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.