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Graphs of current vs voltage (or power) for incadescent bulbs?

T

Tim Shoppa

Jan 1, 1970
0
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

Ian Stirling

Jan 1, 1970
0
In sci.electronics.design Tim Shoppa said:
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.

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

John Larkin

Jan 1, 1970
0
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 have a citation of

amps = K * volts^0.541.

which you could check against a few cases.


John
 
T

Tim Shoppa

Jan 1, 1970
0
I said:
[AC current regulator]

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.
 
J

John Larkin

Jan 1, 1970
0
I said:
[AC current regulator]

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.

Why not an LM317 and a resistor?

John
 
T

Tim Shoppa

Jan 1, 1970
0
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.
 
P

Phil Hobbs

Jan 1, 1970
0
John said:
I said:
[AC current regulator]

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.


Why not an LM317 and a resistor?

John

Across a bridge rectifier.

Cheers,

Phil Hobbs
 
J

Jim Thompson

Jan 1, 1970
0
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.

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

...Jim Thompson
 
J

John Fields

Jan 1, 1970
0
I said:
[AC current regulator] <-----------------------------------------------+
|
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. |
|
|
Why not an LM317 and a resistor? ------------------------------------------+
 
J

John Larkin

Jan 1, 1970
0
John said:
I wrote:

[AC current regulator]

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.


Why not an LM317 and a resistor?

John

Across a bridge rectifier.

Or back-to-back, with schottkies?

PTC thermistor?


John
 
D

Don Klipstein

Jan 1, 1970
0
I said:
[AC current regulator]

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.

Why not an LM317 and a resistor?

The LM317 does make a nice current regulator.

But should Tim Shoppa have some requirement or desire to use a lamp
(wants the regulator to glow?) then I would parallel a bunch of 25 watt
A19 "standard" or "soft white" incandescents. (I doubt these particular
ones glow much below 18 volts because of greater filament cooling by the
gas, although higher and lower wattages and tubular "refrigerator"
/"showcase" lamps up to 40 watts [vacuum] do.)

Incandescents usually have a vacuum if very low wattage and/or low
current - less than roughly 25 watts per inch of visibly apparent
length-plus-diameter of filament. Incandescents of higher power/current
than this tend to be gas filled. Lower current incandescents have a
vacuum instead of a gas because the heat conduction losses by the gas
outweigh the benefits of gas slowing down filament evaporation and
permitting a higher filament temperature. This is because a narrower
filament has a higher temperature gradient in the gas around the filament,
which largely cancels out the lower filament surface area.
Incandescents of design that barely has a net benefit by the gas have
greatest effect of the gas - current varying less with voltage, and light
output and life varying more with voltage than is the case with other
incandescents. And these differences in performance variation with
voltage are greater at low voltage - especially near or a little below the
threshold of visibly producing light - than they are near design voltage.

I once many years ago plotted current as a function of voltage for a
gas filled flashlight lamp (HPR52), and found the curve to be almost
flat in some range of low voltages - I believe about .3-.8 volt.

- Don Klipstein ([email protected])
 
F

Fred Bartoli

Jan 1, 1970
0
Tim Shoppa said:
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.

So put the 317 inside a rectifier bridge (if the discontinuity isn't too
sloppy).
 
T

Tim Shoppa

Jan 1, 1970
0
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.
 
In sci.electronics.design Tim Shoppa said:
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.

I have a Wagner Lighting automotive lamp catalog that has a table with
some of this information, but it's general data, not specific to each
lamp number.

I once heard that there are empirical formulas for this involving odd
things like thirteenth and ninth powers, but I don't recall exactly
what they are.

I have taken the liberty of cross-posting (and setting followups)
to sci.engr.lighting, which should yield much better info.

Matt Roberds
 
S

Spehro Pefhany

Jan 1, 1970
0
I said:
[AC current regulator]

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.

Eg. the old Amperite devices. Last I saw them they were going for
upwards of $100 a pop.
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.

Here's an old graph of current vs. voltage for line voltage Xmas tree
type bulbs:

http://www.speff.com/bulb.gif


Best regards,
Spehro Pefhany
 
G

Guy Macon

Jan 1, 1970
0
Tim said:
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.

Any such set of curves would also have to account for time.
At a constant voltage, the resistance/current changes as the
bulb warms up.
 
J

John Perry

Jan 1, 1970
0
Fred said:
So put the 317 inside a rectifier bridge (if the discontinuity isn't too
sloppy).
....And if it is too high, could you use it in series with a 14V power
transformer?

John Perry
 
T

truegridtz

Jan 1, 1970
0
Tim Shoppa said:
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 am not to sure exactly what they do, B&K tube testers use a pair of bulbs
to regulate something. I recall that they are number 55. B&K says they
must be replaced as a pair from the same manufacturer.

They have something to do with the meter. If one of them burns out the
meter goes crazy. Thought this might give you a clue. Good Luck, Mark
 
L

Luhan Monat

Jan 1, 1970
0
Tim said:
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.
 
L

Luhan Monat

Jan 1, 1970
0
Luhan said:
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).
 
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