissipation is 300mA x 14V or around 4
or 5 watts. A CdS photocell isn't good for anywhere near that much
power.

Tim.

 

[Robert]

"Luhan Monat" <x@y.z> wrote in message newsI4pe.3238$7s.2494@fed1read01...

Luhan Monat wrote:

Tim Shoppa wrote:

Why not an LM317 and a resistor?



A LM317 does not handle AC voltage all that well .

The need is for AC (sine wave) in, AC (sine wave) out. Converting to
DC in the middle is possible, but I'm looking for something cheap and
simplistic (thus light bulbs)! Some semi-sloppy current regulation is
all I desire, and rectifying, smoothing, chopping, and filtering to get
funked up current-regulated AC out is way too complicated.

Tim.


Hewlett Packard used a #49 lamp for there variable sine wave generator.
To get an idea for a specific bulb: measure the 'cold' resistance with an
ohmmeter; calculate the 'hot' resistance by dividing the power by the
current squared. Most lamp have about a 10:1 ratio.

I find them very useful in design of protection circuits.


OOooops. P=(E^2)/R; so R=p/(E^2).

--
Luhan Monat: luhanis(at)yahoo(dot)com

You were right the first time.

P = I^2*R so => R = P/I^2

If you want to stay with voltage then you need to rearrange what you gave.

It's P = E^2/R so => R = E^2/P not the version you mentioned.

Robert

 

[JeffM]

You can click on the original post to see the original equations,
but this takes time and extra steps
since you have to back out of that page
and hope your browser puts you at the same point on the original page.
Mike Monett

If you hold down the Ctrl key when you click on a link,

it will open in another window (leaving your original window intact).

You can configure Mozilla's browsers to open a new tab
instead of a new window.

There is also a link at the top-right of every thread page
for Fixed Font (monospaced).
..
..

"Math Notation via Email"
http://www.karlscalculus.org/email.html

"Math Notation with ASCII"
http://mathforum.org/typesetting/ascii.examples.html

"Guidelines for Using ASCII"
http://mathforum.org/typesetting/ascii.guidelines.html

"Order of Operations"
http://mathforum.org/dr.math/faq/faq.order.operations.html

"Typing Math"
http://mathforum.org/dr.math/faq/faq.typing.math.html

Nice collection.

 

[JeffM]

Here's your post in html.
...you can't predict where your post will end up on the page
http://groups.google.ca/group/sci.electronics.design/msg/dd1ee660e5c3f8aa?hl=en
Mike Monett

Mike, Tony,
you still have the "show options/show original" buttons
that'll give you the true ascii text.
Fred Bartoli

In this case, the Fixed Font link right there on the page

works just fine.
http://groups.google.ca/group/sci.electronics.design/msg/dd1ee660e5c3f8aa?&fwc=1

BTW, all: "hl=en" means "English-only".
You can delete it from any Google link
and let the preferences of the person who clicks the link take over.

In the archive of s.e.d., it has no meaning at all.

 

[JeffM]

query string parameters
Rich Grise

Say it loud!

..
..

http://www.google.com/search?q=%22escaped+quote%22
is different from
http://www.google.com/search?q=escaped+quote .
(or _should_ be.)

Always has been. Until recently, however,

http://www.google.com/search?q="escaped+quote"
and
http://www.google.com/search?q=escaped-quote
were the same.

A few months ago, Google changed the algorithm and
http://www.google.com/search?q=escaped-*-quote
will get you escaped quote or escaped convict quote

and
http://www.google.com/search?q="escaped+*+quote"
will return escaped convict quote
but does not return escaped quote .
..
..

if you need a quoted string, just stick a %22 or so in there -
that's an "escaped" quote mark.

If you're posting links,

inserting %22 is the least preferable method WRT the Usenet Archive.
Google will accept
http://www.google.com/search?q="escaped+quote"
as a URL and deal with it.

If all who post a URL with a leading %22,
added a leading + like this %22+escaped+quote%22
it would make their strings Google-searchable
(without changing the viability of the link)
so that folks searching the Archive
would not have to run their search strings once (regular)
then tack 22 onto the front of them and try again

BUT THIS "escaped+quote"
makes it FIVE CHARACTERS SHORTER and only takes 1 search.
..
..
..
Hex characters
%20 whitespace Replace it with a + if using double quote
marks
%22 Replace it with " (double quotes)
%26 & (Don't try to replace it; use the ASCII code.)
%27 Replace it with ' (apostrophe)
%2B Replace it with . (period)
%3A Replace it with : (colon)
%40 Replace it with @ (at sign) Anybody ever heard another
name for this?

GENERAL GOOGLE STUFF (You covered most of this.)
&q= query (search string)
&hl=en language (English)
&safe=off don't filter results for what might be offensive in Utah
&filter=0 show every page that matches (sub-threads, Supplemental
Results, etc.)
&ie= input encoding (character set) e.g., UTF-8
Shift_JIS (Japanese)
&oe= output encoding (character set) ISO-8859-1
ISO-2022-JP
&num= maximum number of items per page
&lr= Not sure--someone said it is limit (maximum number of
items)
&btnL= I saw where someone said it means "I'm feeling lucky"--but
that can't be.
&btnG= By his logic, this means "Google" search (links; search
string shown in context)
&c2coff= ??
&dq= ??

IN LINKS TO GOOGLE'S CACHED PAGES
&strip=1 show the cached page without the graphics

GOOGLE GROUPS
&scoring=d sort by date (Google Groups)
&selm= old syntax individual message (un-threaded post)

FROOGLE
&scoring=p sort by price
..
..
Anybody got more?

 

[Watson A.Name - \"Watt Su]

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:1118083891.149400.88160@g44g2000cwa.googlegroups.com...

Why not an LM317 and a resistor?

A LM317 does not handle AC voltage all that well .

The need is for AC (sine wave) in, AC (sine wave) out. Converting to
DC in the middle is possible, but I'm looking for something cheap and
simplistic (thus light bulbs)! Some semi-sloppy current regulation is
all I desire, and rectifying, smoothing, chopping, and filtering to
get
funked up current-regulated AC out is way too complicated.

Tim.

Try this. Put the LM317 as the load across the + and - of a bridge
rectifier. Connect the ~ leads to the AC. I'm not sure you need a cap
across it in this app. You still have to worry about compliance, etc.

 

Watson A.Name - "Watt Sun, the Dark Remover" wrote:

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:1118075404.491085.212570@g14g2000cwa.googlegroups.com...
Does anyone know if there exists, preferably on the web, a set of
graphs that show current vs voltage (or resistance vs RMS power or
any other equivalent) for common low-voltage bulbs?

I'm specifically looking for bulbs which may serve as a decent
AC current regulator. (Think "ballast tube" if you're old enough).
I've done some experiments with bulbs I had
laying around and they seem pretty good in the glow-dull-red region.

If anyone has any good rules-of-thumb (e.g. "run at 0.5 the rated
voltage and it'll pass sqrt(0.5) the rated current") I'll gladly
consider them
too as starting points. Above sample rule-of-thumb was chosen out
of think air and while it works for some bulbs it doesn't really help
me find points which will be good for constant current operation.

Worst case, I buy one of each kind of bulb from Mouser and make the
tests myself . But I'd prefer to find manufacturer's curves
on the web. I already checked Chicago Miniature and they didn't have
anything obvious.

Tim.

I got some 1869(?) 28V, 40mA lamps from Rat Shaft and used them for the
neg Rf of a Wein Bridge osc. They came 2 to a pkg and both of them were
intermittent. I got another pkg and they were also intermittent.
Apparently when you apply full V they work okay, but the tungsten
filament is clamped in the support wire mechanically, the support is
just bent over and squoze on to it. At low temps, the connection can be
loose, but at high temps at full brightness the thermal expansion keeps
it in good contact. So don't be surprised if such phenomena manifest
themselves in your measurements.

I simply can't resist commenting on this.

The Wien-bridge circuit is named after German Professor Max Wien
(1866 - 1938), whose name is not spelled Wein. (Wien, pronounced
"veen", is how the city of Vienna is called in German, whereas
Wein, pronounced "vain", means wine.)

Consult <http://home.att.net/~theremin1/200/wien.html> for more
information on Max Wien.

Did your "intermittent" bulbs show this effect only when used in the
Wien-bridge oscillator? Then your oscillator may have suffered from
"squegging", a common problem when these circuits are run at higher
frequencies and at low lamp power.

Best regards,

Martin.

 

clicliclic@freenet.de schrieb:

Watson A.Name - "Watt Sun, the Dark Remover" wrote:
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:1118075404.491085.212570@g14g2000cwa.googlegroups.com...
Does anyone know if there exists, preferably on the web, a set of
graphs that show current vs voltage (or resistance vs RMS power or
any other equivalent) for common low-voltage bulbs?

I'm specifically looking for bulbs which may serve as a decent
AC current regulator. (Think "ballast tube" if you're old enough).
I've done some experiments with bulbs I had
laying around and they seem pretty good in the glow-dull-red region.

If anyone has any good rules-of-thumb (e.g. "run at 0.5 the rated
voltage and it'll pass sqrt(0.5) the rated current") I'll gladly
consider them
too as starting points. Above sample rule-of-thumb was chosen out
of think air and while it works for some bulbs it doesn't really help
me find points which will be good for constant current operation.

Worst case, I buy one of each kind of bulb from Mouser and make the
tests myself . But I'd prefer to find manufacturer's curves
on the web. I already checked Chicago Miniature and they didn't have
anything obvious.

Tim.

I got some 1869(?) 28V, 40mA lamps from Rat Shaft and used them for the
neg Rf of a Wein Bridge osc. They came 2 to a pkg and both of them were
intermittent. I got another pkg and they were also intermittent.
Apparently when you apply full V they work okay, but the tungsten
filament is clamped in the support wire mechanically, the support is
just bent over and squoze on to it. At low temps, the connection can be
loose, but at high temps at full brightness the thermal expansion keeps
it in good contact. So don't be surprised if such phenomena manifest
themselves in your measurements.


I simply can't resist commenting on this.

The Wien-bridge circuit is named after German Professor Max Wien
(1866 - 1938), whose name is not spelled Wein. (Wien, pronounced
"veen", is how the city of Vienna is called in German, whereas
Wein, pronounced "vain", means wine.)

A much better match is: Wein, pronounced "vine", means wine. Sorry.

Consult <http://home.att.net/~theremin1/200/wien.html> for more
information on Max Wien.

Did your "intermittent" bulbs show this effect only when used in the
Wien-bridge oscillator? Then your oscillator may have suffered from
"squegging", a common problem when these circuits are run at higher
frequencies and at low lamp power.

Best regards,

Martin