pulsar chroma

[computer]

hi,

 

I was just wondering if anyone had any more information than whats on pulsar's site about the chroma range.

 

I understand they're made from lots of high intensity red, green and blue leds, rather than RGB leds. does this mean I could easily and cheaply make my own version (not the banks, just single lights) cheaply, if I use a microchip to control them?

 

thanks,

computer

[Pete McCrea]

Try BigClives website for ideas.

[PH_Zone]

Hi,

Have a look at this web site.

it is in german so will need traslating. http://www.he-privat.de/HV/Pic.htm

 

To make Led ligting is quite simple in the hardware.

But to get enough light output requires the use of quite expensive LED's

 

Paul

[TomLyall]

Translated Version

 

Tom

[computer]

lmao, that translation is soo hard to read :P

 

anyone know how many lumens a chroma fixture puts out?

 

I want to make some decorative lights anyway not really powerful ones, so anything with similar output to a small halogen lamp or something?

[Tomo]

Best bet would be looking through some electronics catalogues and checking out the specs.

 

Red and Green hyperbright LEDs are easily available

- Individual 5mm unit light output is somewhere in the region of 2 to 10 cd. These are cheap though - around 20-40p each.

 

Blue are still pretty expensive - around £1 each - and are less bright (90mcd is the best I've noticed).

 

So to get a bright light you need rather a lot!

 

Farnell are okay (and pretty cheap for large quantities of stuff), but RS have a better online catalogue - more expensive though.

 

You can get tricolour Red/Green LEDs, but I don't think you can get 6-colour RGB LEDs.

 

To 'dim' an LED you have to reduce the current flowing through it, but because they are non-linear devices you can't just ramp the voltage (well, you can but the working range is very small) so you must 'chop' the drive current very rapidly, varying the ratio of 'on' time to 'off' time to get a smooth dimming profile - pulse width modulation.

 

Lightnix is probably your best bet for info on LED tech in general - there's some interesting stuff on his site www.wavicle.biz

[computer]

yea I get the thing about PWM... I have a microchip controller to PWM the 3 outputs for red/green/blue via control from 3 analogue inputs.

 

don't understand what you mean by a 6 colour RGB led? a rbg led is red/green/blue in one isn't it (and you can mix the colours by varying the intensity)

[P. Funk]

6 colours = red, green, blue, cyan, magenta, yellow.

[computer]

oh right, but you can get CMY by mixing the RGB no?

[Guest lightnix]

Lightnix is probably your best bet for info on LED tech in general...

You're too kind and I have to admit that I only sell the stuff rather than design it at the moment. In fact, my entire knowledge of electronics can probably be written on the back of a postage stamp :P

 

As Little DJ mentioned, the project on Big Clive's site sounds like the kind of thing you are after, if you just need to do short throw domestic stuff and will work out cheaper; although the German project would be much better for show work. Gotta love that translation, BTW - it's a bit "literal", although I could probably do a "real" English version for you, given an afternoon.

 

It looks like the German guy is using Luxeon LEDs, which are horribly expensive. A blue 5 watter from Farnell will cost you nearly £23 (+VAT and delivery), with the red and green weighing in at the best part of a tenner each, so that's nearly £40 for the "bulbs" alone, before you get around to using any electronics. When you bear that in mind, £250 for a single Chromaplonk thingy is pretty good value.

 

RGB LEDs are fun to play with, but no use for serious applications IMHO. To start with the blue chip never outputs enough light to achieve proper white and the positioning of the chips within the resin means that you get three separately-focussed spots of light, rather than a single one.

 

Luxeon LEDs have a 140° beam by default and are usually focussed (as with Pulsar kit) to narrower widths using little plastic lenses, which cost about about a fiver each . Do a search in Farnell for "Fraen" (the manufacturers) for a selection. Although LEDs are "low heat" devices, you will need to take heatsinking (and possibly ventilation) into account when using any kind of Luxeon, especially in arrays. Even the 1 watt stars can benefit from having their built-in heatsink beefed up with a penny or two for long term ab/use.

 

You can dim LEDs with a current limiting device, but the best way is to use Pulse Width Modulation, as you already know.

...but you can get CMY by mixing the RGB...

Yes. CMY is really RGB "in reverse". To prove this, take a CMY wash light and turn all the filters into full to give "colour black". Use some PVC tape to rename the colour wheels, so that Cyan is renamed Red, Magenta is renamed Green and Yellow is renamed Blue and have a play with them. What you are now doing is additive (RGB) rather than subtractive (CMY) mixing, where the "end colour" is white, not black.

 

Confused ? You won't be for long once you try it :(

 

Now if you want to see LED technology with the potential to really rock, have a look at Lamina Ceramics :blink: At US$35.31 (+VAT, import duty and shipping), the RGB version of their BL2000 unit is quite a good deal. I've read some great early reports about these little babies and I think we'll be seeing quite a bit of them in the future.

[Tomo]

oh right, but you can get CMY by mixing the RGB no?

Yes, but what I meant was a three-chip LED where you have individual control over the colours.

 

There's two kinds of bi-colour LED - straight bi-colour with two pins so you can light either internal chip, but not both at the same time, and tricolour with three pins so you can light either one or both at the same time to give a third colour.

 

I've since found that you can get 3-chip RGB LEDs, but the light output is lower and they cost more than getting the colours seperately. Not good.