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Old September 28th 13, 01:48 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED


"William Sommer******"

I'd like to point out that is no such thing as -- nor can there be -- a
white LED. LEDs are necessarily limited to a narrow band of wavelengths. *
All (???) white LEDs are (I assume) a blue LED with a yellow-fluorescing
phosphor. **

This /looks/ white to the eye, but the red and green wavelengths needed
for color reproduction aren't present.



** As ****ing usual, the Somer****** fool just makes stuff up.

Anyone can Google "white led" and get the facts.

There is plenty of green orange and red in the light from regular white
leds.


..... Phil



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Old September 28th 13, 03:28 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED



"N_Cook" wrote in message
...
Assuming over-riding the opto couplers to falsely confirm to the system
micro that the arc is struck and the lamp is lit (maybe requiring a delay)
firstly, with the lamp ps disconnected.
Then I intend in the first instance to buy 5x 1.2W white LEDs, 3500K, 20
degree, for proof of concept. Assuming that sort of works then get perhaps
10 more, going down to 2700K or 3000K or perhaps (unlikely) 4000K and
lenses to colimate to 2 degrees. Set inside a reversed conical silvered
glass of an ex-lamp to direct spillover light into the colourwheel/light
tunnel aperture.
The intended LEDs are 11x10mm footprint so can be mounted quite close to
the colourwheel(for 5 anyway) on a spherical back mount. I may as well
retain the original fans, perhapps knocked back a bit for less noise
intrusion later on.

When coming to scaling up I originally was thinking of using a sectored
curvi-linear silvered reflector from PIR units (with faned air cooling)
but have since come across 2 degree lens converters for these LEDs so may
as well go with them and shine directly from a larger spherical backing
mount, directly to the colourwheel aperture.

I'd be interested in any suggestions or comments other than of the I would
not bother type of replies.


Sorry to be one of those people, but based on some experiments that I've
recently been doing with high power LEDs, I think you are going to be
****ing in the wind. A few watts worth is not going to come close. I have
been playing with some 10 watt types with appropriate collimating reflectors
and lenses. Whilst they are 'blinding' to look at directly, you could easily
do it with a pair of sunglasses on. You most certainly could not do that
with a 200 watt discharge lamp. Also, they require substantial amounts of
directly fan-cooled heatsinking, which makes the assembly physically quite
large. A further problem with high power LEDs, is that they are made from
multiple chips on a single die. This actually makes it rather difficult to
get an even density light from them. Because they are substantially
flat-plane light radiators, the light tends to remain in 'dots' through the
collimating and focusing optics.

I do a lot of work on pro and semi pro lighting fixtures - such as moving
heads of the type that you see in use on TV shows like Strictly and
X-Factor. The ones at the small to medium end typically use discharge lamps
in the range 150 to 575 watts. There are now some at the lower end of the
market which use LEDs, and I can tell you that no matter how powerful a LED
that they employ, they cannot hold a candle (Ha!) to the 'real deal' with a
discharge lamp in them.

So, whilst you may get some results that are just about acceptable in the
right circumstances, I honestly feel, based on practical experience, that
you will get anywhere near matching the performance of the discharge lamp
originally fitted.

Arfa

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Old September 28th 13, 03:33 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED



"N_Cook" wrote in message
...
On 27/09/2013 14:46, William Sommerwerck wrote:
Have you calculated whether you can cram enough LEDs into that space to
get the same brightness level as the discharge lamp? Or are you
expecting to learn from the test?

I'd like to point out that is no such thing as -- nor can there be -- a
white LED. LEDs are necessarily limited to a narrow band of wavelengths.
* All (???) white LEDs are (I assume) a blue LED with a
yellow-fluorescing phosphor. **

This /looks/ white to the eye, but the red and green wavelengths needed
for color reproduction aren't present.

Unless your white LEDs contain red, green, and blue LEDs, I don't think
this is going to work.

* This is actually a good thing if one is trying to match a specific
color space, and you can manufacture LEDs whose wavelengths correspond
to the three primaries.

** I'm thinking of indicator lights and such. Lamps to replace
incandescent lighting would necessarily have to put out red and green,
or colors wouldn't look right.


I've had another look at the product data and the 2 degree lenses are 4
degree , in normal terminology

I don't know what chromaticity means but for the 3500 deg K version a Cx
of about .4 and Cy of about .39
A bit more graphic the spectrum is continuous and smooth "bell curve" peak
shifted 40nm from 550nm of the standard eye response curve to 590nm
and the 50% points broader apart at 150nm compared to 100nm of the eye and
a 50% down peak at 460nm which I suppose is the potential bugbear for such
a lamp conversion


That triangular diagram that you see with red, green and blue respectively
at each corner and white in the middle, and intended to show every possible
colour that can be derived from additive mixing of those three colours, is
called a chromaticity diagram. It famously used to be used to show that a
colour CRT cannot (truly) produce brown.

Arfa

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Old September 28th 13, 03:38 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED



"N_Cook" wrote in message
...
On 27/09/2013 18:35, Jeff Liebermann wrote:
On Fri, 27 Sep 2013 14:34:59 +0100, N_Cook wrote:

Then I intend in the first instance to buy 5x 1.2W white LEDs, 3500K, 20
degree, for proof of concept. (...)


I've done this with marginal sucess. The problem is focus. The
original light has all the light coming from roughly a single point.
An array of 5 LED's will distribute the light over a much larger area.
It will work well with light from the central LED using the original
reflector, but the outer LED's will be wasted and splattered all over
the room.

You don't really need the original reflector if the light source has
its own forward facing reflector. Try cramming an MR16 bulb in place
of the projector bulb and reflector. The smaller size MR16 lamps
might fit.

Mo
http://www.instructables.com/answers/Change-a-projector-lamp-to-LED-/


All the discharge lamps in video projectors , I/ve seen have an electrode
and squashed , not optically conductive glass, axial exactly in line to
where you want the light to go.
With directional 20 degree central LEDs, and lensed 4 degree ones
off-axis. will direct most of the energy directly to the half inch
aperature , without any reflectors . Reflectors just to mop up spill over
.
I can see some high power red LEDs being added to counter the blue
sub=peak


My experiments have shown that the use of a collimating reflector
specifically designed for the LED package being used, brightens the forward
beam significantly ...

Arfa

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Old September 28th 13, 03:41 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

"Arfa Daily" wrote in message ...

That triangular diagram with red, green and blue at the corners
and white in the middle, and intended to show every possible colour that can
be derived from additive mixing of those three
colours, is called a chromaticity diagram. It famously used to be
used to show that a colour CRT cannot (truly) produce brown.


You've never seen a '70s RCA set? Brown was about the only color it /could/
produce (along with some blues and yellows, if I recall correctly).

Brown is actually a very dark red.



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Old September 28th 13, 10:44 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

On 28/09/2013 02:28, Arfa Daily wrote:


"N_Cook" wrote in message
...
Assuming over-riding the opto couplers to falsely confirm to the
system micro that the arc is struck and the lamp is lit (maybe
requiring a delay) firstly, with the lamp ps disconnected.
Then I intend in the first instance to buy 5x 1.2W white LEDs, 3500K,
20 degree, for proof of concept. Assuming that sort of works then get
perhaps 10 more, going down to 2700K or 3000K or perhaps (unlikely)
4000K and lenses to colimate to 2 degrees. Set inside a reversed
conical silvered glass of an ex-lamp to direct spillover light into
the colourwheel/light tunnel aperture.
The intended LEDs are 11x10mm footprint so can be mounted quite close
to the colourwheel(for 5 anyway) on a spherical back mount. I may as
well retain the original fans, perhapps knocked back a bit for less
noise intrusion later on.

When coming to scaling up I originally was thinking of using a
sectored curvi-linear silvered reflector from PIR units (with faned
air cooling) but have since come across 2 degree lens converters for
these LEDs so may as well go with them and shine directly from a
larger spherical backing mount, directly to the colourwheel aperture.

I'd be interested in any suggestions or comments other than of the I
would not bother type of replies.


Sorry to be one of those people, but based on some experiments that I've
recently been doing with high power LEDs, I think you are going to be
****ing in the wind. A few watts worth is not going to come close. I
have been playing with some 10 watt types with appropriate collimating
reflectors and lenses. Whilst they are 'blinding' to look at directly,
you could easily do it with a pair of sunglasses on. You most certainly
could not do that with a 200 watt discharge lamp. Also, they require
substantial amounts of directly fan-cooled heatsinking, which makes the
assembly physically quite large. A further problem with high power LEDs,
is that they are made from multiple chips on a single die. This actually
makes it rather difficult to get an even density light from them.
Because they are substantially flat-plane light radiators, the light
tends to remain in 'dots' through the collimating and focusing optics.

I do a lot of work on pro and semi pro lighting fixtures - such as
moving heads of the type that you see in use on TV shows like Strictly
and X-Factor. The ones at the small to medium end typically use
discharge lamps in the range 150 to 575 watts. There are now some at the
lower end of the market which use LEDs, and I can tell you that no
matter how powerful a LED that they employ, they cannot hold a candle
(Ha!) to the 'real deal' with a discharge lamp in them.

So, whilst you may get some results that are just about acceptable in
the right circumstances, I honestly feel, based on practical experience,
that you will get anywhere near matching the performance of the
discharge lamp originally fitted.

Arfa


Have you tried the video projector use rather than Gobo type things
where you are not trying to squeeze light along a small aperature light
tunnel? I've not found the data out there but I suspect the vast
majority of the light available to a gobo setup just does not get into a
light tunnel setup , so if you can direct all your LED lamps into that
tunnel then the overall requirement is much lower than normal ratings
would suggest.
The use of this video projector is for text and graphics so colour
rendition of the likes of flesh tones is not too critical, very rarely
showing any video as such.
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Old September 28th 13, 11:27 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

On 27/09/2013 18:43, William Sommerwerck wrote:
Could you send me the data sheet, or its URL?
I'd like to take a look.


http://www.promelec.ru/pdf/LCWW51M.pdf


I'm not an expert on this subject (though I do know a little). My gut
reaction
is this...

The color reproduction index is only 80. That's poor. That doesn't mean
that
the LED won't work -- but it will probably need appropriate filtering that
won't be easy to achieve.

The spectral emission (p11) isn't particularly flat -- and definitely not
smooth -- no doubt one of the reasons for the poor CRI.

I don't think you're going to get pleasing results.


Intended use in the main part is for projecting text and graphics so as
long as there is a colour difference, any colour difference almost,
rather than correct colour rendering that is all that is required , a
rare pic with a green flesh tone or something does not really matter too
much

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Old September 28th 13, 05:59 PM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

I've moved away from thinking about using lenses as they restrict the
footprint size. If I double stack the LEDs then a spacing of centres
about 8.5mm is possible and so 14 LEDs in a 32mm diameter. So can be
quite close to the light tunnel and 20 degree beam spread is fine and
outer LEDs approach angle will still only be 30 degrees or so, and a
reasonable proportion of that will reflect only a few times and
substantially get to the DLP chip. Will still try 5 LEDs initially.
Will power up individually at only 100mA or so and set the angles of
each individual LED for maximum brightness at a simulated window with a
photodiode , then wire all in series and make a more substantial back
mount before transfering to the projector
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Old September 28th 13, 11:08 PM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

On 27/09/2013 11:34 PM, N_Cook wrote:
Assuming over-riding the opto couplers to falsely confirm to the system
micro that the arc is struck and the lamp is lit (maybe requiring a
delay) firstly, with the lamp ps disconnected.
Then I intend in the first instance to buy 5x 1.2W white LEDs, 3500K, 20
degree, for proof of concept. Assuming that sort of works then get
perhaps 10 more, going down to 2700K or 3000K or perhaps (unlikely)
4000K and lenses to colimate to 2 degrees. Set inside a reversed conical
silvered glass of an ex-lamp to direct spillover light into the
colourwheel/light tunnel aperture.
The intended LEDs are 11x10mm footprint so can be mounted quite close to
the colourwheel(for 5 anyway) on a spherical back mount. I may as well
retain the original fans, perhapps knocked back a bit for less noise
intrusion later on.

When coming to scaling up I originally was thinking of using a sectored
curvi-linear silvered reflector from PIR units (with faned air cooling)
but have since come across 2 degree lens converters for these LEDs so
may as well go with them and shine directly from a larger spherical
backing mount, directly to the colourwheel aperture.

I'd be interested in any suggestions or comments other than of the I
would not bother type of replies. Anyone happen to know what the light
wastage proportion is of a non-ideal paraboloid reflector and non-point
source discharge lamp is? I'm aware proper LED projectors have active
drives to RGB LEDs and not colour wheels but there are a lot of
ink-jet-printer-syndrome surplus HD video projectors around with too
expensive short-arc lamp costs to replace

Some bods been here before with converting a couple of types of
discharge lamp converters
http://www.blue-room.org.uk/index.php?showtopic=54833
http://www.blue-room.org.uk/index.ph...#entry4265 04


If anyone is interested, my exploration of inside a standard domestic
GU10 LED lamp (to see if they were all in series or mixed series/parallel)
240V,2W.
Breaking in:- hold the bulb in a glove and heat the dome cover with
"low" temp hot air and prize off with a needle. With old soldering iron
destroy the epoxy join between the , not obvious as silvered, pcb to the
lamp housing. The slight greeen colouration is due to the reflection of
the green dye of the pcb which is not glass fibre reinforced it seems,
maybe epoxy substrate only. Prize the pcb away.
No glass breakage at any stage.
Overlay of this one marked JH-GU10-20
HV ac side 1M//0.33uF 400V dropper and 1/4W resistor size
fuse/inductor/fuseable resistor? pink colour with red black brown, or
reverse order, colour bands, about 0.4R to small SMD MB6S bridge
rectifier.
LV quasi-DC side SMD 510R dropper to 20 LEDs in series.
White ceramic cap is cemented to the glass of the lamp.
Bench ps 50V across LED string and 510R all LEDs just lit
54V and 0.5V over 510R and about 2.6V over each LED some sort of low
level brightness.
With 75% mains (240V that is) 6.5V DVM dc over 510R
or 5.5V DVM ac over 510R
100% mains 9.1V "DC" or 7.2V as "AC" reading over the 510R


**What a waste of time and effort. The best LEDs are approximately
similar efficiency to that of halide lamps. As others have stated, the
big problem will be that you are substituting a compact light source
with a rather diffuse one. The optics are not designed for such use.

--
Trevor Wilson www.rageaudio.com.au
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Old September 29th 13, 09:50 AM posted to sci.electronics.repair
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Default Converting a 200W discharge lamp video projector to LED

On 28/09/2013 22:08, Trevor Wilson wrote:
On 27/09/2013 11:34 PM, N_Cook wrote:




**What a waste of time and effort. The best LEDs are approximately
similar efficiency to that of halide lamps. As others have stated, the
big problem will be that you are substituting a compact light source
with a rather diffuse one. The optics are not designed for such use.


But the lamps used in video projectors are ,in effect, not compact. The
direct light path from the reasonably compact source is blocked by an
electrode and non optical structural glass lump, relying on the mirror
surface of the light tunnel / light pipe to average out/balance-up the
light coming in at all sorts of angles, off the parabaloid reflector


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