[Andre Jute[_2_]]

I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

[Patrick Turner]

On Mar 4, 5:06*am, Andre Jute wrote:
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

I cannot assume the Vac is 230V and VAC could be less if there is a
transformer for a lower voltage applied to the lamp, and perhaps you
have a rectifier and Vdc applied.
But the same series R should work.

Once you know voltage and current across the globe, its R = V/I, and
to substitute the globe resistance you will need something rated for
180W.
This is not too difficult if you purchase adequate power resistors
from RS and hook them up on a remote heatsink or dangle the lot in a
bucket of oil.
Otherwise you could simply use a number of incandescent 230Vac
tungsten lamp globes in parallel, maybe 15W + 60W + 100W and with
trimming resistance all to mimic the original globe.

Low voltage lamp globes for auto use, 12V, can be seriesed if they are
all exactly the same watt rating.

I have often used light globes for dummy loads for a tube amp supply;
with a 500V supply a couple of series 60W lamps mimics 2 x KT88, and I
don't need an expensive lot of resistors which have to be large and be
kept at much lower temperatures than small amounts of muct hotter
tungsten.

But nornal incandescent laps are now banned from sale in Oz
supermarkets and all lamps sold are compact fluorescents which have
SMPS and are completely unsuitable for temporary resistors. But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used. The dimmers chop
parts out of the sine wave to effectively turn off the sine wave for
part of each cycle, and without any heat dissipation in the dimmer
adjuster.
Lamps start off cold with low R which has to be heated to raise the R
to the higher operating value so lamps need a good PSU in the first
second of operation to provide the higher turn on power.

Patrick Turner.

[Andre Jute[_2_]]

On Mar 3, 10:42*pm, Patrick Turner wrote:
On Mar 4, 5:06*am, Andre Jute wrote:

I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

I cannot assume the Vac is 230V and VAC could be less if there is a
transformer for a lower voltage applied to the lamp, and perhaps you
have a rectifier and Vdc applied.
But the same series R should work.

Once you know voltage and current across the globe, its R = V/I, and
to substitute the globe resistance you will need something rated for
180W.
This is not too difficult if you purchase adequate power resistors
from RS and hook them up on a remote heatsink or dangle the lot in a
bucket of oil.
Otherwise you could simply use a number of incandescent 230Vac
tungsten lamp globes in parallel, maybe 15W + 60W + 100W and with
trimming resistance all to mimic the original globe.

Low voltage lamp globes for auto use, 12V, can be seriesed if they are
all exactly the same watt rating.

I have often used light globes for dummy loads for a tube amp supply;
with a 500V supply a couple of series 60W lamps mimics 2 x KT88, and I
don't need an expensive lot of resistors which have to be large and be
kept at much lower temperatures than small amounts of muct hotter
tungsten.

But nornal incandescent laps are now banned from sale in Oz
supermarkets and all lamps sold are compact fluorescents which have
SMPS and are completely unsuitable for temporary resistors. But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used. The dimmers chop
parts out of the sine wave to effectively turn off the sine wave for
part of each cycle, and without any heat dissipation in the dimmer
adjuster.
Lamps start off cold with low R which has to be heated to raise the R
to the higher operating value so lamps need a good PSU in the first
second of operation to provide the higher turn on power.

Patrick Turner.

Thanks, Patrick. As usual, you're the firstest with the mostest. --
André

[Phil Allison[_3_]]

"Patrick Turner"

But normal incandescent laps are now banned from sale in Oz
supermarkets

** Only the "low efficiency" GLS style in 240 volt rating.

Near identical lamps with "energy saving" on the box are still available -
these use a quartz / halogen bulb inside a normal looking lamp.

All manner of low powered and high powered 240 volt incandescent lamps are
still on sale.


But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used.

** Dichroic reflector bulbs are still available everywhere - in 12 volt and
240 volt versions.


...... Phil

[Phil Allison[_3_]]

"Andre Jute"
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.


** The bulb is almost certainly a "metal halide" discharge lamp.

http://en.wikipedia.org/wiki/Metal_halide_lamp

Bit like a fluoro tube on a massive dose of steroids.



..... Phil

[Andre Jute[_2_]]

On Mar 4, 1:45*am, "Phil Allison" wrote:
"Andre Jute"

I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

** The bulb is almost certainly a "metal halide" discharge lamp.

*http://en.wikipedia.org/wiki/Metal_halide_lamp

*Bit like a fluoro tube on a massive dose of steroids.

.... *Phil

Yes, this sounds right. These two projectors were binned by a large
commercial company when the lamps reached their end of life hours,
announced by a speaking voice... Just like the voice in our Volvo
estate, until I ripped her throat.

Thanks, Phil.

Andre

[Fred[_13_]]

Patrick Turner wrote:
On Mar 4, 5:06 am, Andre Jute wrote:
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

0.078 volts? What happened to the other 229.922 volts? This resistor
isn't going in series with the globe, it's replacing the globe. OP wrote,
"I want to replace a globe in a projector with a resistor. . .".

I'd arrange to be in the next room, or better yet the next town when you
connect 230V to that 0.1 ohm resistor.

Last time I checked, 230V connected across 0.1ohms caused a current
of 2,300 amps, resulting in a total dissipation of 529 kW. You might want
to use a little bigger resistor than 5W, and hook it up with some really fat
wire. Oh, and wear shades - perhaps a welding helmet would be more
appropriate. 'Cause there's going to be some serious fireworks when you
throw the switch.

Sheeesh!

I cannot assume the Vac is 230V and VAC could be less if there is a
transformer for a lower voltage applied to the lamp, and perhaps you
have a rectifier and Vdc applied.
But the same series R should work.

Once you know voltage and current across the globe, its R = V/I, and
to substitute the globe resistance you will need something rated for
180W.
This is not too difficult if you purchase adequate power resistors
from RS and hook them up on a remote heatsink or dangle the lot in a
bucket of oil.
Otherwise you could simply use a number of incandescent 230Vac
tungsten lamp globes in parallel, maybe 15W + 60W + 100W and with
trimming resistance all to mimic the original globe.

Low voltage lamp globes for auto use, 12V, can be seriesed if they are
all exactly the same watt rating.

I have often used light globes for dummy loads for a tube amp supply;
with a 500V supply a couple of series 60W lamps mimics 2 x KT88, and I
don't need an expensive lot of resistors which have to be large and be
kept at much lower temperatures than small amounts of muct hotter
tungsten.

But nornal incandescent laps are now banned from sale in Oz
supermarkets and all lamps sold are compact fluorescents which have
SMPS and are completely unsuitable for temporary resistors. But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used. The dimmers chop
parts out of the sine wave to effectively turn off the sine wave for
part of each cycle, and without any heat dissipation in the dimmer
adjuster.
Lamps start off cold with low R which has to be heated to raise the R
to the higher operating value so lamps need a good PSU in the first
second of operation to provide the higher turn on power.

Patrick Turner.

[Phil Allison[_3_]]

"Fred"


I'd arrange to be in the next room, or better yet the next town when you
connect 230V to that 0.1 ohm resistor.

Last time I checked, 230V connected across 0.1ohms caused a current
of 2,300 amps, resulting in a total dissipation of 529 kW. You might want
to use a little bigger resistor than 5W, and hook it up with some really
fat
wire. Oh, and wear shades - perhaps a welding helmet would be more
appropriate. 'Cause there's going to be some serious fireworks when you
throw the switch.

Sheeesh!


** The dummy load resistor needs to be about 180 ohms and rated at 200
watts.

Probably cheapest to use a series string of 10 x 18 ohm, 10 watt resistors
mounted in the direct blast of a 120 mm fan.


..... Phil

[Patrick Turner]

On Mar 4, 12:30*pm, "Phil Allison" wrote:
"Patrick Turner"

But normal incandescent laps are now banned from sale in Oz
supermarkets

** Only the "low efficiency" GLS style in 240 volt rating.

Near identical lamps with "energy saving" on the box are still available -
these use a quartz / halogen bulb inside a normal looking lamp.

All manner of low powered and high powered 240 volt incandescent lamps are
still on sale.

But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used.

** *Dichroic reflector bulbs are still available everywhere - in 12 volt and
240 volt versions.

..... *Phil

Indeed one might still buy some incan decent light bulbs ( which can
dance a can-can on the head of a pin decently, voltage permitting )

But 240V ICD globes with bayonet fitting and rated over 25W have all
gone from supermarkets where 90% of ICD globes were once sold.

They have made very handy dummy loads for Pharnark Ling around with
vacuum tube PSUs.

I have switched to to fluorescent lamps with SMPS and one duz, when
the price got low enough.

It was not a bad move considering that ICD lamps would only last a
month probably because they have the Chinese Disease built into them,
ie, their quality did not include being able to put up with 255Vrms
mains which we get in Canberra on many days/evenings.

I didn't feel like putting a big fat transformer into the house wiring
circuit to drop the high mains to 210V and thus give the light bults
some reprieve from being stressed out of theit little tungsten selves.

My chinese soldering irons used to last only 1 month until I made an
outlet on a box with resistors inside to drop the voltage to 210V and
now the irons last over 2 years.
But they don't run hot enough for the new pharquing lead free solder.

Patrick Turner.

[Patrick Turner]

On Mar 4, 4:19*pm, "Fred" wrote:
Patrick Turner wrote:
On Mar 4, 5:06 am, Andre Jute wrote:
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

0.078 volts? *What happened to the other 229.922 volts? *This resistor
isn't going in series with the globe, it's replacing the globe. *OP wrote,
"I want to replace a globe in a projector with a resistor. . .".

I'd arrange to be in the next room, or better yet the next town when you
connect 230V to that 0.1 ohm resistor.

Last time I checked, 230V connected across 0.1ohms caused a current
of 2,300 amps, resulting in a total dissipation of 529 kW. *You might want
to use a little bigger resistor than 5W, and hook it up with some really fat
wire. *Oh, and wear shades - perhaps a welding helmet would be more
appropriate. *'Cause there's going to be some serious fireworks when you
throw the switch.

Sheeesh!

I suggested that the OP place a 0.1 ohm 5W wire wound R IN SERIES WITH
the existing lamp.

I don't ever recall I said to connect 230Vrms across 0.1 ohm.

If one did it would hamllessly fuse open faster than you can say
"fuse".

Patrick Turner.

[Phil Allison[_3_]]

"Patrick Turneroid"

But normal incandescent laps are now banned from sale in Oz
supermarkets

** Only the "low efficiency" GLS style in 240 volt rating.

Near identical lamps with "energy saving" on the box are still available -
these use a quartz / halogen bulb inside a normal looking lamp.

All manner of low powered and high powered 240 volt incandescent lamps are
still on sale.

But
incandescent lamps should be available at specialist lighting stores;
people still buy them for where dimmers are used.

** Dichroic reflector bulbs are still available everywhere - in 12 volt
and
240 volt versions.

But 240V ICD globes with bayonet fitting and rated over 25W have all
gone from supermarkets where 90% of ICD globes were once sold.

** Wrong.

Halogen GLS lamps with bayonet and screw fittings are sold in all
supermarkets and K-marts stores.

Go have a look at Woolworths for example.


..... Phil

[Andre Jute[_2_]]

On Mar 5, 5:37*am, flipper wrote:
On Fri, 4 Mar 2011 17:14:18 -0800 (PST), Patrick Turner

wrote:
On Mar 4, 4:19 pm, "Fred" wrote:
Patrick Turner wrote:
On Mar 4, 5:06 am, Andre Jute wrote:
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

0.078 volts? What happened to the other 229.922 volts? This resistor
isn't going in series with the globe, it's replacing the globe. OP wrote,
"I want to replace a globe in a projector with a resistor. . .".

I'd arrange to be in the next room, or better yet the next town when you
connect 230V to that 0.1 ohm resistor.

Last time I checked, 230V connected across 0.1ohms caused a current
of 2,300 amps, resulting in a total dissipation of 529 kW. You might want
to use a little bigger resistor than 5W, and hook it up with some really fat
wire. Oh, and wear shades - perhaps a welding helmet would be more
appropriate. 'Cause there's going to be some serious fireworks when you
throw the switch.

Sheeesh!

I suggested that the OP place a 0.1 ohm 5W wire wound R IN SERIES WITH
the existing lamp.

That may be what you were 'thinking' but it isn't what was said. He
asked to "replace a globe in a projector with a resistor" and you said
"I would try a 0.1 ohm x 5W."

"to REPLACE with," you would try a 0.1 ohm, resistor.

I don't ever recall I said to connect 230Vrms across 0.1 ohm.

You weren't paying attention. "Replace" is not "in series."

Gee, Flipper, Patrick and I have been corresponding for fifteen years
about high-voltage electronics. I understood he meant a two-step
operation, with the first resistor in series as a "sense" resistor to
measure across, in order to calculate a replacement for the globe.
While I agree he wasn't clear to a newbie like Fred and a literal-
minded health and safety inspector like you, I understood clearly what
he was talking about. But thanks for thinking about my continued good
health. Patrick, take notice, do better; you live too close to da
gubbermint to be careless!-- Andre Jute

[Patrick Turner]

On Mar 6, 3:00*am, Andre Jute wrote:
On Mar 5, 5:37*am, flipper wrote:





On Fri, 4 Mar 2011 17:14:18 -0800 (PST), Patrick Turner
wrote:
On Mar 4, 4:19 pm, "Fred" wrote:
Patrick Turner wrote:
On Mar 4, 5:06 am, Andre Jute wrote:
I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

I would try a 0.1 ohm x 5W wire wound R.

Usually a lamp globe watt rating is the power for normal continuous
working, Vac x Iac.

Let us suppose the voltage across the globe is 230Vac then the current
to make 180W = 180/230 = 0.783 amps ac, 50Hz.
You should read 0.078 volts ac across the 0.1 ohm resistor, and the R
dissipation would be I squared x R = 0.061 watts.

0.078 volts? What happened to the other 229.922 volts? This resistor
isn't going in series with the globe, it's replacing the globe. OP wrote,
"I want to replace a globe in a projector with a resistor. . .".

I'd arrange to be in the next room, or better yet the next town when you
connect 230V to that 0.1 ohm resistor.

Last time I checked, 230V connected across 0.1ohms caused a current
of 2,300 amps, resulting in a total dissipation of 529 kW. You might want
to use a little bigger resistor than 5W, and hook it up with some really fat
wire. Oh, and wear shades - perhaps a welding helmet would be more
appropriate. 'Cause there's going to be some serious fireworks when you
throw the switch.

Sheeesh!

I suggested that the OP place a 0.1 ohm 5W wire wound R IN SERIES WITH
the existing lamp.

That may be what you were 'thinking' but it isn't what was said. He
asked to "replace a globe in a projector with a resistor" and you said
"I would try a 0.1 ohm x 5W."

"to REPLACE with," you would try a 0.1 ohm, resistor.

I don't ever recall I said to connect 230Vrms across 0.1 ohm.

You weren't paying attention. "Replace" is not "in series."

Gee, Flipper, Patrick and I have been corresponding for fifteen years
about high-voltage electronics. I understood he meant a two-step
operation, with the first resistor in series as a "sense" resistor to
measure across, in order to calculate a replacement for the globe.
While I agree he wasn't clear to a newbie like Fred and a literal-
minded health and safety inspector like you, I understood clearly what
he was talking about. But thanks for thinking about my continued good
health. Patrick, take notice, do better; you live too close to da
gubbermint to be careless!-- Andre Jute- Hide quoted text -

- Show quoted text -

Calm down everyone,

I'm going for another bike ride later.

For one reason or another, I have not been hugely interested in the
politics just 10km away, or in the politicians of my National
Parliment to whom my favourite form of greeting is a warm "Goodbye!"
But luckily I don't live in a country where a lowly army colonel says
he cannot step down because he's just a people power person while
having nevertheless ruined all my chances of a better life and filled
the vaults of secret foreign banks with loot.
If only I could be a colonel too......http://www.friendburst.com/blog/
17845/gaddafi-international-fashion-criminal/

But I is probably lucky, The mix of having too many female guards to
zoopervise at night, too much oil, too much desert and dealing with
Foreign Powers who want oil, and coping with Al Kay- Eeda and Scottish
courts is enough to send a young groovy colonel mad and make him look
and feel ultra fugly.

I'm not sure I like the look of the people who will replace the
colonel's people.

So I need that bike ride.

Patrick Turner.

[Big Bad Bob]

On 03/03/11 18:13, Andre Jute so witilly quipped:
Yes, this sounds right. These two projectors were binned by a large
commercial company when the lamps reached their end of life hours,
announced by a speaking voice... Just like the voice in our Volvo
estate, until I ripped her throat.

a nagging car? Ew. No wonder some people change the vowels to describe
a 'Volvo'.

[Andre Jute[_2_]]

On Mar 7, 9:01*pm, Big Bad Bob BigBadBob-at-mrp3-
wrote:
On 03/03/11 18:13, Andre Jute so witilly quipped:

Yes, this sounds right. These two projectors were binned by a large
commercial company when the lamps reached their end of life hours,
announced by a speaking voice... Just like the voice in our Volvo
estate, until I ripped her throat.

a nagging car? *Ew. *No wonder some people change the vowels to describe
a 'Volvo'.

You're BAD, Big Bob.

[Big Bad Bob]

On 03/08/11 14:11, Andre Jute so witilly quipped:
On Mar 7, 9:01 pm, Big Bad BobBigBadBob-at-mrp3-
wrote:
On 03/03/11 18:13, Andre Jute so witilly quipped:

Yes, this sounds right. These two projectors were binned by a large
commercial company when the lamps reached their end of life hours,
announced by a speaking voice... Just like the voice in our Volvo
estate, until I ripped her throat.

a nagging car? Ew. No wonder some people change the vowels to describe
a 'Volvo'.

You're BAD, Big Bob.

yes. yes I am.

[Vance_Iam]

Originally Posted by Andre Jute[_2_]

I want to replace a globe in a projector with a resistor for
experiments with micromirrors built into the box. I can't measure the
hot resistance of the globe, because I can't get in. The globe is
rated 180W and it's some type of mercury vapor. At the moment the box
is away for mods, so that's all the info I have.

Two questions here. What value resistor, and what rating?

And no, I haven't yet worked out whether just bypassing the globe,
like bypassing a switch, will do the job.

Andre Jute

Dear Andre, What are you as professional... I want to know you profession.... even though, I am interested in electrical but can't proceed. Your suggestions and advise will be valuable for me...Consult with a professional electrician or engineer for you problem.thanx


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