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led channel requirements

The Boogie Man

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Hi Troops, Just a quickie (ooh err)


I'm getting some led par 56 cans and wondered about minimum channel requirements.

The set up is going to be 4 cans per side pointing down at me, 2 on the floor pointing up at me and 2 white cans to act as a sort of between song stage wash/spot. 12 cans in all.

The cans need 5 channels each so would a 48 channel desk suffice?

I know that the two sides could be linked as mirror image, but I like the idea of being able to control each light.


Also would a yellow gel over a white led can give a better yellow than mixing would on an led?



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OK 12 lamps at 5 channels means you need 60 channels. So if you start some lamps in pairs or groups starting at the same DMX channel then the lamps will perform the same and you will save 5 channels. So to come within 48 chan you would need to pair up 3 pairs or more.


If you are using a controller from the lower disco range with several pages of 8 faders then trying to use 5 chan devices other than one per page is challenging, so you could need to pair all the lamps.

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To be honest, if your are going to put a gel on it anyway, just buy a real par!


Gel reduces the light output, which from and LED isnt that great anyway.


And by the way, you won't get a very good white out of LED pars.

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If you use a desk with softpatch you could ignore the function channels, and just patch the RGB. Or pair all the function channels, leaving the RGB separate.
This is definitely a good way to go.

We have 14 6-ch LED cans, and I've driven 12 of them in groups from our 12/24 Strand 200.

I grouped 3 pairs of cans soft-patching their RGB channels to channels 1 thru 9 on the desk, then patched all of their 'effects' channels together on 10 thru 12.

The same with the other 3 pairs on 13 to 21 and effects on 22 to 24.

That gives you semi-individual control of the colours, but still gives you the ability to run two different effects.


As for the yellow gel idea, the only gel I'd consdier over a LED can would be a soft frost to give you a bit more of a mix, though this isn't ideal, as any transluscence will, as stated, reduce the already low output.

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I wouldn't rule out the yellow gel idea to try and avoid the horrible red/green combo which is especially bad on these basic units, but output will certainly be poor. Frost does do wonders. Both yellow and white are the main problem areas - for white on these units you will probably find yourself reducing the red channel a huge amount along with some blue - 100% on all gives lavender.
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Hi guys, first off whoops on the basic maths. I was thinking about how many cans and where I can put them and forgot I'd added a couple. So yes it should be 60 not 48.

Apologies then for sending everyone off on a quest to getting 60 channels into 48 ;)


I see the thinking with grouping the colours and the effects, but I'd really like to keep the ability to control each light. ( I like the idea of not just being able to "crescendo" all the grouped lights, but being able to build up the scene light by light)


On the point about why put a gel on a led, just use a par can: the primary reason for use of leds in my set up is power consumption in small venues not brightness. In use the leds will usually be only a metre ( if that ) above me. In a totally blackened stage area.


On the subject of brightness, as I'm using them this close to me and for the above reasons, does anyone make an led can that is just one colour?

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Ahah, now were talking.


Do I take it that these are like a traditional par can and only have one channel? I can't see from the pic.


The only downside I can see is that one or even two of these for say yellow or white on each side might struggle against the red or blue or green which would be the 51 leds of 8 other cans.


I'll have a look again on the site, but I wonder if anyone does a par can with 150+ same colour leds?

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Those are simple bulb replacements - will fit anything with that size screw fitting. They will not be dimmable. I would have doubts as to them being of usable power.


Many manufacturers certainly do "all white LED" options, not sure about the PAR types.

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Would a yellow gel over a white led can give a better yellow than mixing would on an led?

'Better' is subjective but I would have said no.

The LEDs produce three very narrow bands of light, Red, Green and Blue.

From computers we are very used to mixing these colours to get "all the colours of the rainbow" (don't worry about Indigo and Violet, no-one else seems to).

A Yellow Gel will absorb almost all the Blue light and some of the Green and Red.

The same effect could be achieved by turning the Blue LEDs off and dimming the Green and Red.

The yellow Gel will not change the frequency of the Green or Red light to Yellow.


There will be some small aesthetic affect achieved by softening the light (and avoiding having lots of green and red source dots visible) but this can be better achieved with less loss of light by using diffusion (as others have suggested).


LED cans are relatively cheap, as are LEDs if you really wanted you could swap all the Blue LEDs in a can for yellow LEDs and have yourself a RBY LED-can. (But you'd better like soldering and remember to compensate for the difference in voltage drop between Blue and Yellow LEDs (increase the value of the dropper resistor)).


I've done some comparison between RGB and RGYB LED sources and unless you are illuminating yellow or off yellow (orange -> olive) surfaces it's difficult to spot the difference, even with yellow or off-yellow surfaces the difference is slight. The benefits of diffusion are vastly more noticeable.

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