# LED questions... My dissertation - Stage lighting!



## foo_fighter4000 (Feb 13, 2006)

Right, hello!

I'm a final year product design student in Bristol, UK and im looking at the possibilities of LED stage lighting for small live venues... Im at the stage in the project where i need to know what would need to go into the light...

Im looking at fairly small lighting systems on the scale of things... im estimating about 50 LED's at this stage but that could quite easily change....

Im fairly new to electronics and have only a basic understanding and background so please try to explain! 

So yeah what im asking is exactly what would need to go into something like this:

http://www.chamaeleon-tech.com/Dionysus_PAR196.htm

Thanks in advance for any help! 

Ps remember im in the UK so we use different voltages/amps etc (if this matters!)

:goodjob:


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## cheapo (Feb 13, 2006)

well, I personally would use lux Vs, but maybe 5mms would be cheaper. The lux Vs are VERY bright when driven at 5 watts, and you would only need about 1/100th the amount of LEDs.

-david


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## Ken_McE (Feb 13, 2006)

So what you are after is an RGB LED flood/spotlight that would run off mains voltage? How many lumens do you need it to produce? What is the cost of a comparable incan. spot/floodlight and some theatrical gels?


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## Wim Hertog (Feb 13, 2006)

First, have a look at this thread: https://www.candlepowerforums.com/threads/106793

For the moment I'm designing a 200 superflux based RGBW floodlight. This produces a nice amount of light, but nowhere near the amount needed for stage lighting.

Please drop me an email if you want more info!


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## markus_i (Feb 14, 2006)

Hi Wim,

regarding the light you spoke of:
- the LEDs as mentioned on the product page
- a power supply, converting the 230 VAC to something manageable
- a microcontroller for decoding the 7 DMX channels (and possibly performing some operations to change/mix the light's output with respect to the DMX input, although this could as well be done in the master controller)
- presumably 7 driver stages
- connectors for power and control
- probably a fan
- various labels stating the conformance with the locally applicable regulations (only half joking - at least some conformance testing must be done on such things, especially in .eu)
- some engineering (not too much for a company that already has the DMX decoders on file)

Just guessing, mind you. Why don't you ask the manufacturer?

Bye
Markus


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## Wim Hertog (Feb 14, 2006)

markus_i said:


> Hi Wim,
> 
> regarding the light you spoke of:
> 
> Markus




Euhmm....I (Wim) was not the original poster

Anyway, what you said is right. My RGBW floodlight will contain:

- A 12V regulator circuit (no 230V supply)
- Red, Green, Blue and White superflux LEDs (200 pcs)
- A CPLD, because I have all the programming hardware at home...and it's faster than a microcontroller.
- Mosfet driver stage
- Fan 
- control buttons

I did not implement DMX, as I have no DMX control panel available.

All the compliance testing is not really necessary for a small project


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## foo_fighter4000 (Feb 14, 2006)

I *think* im looking at predominantly white led's and use of coloured filters... however this may change depending on a number of things....

 

Yes it needs to run off mains voltage, preferably using something like a kettle lead in the back so i guess id need a built in psu. 

 

Cost is not really decided yet - im still looking into it! Same with lumens... im not entirely sure how many would be needed...

 

Im not much use really... completely new to lighting technology... ive only really used them as a consumer - never looked too deeply into them!

 

Forgive my naivety but what are LuxVs?!

 

Thanks again, James


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## markdi (Feb 14, 2006)

I think it was dr. Edwin land(polaroid) that discovered that white light could be made by mixing blue and green light.

so I think you will get very little red from white led's.


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## Wim Hertog (Feb 14, 2006)

foo_fighter4000 said:


> I *think* im looking at predominantly white led's and use of coloured filters... however this may change depending on a number of things....
> 
> 
> 
> ...




White LEDs and color filters are completely useless. The benefit of using Red, green and blue LEDs is the ABSENCE of light eating color filters. 

Using red, green and blue LEDs increases efficiency and color purity very much. 

A built in PSU is no problem. You can use a small laptop switcher for example.

LuxV are 5 watt LEDs from lumileds. If I were you, however, I would use normal 5mm LEDS (with large beam angle). They are much better value than the LuxV's. 50 good LEDs will cost you no more than 15-20 pounds.


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## Wim Hertog (Feb 14, 2006)

markdi said:


> I think it was dr. Edwin land(polaroid) that discovered that white light could be made by mixing blue and green light.
> 
> so I think you will get very little red from white led's.



White LEDs create white light by mixing monochromatic blue (LED) with a broadband yellow emission (YAG phosphor). The yellow phosphor peaks at 550 nm (green) and slowly rolls of to +- 700 nm. Red is present, but due to the high color temperature of most white LEDs, emission of red light is quite low.

Mixing blue and green light gives cyan (= bluish green)


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## foo_fighter4000 (Feb 15, 2006)

Wim Hertog said:


> White LEDs and color filters are completely useless. The benefit of using Red, green and blue LEDs is the ABSENCE of light eating color filters.
> 
> Using red, green and blue LEDs increases efficiency and color purity very much.
> 
> ...


 
Right so your saying use RGB, in this case will 50 be enough? i wasnt sure if id get a strong enough beam from 50 RGB whereas 50 white's and filters should be strong enough? I do see what you mean about filters tho and yes good point.

So an inbuilt psu needs to be no bigger than a laptop battery? how small could it be? Im trying to keep the unit as small as poss - hence only wanting to use around 50 LED's... that way a set of them are much more portable and as they only have to light a small venue - should be viable.

Cheers


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## markus_i (Feb 15, 2006)

Wim,

sorry for the mix-up - I can only guess that I was confused from the reverse-ordering of the post in the reply window.

foo-fighter,

at one point, you'll either need to build a prototype in order to see how much light you actually need or supply some numbers w/ respect to what you want, i.e.
- how small is the small venue
- how far away from the stage are the lights
- what kind of overall illumination is necessary

LEDs won't give you very much light for the size - halogen and HDI are better at that. LEDs also won't give you the sharp spotlights you can get from gas discharge lights (the emitter area is simply too large). LEDs are excellent for colour mixing (if you use RGB(W) modules), robustness and lifetime.

Regarding the size of the PSU - that depends on your requirements regarding light output, the amount of money you want to spend and the safety (and cooling) provided by the enclosure of the light. Under the right circumstances, matchbox-size would be a bit ambitious (but possible), the size of a cigarette pack definitely within range of an industrial standard module.

Another question would be: how many individual lights will your setup tolerate? If you go for an external PSU (keep the supply to the lights at industrial safe voltage levels, e.g. 42 VDC), there's no reason why a light with ~200 5mm LEDs (no additional optics, although you'll probably want some flaps on the sides) should be larger than two cigarette packs stacked - in which case your main problem will be all those cables needed to connect a few dozen lights to your controller ;-)

Bye
Markus


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## foo_fighter4000 (Feb 16, 2006)

So do you reckon its possible to get enough light out of a mixture of red, green and blue LED's yet keeping the total numbers under 50??? I want to keep the unit really as small as poss!

One other thing - if i put these 50 LED's (between 20,000 and 40,000mCd's each) as well as the power supply/power converter into a small box - say no bigger than 10x10x10cm - would it need cooling? if so would they need a fan or could i get away with a heatsink?

Thanks again!


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## Wim Hertog (Feb 16, 2006)

foo_fighter4000 said:


> So do you reckon its possible to get enough light out of a mixture of red, green and blue LED's yet keeping the total numbers under 50??? I want to keep the unit really as small as poss!
> 
> One other thing - if i put these 50 LED's (between 20,000 and 40,000mCd's each) as well as the power supply/power converter into a small box - say no bigger than 10x10x10cm - would it need cooling? if so would they need a fan or could i get away with a heatsink?
> 
> Thanks again!



No, you won't get enough light for real stage lighting. 50 LEDs can provide "mood" lighting at home, but not on stage. 

If the plan is to provide general mood lighting on stage and you're planning to use multiple units....than this may work out.

If the unit is constantly cycling through colors (not all the LEDs are on all the time), you can probably get away without cooling but I'd recommend a small fan anyway. Heatsinks do not work for 5mm LEDs.

Another option is to use high power 8mm LEDs. 1 8mm LED can replace +/- 5 5mm LEDs. You'll end up using less space, but a cooling fan will be necessary.

check this out: http://cgi.ebay.com/High-Power-LEDs...55714QQcategoryZ66952QQtcZphotoQQcmdZViewItem


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## Ken_McE (Feb 18, 2006)

foo_fighter4000 said:


> ...One other thing - if i put these 50 LED's (between 20,000 and 40,000mCd's each) ...



Mcd is a fairly useless measurement. You need their output in lumens.


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## markus_i (Feb 20, 2006)

foo_fighter4000 said:


> So do you reckon its possible to get enough light out of a mixture of red, green and blue LED's yet keeping the total numbers under 50??? I want to keep the unit really as small as poss!
> 
> One other thing - if i put these 50 LED's (between 20,000 and 40,000mCd's each) as well as the power supply/power converter into a small box - say no bigger than 10x10x10cm - would it need cooling? if so would they need a fan or could i get away with a heatsink?
> 
> Thanks again!



Ok, if you have 10x10x10 cm and someone who is good with a (NC) router, you could fit in:
- 12 Lux IIIs, 4 groups of three with triple lenses (you'll have to experiment with the colour distribution though, an equal number of R/G/B is probably not the best way since R and G are much brighter than B), setting the lenses (50 mm dia.) in a 2x2 array, assuming about 40mm height used up
- 2 50mm Fans (or three smaller ones)
- a custom PSU and controller unit
I'd skip on the kettle cord, though - for this application, the connectors are much larger than necessary. In the industrial electronics area there are several smaller and better suited (e.g. locking) 230 VAC connectors.
Box would have to be made from a solid piece of aluminium, 10x10x10 cm. Total light output for white should be comparable to a 50 W halogen (MR-50) reflector bulb, much better for coloured light.

If you can't use the router (I can't), you could either increase the size by a few cm or use single stars with Carclo optics in hex holders on a standard heatsink (with a couple of fans). In this case, with max. density, you could go up to 15 Lux IIIs (row of 5, row of 4, row of 5, row of fans).

Bye
Markus


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## markdi (Feb 20, 2006)

Oh well I had the concept right but the wrong colors


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## hotbeam (Feb 20, 2006)

I'm still not clear, did you want white light or RGB mixture for any coloured light? If white, that is easy, if RGB, do you have a controller in mind? DMX or did you want to have a driver for the R, G and B individually? That would be cheaper but more tedious to change colour.


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## mezzman (Mar 14, 2006)

Not to rain on your parade, but LED lighting for stage has quite a ways to go as far as intensity over distance and color rendition goes. I have used a lot of LED products for stage and TV, and they are only useful for illuminating scenic elements at close range, not for lighting people. The way that narrow bandwith RGB LEDs combine to create colors tends to always look rather unflattering on skin. LEDs are difficult for collimating their output in a lensed fixture, such as the ones used for lighting a stage from overhead. They are best used in a wide pattern wash application. 
I have used Color Kinetics ColorBlast 12 fixtures a lot and they incorporate 12 each of Red, Green and Blue Lux III emitters within an aluminum low profile enclosure that also acts as a heat sink.
Fans in an intimate venue would be distracting, so the quieter, the better.
As control goes, DMX is the defacto standard in most modern venues, I have seen very few analogue 0-10v control systems in current use.

FYI, The power supplies for these units can power 12 fixtures, for a total power consumption of 750 watts and 13.5 Lbs., 18.50”W x 5.22”H x 8.50”D


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## foo_fighter4000 (Apr 15, 2006)

Right well here i am a couple of months later...

i eventually went down the route of LED lighting. ive developed a working prototype of the board using 96 LEDs. ive used Red Green and Blue and with this i can also get CMYK colours too.

ive also managed to get them to run from a sealed lead acid battery (for about 4 hours - plenty of time). My next prototype will include a small wireless transmitter that will link to a laptop or a controller so programs can be worked out!

Ive taken them to pubs and they are plenty bright enough to support a band in a smallish pub.

ive now got to the stage where ive finilised the spec but i now need the views of performing musicians to tell me what would be good and bad about the design of the casing if you were taking it gigging in small venues like pubs.

from the start ive been anticipating just plonking these cubes ontop of bits of PA or tables etc infornt or at the side of the stage but now im wondering if stands are needed? or clamps? ive also looked into the idea of telescopic poles to save space... im not sure if these'd be suitable tho... 

ive uploaded a couple of pics of what it could look like and the working prototype ive built via these links (sorry dont know how to include them on this!)...

board front:
http://img517.imageshack.us/my.php?image=dscf20098jo.jpg

Board back:

http://img136.imageshack.us/img136/1142/dscf20061ok.jpg

Initial idea:

http://img517.imageshack.us/img517/97/stacked3hd.jpg

Poss idea 1:

http://img136.imageshack.us/img136/8130/134ra.jpg

Poss idea 2:

http://img517.imageshack.us/img517/8437/279op.jpg


there are loads more but these are just a few!

any input would be greatly apprieciated! what would be better? i originally loved the idea of say 4 units you could take out of a briefcase and just place around with minimum work as their completely wireless... would a stand be better tho? do you really want the hassle of putting up stands etc? 

Cheers,

James


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## foo_fighter4000 (Apr 18, 2006)

no one? any one? please!?


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