How to find super bright, white, LEDs?

[[email protected]]

Hi,

I work in a nightclub and we have a bunch of old moving lights that still work
okay except for lamp problems. They use arc lamps and it's not worth the cost it
would take to get them in condition to fire the lamps again, plus there is the
cost of the lamps, the cost of electricity to run them, and the damage that the
heat does... I would like to try finding a really bright white LED light source
to see if we can position it and make it work in our fixtures, if that's a
practical thing to attempt. Can anyone tell me where I can find some bright LED
light sources that might be suitable to try?

Thanks for any help!
David

 

[William Sommerwerck]

You want to replace arc lamps with LEDs?

!!!!!!!!!!!!!!!!!

 

[JB]

Hi,

I work in a nightclub and we have a bunch of old moving lights that still
work
okay except for lamp problems. They use arc lamps and it's not worth the
cost it
would take to get them in condition to fire the lamps again, plus there is
the
cost of the lamps, the cost of electricity to run them, and the damage
that the
heat does... I would like to try finding a really bright white LED light
source
to see if we can position it and make it work in our fixtures, if that's a
practical thing to attempt. Can anyone tell me where I can find some
bright LED
light sources that might be suitable to try?

Sadly the optics in these type of 'moving light' projectors are not suited
to an LED retrofit, either optically or thermally. Quite apart from the the
high lumen output of the high pressure lamps currently in your projectors
[at least 10x to 20x that of a typical high power LED array], the arc size
is extremely small to facilitate good optical control [an LED array of the
similar lumens would be ~50mm diameter and useless for imaging optics].
Basically an optical system has to be designed specifically for an LED
source for it to work correctly. The optics in your projectors are designed
specifically for short-arc, high pressure metal halide or ultra high
pressure mercury lamps, and are superb at what they do. Although as you
rightly say, the maintenenace isn't cheap.

JB

 

[BeeJ]

Try contacting Cary Eskow at Avnet LightSpeed.
He seem very knowledgeable on the subject of LEDs.
e-mail Cary at
[email protected]

--
So where are we?
Not the street address.
Not the city.
Not the country.
Not the Earth.
Not the Solar System.
Not the Galaxy.
Not the Universe.
Not the Brane.
So where is the Brane?
Where are we?

Life is but a dream!

 

[N_Cook]

Hi,

I work in a nightclub and we have a bunch of old moving lights that still
work
okay except for lamp problems. They use arc lamps and it's not worth the
cost it
would take to get them in condition to fire the lamps again, plus there
is the
cost of the lamps, the cost of electricity to run them, and the damage
that the
heat does... I would like to try finding a really bright white LED light
source
to see if we can position it and make it work in our fixtures, if that's
a
practical thing to attempt. Can anyone tell me where I can find some
bright LED
light sources that might be suitable to try?

Sadly the optics in these type of 'moving light' projectors are not suited
to an LED retrofit, either optically or thermally. Quite apart from the
the high lumen output of the high pressure lamps currently in your
projectors [at least 10x to 20x that of a typical high power LED array],
the arc size is extremely small to facilitate good optical control [an LED
array of the similar lumens would be ~50mm diameter and useless for
imaging optics].
Basically an optical system has to be designed specifically for an LED
source for it to work correctly. The optics in your projectors are
designed specifically for short-arc, high pressure metal halide or ultra
high pressure mercury lamps, and are superb at what they do. Although as
you rightly say, the maintenenace isn't cheap.

JB

I work on these short arc discharge lamped moving heads, and it depends on
who makes them as to how expensive they are to repair. Some that I service
use electronic ballasts to control the lamp, and these are effectively quite
complex switch mode power supplies that produce around 100 volts AC at
anything up to 15 amps, depending on the power of the fitted lamp. They can
be quite challenging in terms of time, to get going again when they fail.
Parts-wise, they don't tend to use anything too special that you wouldn't
find in switchers in a more conventional application. Most of these units
also have another switcher in them to produce the DC volts for the DMX
control board, as well as the supplies for the stepper motor drivers

there's a lot of motors in them to control pan, tilt, gobo selection, filter
selection, zoom, focus etc). Generally, these power supplies are pretty
conventional, and reliable. The motor driver boards fail, but again, they
are fairly straightforward, and not expensive, parts-wise, to repair.

Some other makes make use of conventional choke ballasts for controlling the
lamp, and these tend to be very straightforward. Often, the lamp igniter is
a sealed module, but some use discrete parts.

As to lamps, if you take the time to cast around on the net a bit, you can
reduce the silly money that some suppliers want for them, down to very
sensible levels. For sure, you will probably be buying a no-name rather than
a genuine Philips say, but it will perform just the same, and last nearly as
long.

As to modifying these lights to take a high power LED, I agree with JB's
summary - it's a non-starter. I think that you should take the trouble to
repair and refurbish them if you have the capability, or if not, at least
enquire what the cost of a professional repair on them would be.

Arfa

Do you buy 10 or so at a time compact (air cooled) "bare" discharge lamps
from hk/cn and build into the original reflectors ?

 

[JB]

http://electronics.mcmelectronics.com/?N=&Ntt=led+lights&x=0&y=0

OK for home use or even a small function in a dark pub but *nowhere* near
enough lumens for serious use in a club/disco/stage environment.
Looking at the data, it's 20W [presumeably RGB] LED array is likely to
produce no more than 500-800Lm. This is not going to compare well with even
low power HID projectors with sources of >20x this lumen output.
I've seen a prototype RGB LED source in a lab in the Netherlands last year
with an output of ~10kLm, intended for moving light projectors. This was a
liquid cooled beast of >300W but very compact in optical dimensions. With a
purpose designed optical system, this would be a good HID equivalent, but
still couldn't compete with the really 'big boys', the 575/700/1200W powered
monsters!

JB

 

[N_Cook]

Is that addressed to me ? Not sure that I'm following exactly what you're
asking ?? Are you assuming that these particular lamps come built into a
reflector assembly like the ones that go in back-projector TVs for instance
? If so, the answer is no. These moving heads have the reflector as part of
the fixed optics. The lamp is 'bare' and fits into a ceramic holder that is
then fixed in some way behind the reflector, such that the lamp pokes
through the centre hole in the reflector to a distance where the internal
quartz glass discharge tube sits at the focal point. Some of the higher
powered lamps have a screw connection at either end and a bulge in the outer
envelope over the discharge tube. These fit in a simple clamp that holds the
discharge area of the lamp at the focal point of the reflector.

Google for instance MSD 250 and HTI 1200 to see pictures

Arfa

So more like the more standardised industrial floodlight application and
consequential sensible pricing. Rather than the compactified projector TV
situation of somewhat power-for-power standardised bare bulbs, but cemented
into myriad shapes and sizes of reflectors that then fit and connect into
customised enclosures

 

[[email protected]]

These moving heads have the reflector as part of
the fixed optics. The lamp is 'bare' and fits into a ceramic holder that is
then fixed in some way behind the reflector, such that the lamp pokes
through the centre hole in the reflector to a distance where the internal
quartz glass discharge tube sits at the focal point.

That's the idea I'd like to try. We have two Chauvet Q Spots that do something
similar with a bright white LED, though I doubt the particular LED they use
would be bright enough. It seems to be mounted directly to a heat sink if I
remember right, and if it *has* to be mounted on a heat sink that would be a big
problem. But if it could be mounted on an extending piece of metal even if it
has to be perforated or whatever, it seems it could then be put through the
reflector and positioned wherever it needs to be. It would take some thought and
work to make such an adaptor, but then the fixture would be good to go again
using a lot less power, creating a lot less heat and the resulting damage from
heat, and there would be no need to buy bulbs again instead of every six months
or so. Also fixtures wouldn't be shut down by problems with lamping on, which is
the biggest problem we have with our fixtures. From what I understand, two of
our electronic ballast Mac 500s are not worth fixing because the ballast costs
$1300+, even though the rest of both fixtures seem to be in good condition.

Something else. The Mac 101s kick ass with a nice solid beam in pretty much all
colors. Do you know what wattage LEDs they are? Someone told me 3 watt, but I
haven't been able to find where it says that specifically. Anyway, I would like
to find some LED "par can" type fixtures that put out a similar beam, and I've
seen 3 watt LED pars advertised but don't know if it would be the same or not.
The idea is that if we can get some of those, we could strip our old messed up
600s down pretty much to the frame and mount the LED pars in them to get
something similar to the 101s. They would be run as two different fixtures, but
we'd only have to fool with pan and tilt on the 600s part... So do you know of
any LED pars, the cheap type from China, that might do the job? Or what
specifically I should look for in an attempt to find them?

 

[[email protected]]

That is a very reasonable question and goal.
There are a number of available LED-based lights and spotlights that
can be adapted to use as replacements for a goodly number of arc-lamp
applications.

What do you understand by arc-light ? Two carbon electrodes running at
full atmospheric pressure (possibly by some wind shielding) or
something else ?

Most light output from the 1880's arc street lamps was due to the hot
electrodes and not much from the arc itself (mostly UV).

Film studios used arc lamps during the silent film era, but caused a
lot of eye problems to the actors due to the UV radiation.

But after the 1930's anyone actually using arc-lamps for illumination
purposes ?

Sure, as a kid I have experimented using the carbon core of a D-size
battery as an arc light electrode running from 220 V with some current
limiting, but after a while, this was not too interesting :-(

 

[William Sommerwerck]

What do you understand by arc-light? Two carbon

electrodes running at full atmospheric pressure
(possibly by some wind shielding) or something else?

The former. The question seemed absurd!

But after the 1930's is anyone actually using arc-lamps
for illumination purposes?

How do you defrine "illumination"? Aren't they still used to promote major
events?

 

[Chiron]

Most light output from the 1880's arc street lamps was due to the hot
electrodes and not much from the arc itself (mostly UV).

Film studios used arc lamps during the silent film era, but caused a lot
of eye problems to the actors due to the UV radiation.

But after the 1930's anyone actually using arc-lamps for illumination
purposes ?

Sure, as a kid I have experimented using the carbon core of a D-size
battery as an arc light electrode running from 220 V with some current
limiting, but after a while, this was not too interesting :-(

I was a movie theater usher back in the 1970's. The projectors used
carbon arc lamps. Not sure if that counts as being for "illumination,"
though...

 

[[email protected]]

What do you understand by arc-light ? Two carbon electrodes running at
full atmospheric pressure (possibly by some wind shielding) or
something else ?

Most light output from the 1880's arc street lamps was due to the hot
electrodes and not much from the arc itself (mostly UV).

Film studios used arc lamps during the silent film era, but caused a
lot of eye problems to the actors due to the UV radiation.

But after the 1930's anyone actually using arc-lamps for illumination
purposes ?

http://is.gd/M9ayip

 

[N_Cook]

Yes, pretty much. Google those two types that I said, and you will see
exactly what they look like. Twenty to forty quid for a no-name, depending
on power rating. A bit more for a Philips or Osram

Arfa

compared to the 300 or 400 squid for the much the same active element
fire-cemented into a customised reflector for a projection system

 

[William Sommerwerck]

I keep seeing mention of carbon arc lamps popping up

in the thread. Where do these come into the equation?

They came into the equation when the original poster used the term "arc
lamp".

As the article says... "In popular use, the term arc lamp means carbon arc
lamp only."

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

 

[Ralph Wade Phillips]

But after the 1930's anyone actually using arc-lamps for illumination
purposes ?

Sure, as a kid I have experimented using the carbon core of a D-size
battery as an arc light electrode running from 220 V with some current
limiting, but after a while, this was not too interesting :-(

Ahem.

Google High Intensity Discharge (HID) lights sometimes.

Then look at the front of most modern vehicles.

RwP

 

[William Sommerwerck]

I keep seeing mention of carbon arc lamps popping up

Ah, I see. A misunderstanding of the OP's not-quite-precise
definition of his lamp type. He was of course referring to a
short-arc discharge lamp, which is a fundamentally AC device,
with an arc maintained between a pair of tungsten electrodes
set into a gas-filled quartz discharge tube, as opposed to a pair
of carbon rods normally fed from a low voltage high current DC
source.

I'm not sure that the Wiki article is strictly up to date with the
technology, as surely, any lamp based on an arc being
maintained between two electrodes, irrespective of the specific
technology involved, must qualify in strict definition, as an
"arc lamp", mustn't it?

Yes, and that's /exactly/ what the article says. All lamps -- including
fluorescents -- that strike an arc between electrodes, are arc lamps. Note
the phrasing -- "In popular use..."

I'm glad I read the article. (I even rewrote bits of it.) I didn't know how
ballasts are used to start a fluorescent. (I'm still confused as to how a
device in parallel with the lamp can limit current through it. But let's not
get started.)

 

[N_Cook]

For a video projector system where the illumination is directed down a
mirrored light tunnel onto the active silicon DLP or whatever , I wonder how
much light is wasted from a mercury arc source and a reflector. The ones
I've seen the area of the colour wheel / light tunnel is perhaps 10 percent
of the open aperture end of the reflector and as the bulb is not a point
source perhaps only something like 10 percent is used.
With a bank of LEDs the directionality is ideal , you can mount on the
surcace of a sphere and direct them all , individually , at the wanted area.