Looking to power a mini halogen bulb to do film capture. It would be great
if I could power it off the movie projector itself without having to get an
additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a
factor. Does that mean that the voltage needs to be higher than the bulb
rating or not necessarily?

What I wonder is if this 24v bulb should work off the 24v socket on the
projector?

http://www.1000bulbs.com/product.php?product=685

Thanks

HiC wrote:

Looking to power a mini halogen bulb to do film capture. It would be great
if I could power it off the movie projector itself without having to get an
additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a
factor. Does that mean that the voltage needs to be higher than the bulb
rating or not necessarily?

What I wonder is if this 24v bulb should work off the 24v socket on the
projector?

I'd be more concerned about overloading the transformer in the projector
myself.

Graham

On Sun, 15 Oct 2006 08:37:01 GMT, "HiC" wrote:

Looking to power a mini halogen bulb to do film capture. It would be great
if I could power it off the movie projector itself without having to get an
additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a
factor. Does that mean that the voltage needs to be higher than the bulb
rating or not necessarily?

The actual no load voltage will almost always be higher than the
under-load voltage - unless the power supply is regulated (most movie
projectors aren't regulated unless you have a theater projector)

Voltage ratings on incandescent bulbs have to be taken with some
skepticism. They are usually intended to be "nominal" ratings.

For instance, a 12 Volt bulb intended for auto use will spend most of
its life working at 13.8 or higher and the people that make the bulbs
know that and take it into account.

Likewise projectors. The 21 volt bulb may be intended to run at 21
volts or 24 volts - unless you see the manufacturers curves regarding
ambient temperature, color temperature of the light, voltage and life
expectancy you're just "whistling in the dark."

Sometimes a lower voltage bulb is used at a higher voltage - it
shortens the life, but puts out more light and puts out higher color
temperature light - so color renditioning may be better.

Likewise, under load, your 24 volts will almost certainly be lower
than 24V.

What I wonder is if this 24v bulb should work off the 24v socket on the
projector?

http://www.1000bulbs.com/product.php?product=685

Thanks

Get a 24 V lamp and try it. If you can't live with the color (should
be "warmer" -less blue) be happy and expect the lamp to last longer
than a 21 V lamp in the same application .



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On Sun, 15 Oct 2006 12:22:14 +0100, Eeyore
wrote:



HiC wrote:

Looking to power a mini halogen bulb to do film capture. It would be great
if I could power it off the movie projector itself without having to get an
additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a
factor. Does that mean that the voltage needs to be higher than the bulb
rating or not necessarily?

What I wonder is if this 24v bulb should work off the 24v socket on the
projector?

I'd be more concerned about overloading the transformer in the projector
myself.

Graham

He seems to be implying that the 24 volts is measured output and 21
volts is the proper bulb for the projector - so the voltage under load
is expected to be lower. In that case using a 24 volt lamp to replace
a 21 volt one will be less strain on the transformer.

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default wrote:
On Sun, 15 Oct 2006 08:37:01 GMT, "HiC" wrote:

Looking to power a mini halogen bulb to do film capture. It would be great
if I could power it off the movie projector itself without having to get an
additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a
factor. Does that mean that the voltage needs to be higher than the bulb
rating or not necessarily?

The actual no load voltage will almost always be higher than the
under-load voltage - unless the power supply is regulated (most movie
projectors aren't regulated unless you have a theater projector)

Voltage ratings on incandescent bulbs have to be taken with some
skepticism. They are usually intended to be "nominal" ratings.

For instance, a 12 Volt bulb intended for auto use will spend most of
its life working at 13.8 or higher and the people that make the bulbs
know that and take it into account.

Likewise projectors. The 21 volt bulb may be intended to run at 21
volts or 24 volts - unless you see the manufacturers curves regarding
ambient temperature, color temperature of the light, voltage and life
expectancy you're just "whistling in the dark."

Sometimes a lower voltage bulb is used at a higher voltage - it
shortens the life, but puts out more light and puts out higher color
temperature light - so color renditioning may be better.

Likewise, under load, your 24 volts will almost certainly be lower
than 24V.

What I wonder is if this 24v bulb should work off the 24v socket on the
projector?

http://www.1000bulbs.com/product.php?product=685

Thanks

Get a 24 V lamp and try it. If you can't live with the color (should
be "warmer" -less blue) be happy and expect the lamp to last longer
than a 21 V lamp in the same application .

A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v
reading is under load or not. If its with no load, OP needs a 21v bulb,
anything else will just be crap. Depending on the type of psu, it may
be possible to change the output voltage to suit other bulbs
voltage-wise. Whether they will have the right optical situatoin is
another matter.


NT

wrote:

A 24v bulb is likely to be a 28-29v bulb in reality

So how come you can buy 28V bulbs too ?

Graham

On Sun, 15 Oct 2006 16:27:06 +0100, in sci.electronics.design Eeyore
wrote:



wrote:

A 24v bulb is likely to be a 28-29v bulb in reality

So how come you can buy 28V bulbs too ?

Graham

Thats for when you have a 35V supply :-)


martin

On 15 Oct 2006 07:43:59 -0700, wrote:

A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v
reading is under load or not. If its with no load, OP needs a 21v bulb,
anything else will just be crap. Depending on the type of psu, it may
be possible to change the output voltage to suit other bulbs
voltage-wise. Whether they will have the right optical situatoin is
another matter.


NT

Then one is "second guessing" the lamp specifications, the
manufacturer specifications, and the ops application.

To make a really good "informed judgment" one would have to know how
the manufacturer originally intended the lamp to work - perhaps they
were sacrificing some life to add better color rendition.

Anyhow the op may be transferring film to video or digital.

He states: "Looking to power a mini halogen bulb to do film capture."

That could easily mean transferring film to digital (or tape). If it
is done via computer he could just as easily adjust the white level /
color temp, as fiddle with the hardware.

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You are supposed to underpower the light bulb. Why do you think normal
house light bulbs are 120v when you only have 110v at the outlet. It
increases the life of the light bulb.

On Oct 15, 9:35 am, martin griffith
wrote:
On Sun, 15 Oct 2006 16:27:06 +0100, in sci.electronics.design Eeyore

wrote:

wrote:

A 24v bulb is likely to be a 28-29v bulb in reality

So how come you can buy 28V bulbs too ?

GrahamThats for when you have a 35V supply :-)

martin

default wrote:
On 15 Oct 2006 07:43:59 -0700, wrote:

A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v
reading is under load or not. If its with no load, OP needs a 21v bulb,
anything else will just be crap. Depending on the type of psu, it may
be possible to change the output voltage to suit other bulbs
voltage-wise. Whether they will have the right optical situatoin is
another matter.


NT

Then one is "second guessing" the lamp specifications, the
manufacturer specifications, and the ops application.

Not really. The vast majority of 24v bulbs are for road use, where
nominally 24v systems are IRL approx 28-29v. The lamps are designed to
run on those systems.

I suppose the OP could underpower the bulb as you say, but its not the
best option. It should work, but 21v on a 28v bulb will give lousy
results.


NT

spake thus:

On Oct 15, 9:35 am, martin griffith
wrote:

On Sun, 15 Oct 2006 16:27:06 +0100, in sci.electronics.design Eeyore

wrote:

wrote:

A 24v bulb is likely to be a 28-29v bulb in reality

So how come you can buy 28V bulbs too ?

Thats for when you have a 35V supply :-)

You are supposed to underpower the light bulb. Why do you think normal
house light bulbs are 120v when you only have 110v at the outlet. It
increases the life of the light bulb.

Not really true: all of those various designations--110 volts, 117
volts, 120 volts--are just that, *nominal* designations for standard
line voltage, which can vary but is somewhere in the range 110-120
volts. It's not as if light bulb manufacturers rate their bulbs for a
higher voltage than that actually used.

By the way, for those who don't know, it's true that light bulbs run at
less than their "rated" voltage will last longer--in some cases, a *lot*
longer--than if used at normal voltage (for instance, there's an
original Edison bulb somewhere which is still burning). But there's a
downside: when you run a bulb this way, you get more heat than light,
and they become even more inefficient. (Their light is also a lot more
reddish.)


--
"In 1964 Barry Goldwater declared: 'Elect me president, and I
will bomb the cities of Vietnam, defoliate the jungles, herd the
population into concentration camps and turn the country into a
wasteland.' But Lyndon Johnson said: 'No! No! No! Don't you dare do
that. Let ME do it.'"

- Characterization (paraphrased) of the 1964 Goldwater/Johnson
presidential race by Professor Irwin Corey, "The World's Foremost
Authority."

"default" wrote in message
...

Anyhow the op may be transferring film to video or digital.

He states: "Looking to power a mini halogen bulb to do film capture."

That could easily mean transferring film to digital (or tape). If it
is done via computer he could just as easily adjust the white level /
color temp, as fiddle with the hardware.

Actually there's a specific reason to use a lower wattage mini-bulb. I need
a less powerful lamp to project a useable image through a diffuser and
condenser lens and bounce it into the camera with a front surface mirror.
Normal projector lamps are too bright.

wrote:
You are supposed to underpower the light bulb. Why do you think normal
house light bulbs are 120v when you only have 110v at the outlet. It
increases the life of the light bulb.



That's news to me, it was 110V back in the 1950s but has been 120V
nominal for quite some time. I just measured mine and it's 121.4V at the
moment.

If you undervolt an incandescent bulb the light output drops far more
rapidly than the wattage and for a given amount of light you end up
spending dollars more on electricity to extend the life of a 25 cent bulb.

"Meat Plow" wrote in message
news
What's the projector capable of delivering in full load watts ?

Don't know, I just turned it to "lamp" and put the multi tester leads on it,
came up with about 24.2 V. I know the bulbs it uses are rated at 150 w.

Actually, that's another thing, how do I know if I can use a much lower
wattage lamp without doing damage? Is there some way to tell? Any markings
on the electronics of the projector I should look for?

"HiC" wrote in message
ink.net...

Actually, that's another thing, how do I know if I can use a much lower
wattage lamp without doing damage? Is there some way to tell? Any markings
on the electronics of the projector I should look for?

Pretty much OK as long as the wattage is say 10% or more of original.

On Mon, 16 Oct 2006 00:23:52 GMT, "HiC" wrote:


"Meat Plow" wrote in message
news
What's the projector capable of delivering in full load watts ?

Don't know, I just turned it to "lamp" and put the multi tester leads on it,
came up with about 24.2 V. I know the bulbs it uses are rated at 150 w.

Actually, that's another thing, how do I know if I can use a much lower
wattage lamp without doing damage? Is there some way to tell? Any markings
on the electronics of the projector I should look for?

If you are going from 150 watts to 10 watts . . . that is much less
strain on the transformer and you'd want a 24 volt lamp as opposed to
a 21 volt one - the voltage drop due to loading will be less

As a general rule, you can always use less current/power safely - It
is when you go higher that things tend to smoke.



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On 15 Oct 2006 15:45:18 -0700, wrote:

default wrote:
On 15 Oct 2006 07:43:59 -0700, wrote:

A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v
reading is under load or not. If its with no load, OP needs a 21v bulb,
anything else will just be crap. Depending on the type of psu, it may
be possible to change the output voltage to suit other bulbs
voltage-wise. Whether they will have the right optical situatoin is
another matter.


NT

Then one is "second guessing" the lamp specifications, the
manufacturer specifications, and the ops application.

Not really. The vast majority of 24v bulbs are for road use, where
nominally 24v systems are IRL approx 28-29v. The lamps are designed to
run on those systems.

I suppose the OP could underpower the bulb as you say, but its not the
best option. It should work, but 21v on a 28v bulb will give lousy
results.



Here in the states, most cars use 12 volts. I've seen some indication
that 42 volts may be in the offing in future cars. There are still a
few 6 volt systems around in vehicles.

We do have some 24 VAC equipment; it is a popular "control" voltage
for relays, valves, HVAC control circuits, etc.. and some lighting . .
.. like "landscape","accent" and pathway lights.

He's talking about reducing the power used dramatically - so he will
have close to 24 volts under load - assuming I'm following all this
correctly.


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default wrote:
On Mon, 16 Oct 2006 00:23:52 GMT, "HiC" wrote:


"Meat Plow" wrote in message
news

What's the projector capable of delivering in full load watts ?

Don't know, I just turned it to "lamp" and put the multi tester leads on it,
came up with about 24.2 V. I know the bulbs it uses are rated at 150 w.

Actually, that's another thing, how do I know if I can use a much lower
wattage lamp without doing damage? Is there some way to tell? Any markings
on the electronics of the projector I should look for?


If you are going from 150 watts to 10 watts . . . that is much less
strain on the transformer and you'd want a 24 volt lamp as opposed to
a 21 volt one - the voltage drop due to loading will be less

As a general rule, you can always use less current/power safely - It
is when you go higher that things tend to smoke.



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A 10 watt lamp is not going to like the much higher
transfomer output, any transformer, not loaded with
150 watts will output quite some more than 24 volts.
(if the loaded voltage at 150W is 24.2)

wrote:

You are supposed to underpower the light bulb. Why do you think normal
house light bulbs are 120v when you only have 110v at the outlet. It
increases the life of the light bulb.


It screws up the color temperature of the lamp, and if the voltage is
low enough on a halogen bulb, it causes problems with the tungsten being
deposited on the glass, rather than back on the filament. I ran a B&W
film chain at a TV station back in the '70s. The bulbs were rated at 20
hours when run at 120 volts. I couldn't get two dozen new bulbs a
month, so I ran them at 90 volts, and got a minimum of 300 hours out of
each lamp. I had to increase the gain on the camera to compensate, and
the picture was quite red. If I went any lower than 90 volts the video
was so grainy I couldn't use it. This was on a pair of RCA TP-66
projectors.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"Sjouke Burry" wrote in message
. ..

A 10 watt lamp is not going to like the much higher
transfomer output, any transformer, not loaded with
150 watts will output quite some more than 24 volts.
(if the loaded voltage at 150W is 24.2)

It's a a 20 watt bulb I'm looking to power. Might go higher if I don't find
the light bright enough. Don't know if that makes a difference.

HiC wrote:
"Sjouke Burry" wrote in message
. ..

A 10 watt lamp is not going to like the much higher
transfomer output, any transformer, not loaded with
150 watts will output quite some more than 24 volts.
(if the loaded voltage at 150W is 24.2)

It's a a 20 watt bulb I'm looking to power. Might go higher if I don't find
the light bright enough. Don't know if that makes a difference.

20w 24v bulb should be fine. Ditto 35 or 50w 24v.


NT

default wrote:

Here in the states, most cars use 12 volts. I've seen some indication
that 42 volts may be in the offing in future cars. There are still a
few 6 volt systems around in vehicles.

We do have some 24 VAC equipment; it is a popular "control" voltage
for relays, valves, HVAC control circuits, etc.. and some lighting . .
. like "landscape","accent" and pathway lights.

He's talking about reducing the power used dramatically - so he will
have close to 24 volts under load - assuming I'm following all this
correctly.

No cars run on 12v, theyre 13-15v systems called 12v for historical
reasons. 24v nominal or 28-29v real is standard voltage for truck
electrical systems, which is what nearly all 24v bulbs are for, hence
theyre really 28v bulbs.

I thought 24v was the off load supply voltage... but I accept its not
100% clear.


NT

HiC wrote:

Actually there's a specific reason to use a lower wattage mini-bulb. I need
a less powerful lamp to project a useable image through a diffuser and
condenser lens and bounce it into the camera with a front surface mirror.
Normal projector lamps are too bright.

How about a neutral grey filter?

I was origianlly going to write a warning about testing the new bulb
arrangement before using it on unreplaceable film, to check for melting
or scorching of the film. However, if you are going to a lower power
bulb, and it survives, you shouldn't have that problem.

Another worry: Are you planning to stop the film at each frame to
capture the image? If so, beware of overheating the film. In normal
use, each frame of the film spends a short time stopped for
projection(1/24 second, is that right?) and is only illuminated for a
portion of that time.

"Richard Henry" wrote in message
ups.com...

How about a neutral grey filter?

I was origianlly going to write a warning about testing the new bulb
arrangement before using it on unreplaceable film, to check for melting
or scorching of the film. However, if you are going to a lower power
bulb, and it survives, you shouldn't have that problem.

Another worry: Are you planning to stop the film at each frame to
capture the image? If so, beware of overheating the film. In normal
use, each frame of the film spends a short time stopped for
projection(1/24 second, is that right?) and is only illuminated for a
portion of that time.

Some projectors dropped in a metal shield with small holes punched in it for
still frame projection.

Homer J Simpson spake thus:

"Richard Henry" wrote in message
ups.com...

Another worry: Are you planning to stop the film at each frame to
capture the image? If so, beware of overheating the film. In normal
use, each frame of the film spends a short time stopped for
projection(1/24 second, is that right?) and is only illuminated for a
portion of that time.

Some projectors dropped in a metal shield with small holes punched in it for
still frame projection.

My old Hell & Bowel Filmosound has a neat little fail-safe "trap door"
shield like that; a little perforated aluminum screen that's blown aloft
by the fan so it's normally out of the way. If the fan ever fails for
some reason, the screen drops into the light path.


--
"In 1964 Barry Goldwater declared: 'Elect me president, and I
will bomb the cities of Vietnam, defoliate the jungles, herd the
population into concentration camps and turn the country into a
wasteland.' But Lyndon Johnson said: 'No! No! No! Don't you dare do
that. Let ME do it.'"

- Characterization (paraphrased) of the 1964 Goldwater/Johnson
presidential race by Professor Irwin Corey, "The World's Foremost
Authority."

default wrote:
On 15 Oct 2006 15:45:18 -0700, wrote:


default wrote:

On 15 Oct 2006 07:43:59 -0700, wrote:

A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v
reading is under load or not. If its with no load, OP needs a 21v bulb,
anything else will just be crap. Depending on the type of psu, it may
be possible to change the output voltage to suit other bulbs
voltage-wise. Whether they will have the right optical situatoin is
another matter.


NT

Then one is "second guessing" the lamp specifications, the
manufacturer specifications, and the ops application.

Not really. The vast majority of 24v bulbs are for road use, where
nominally 24v systems are IRL approx 28-29v. The lamps are designed to
run on those systems.



Aircraft use 28V but I've never seen a 24V car, they're all 12V aside
from very old 6V cars.

"James Sweet" wrote in message
news:f0YYg.4599$5v5.2097@trndny08...

Aircraft use 28V but I've never seen a 24V car, they're all 12V aside from
very old 6V cars.

IIRC many trucks use 24 volts.

http://www.cb-shack.com/shop/index.php?cPath=81