jexjexjex Posted March 21, 2012 Share Posted March 21, 2012 Had a trawl through the Spotlight website and found this. Interesting to note that it comes in two versions, one of which simply plugs into a standard dimmer in the good old "one light - one channel" fashion. Almost traditional, you might say? Given that there are a lot of venues out there with a lot of new conventional dimmers, is this not the way to go? A venue could "go green" with no additional DMX requirements but still retain flexibility, if the need was there to bring in a load of PAR64s! Link to comment Share on other sites More sharing options...
Ynot Posted March 21, 2012 Share Posted March 21, 2012 Had a trawl through the Spotlight website and found this. Interesting to note that it comes in two versions, one of which simply plugs into a standard dimmer in the good old "one light - one channel" fashion.Hmmm...I'm struggling to see how they can do that... Link to comment Share on other sites More sharing options...
ramdram Posted March 21, 2012 Share Posted March 21, 2012 Intrigued so had a look for 100W LED chips: http://www.adflyer.co.uk/home-and-garden/home-general/lighting/light-fittings/high-power-3500ma-100w-led-board-7000lm-32-36v-110/1463730 seem to be a few knocking about and some even higher ratings. Now, presuming I have grasped the concept correctly these lanterns must be equipped with something similar, on the grounds that the lantern has barn doors, which implies, to me, a point source. Corrections welcome of course. Presuming even further, and, taking into account the lantern casing looking decidedly "dated", do you suppose the manufacturer has cobbled one of these LED units into an "old" casing and used the existing optical system to emulate a conventional lantern? Perhaps we should recall too that not all LEDs are packaged as the "usual" hemispherical types and consider the types found in a Lenser type torch. If anyone is familiar with Lenser kit then you know the output from "the" chip they use is astonishing. (I have a P2 which has an adjustable lens to give a very sharp spot of intense white light, well, from an AAA cell anyway.) If you had £35 going spare you could buy one of the 100W LEDs and cobble up a Cantata body or similar and see if the beam could be focussed by the original optics. Now there's a thought...just got to think about controlling a suitable dimming device...don't want the snap off and snap on effect...or a stepped dimming curve. Link to comment Share on other sites More sharing options...
kitlane Posted March 22, 2012 Share Posted March 22, 2012 Intrigued so had a look for 100W LED chips: http://www.adflyer.c...36v-110/1463730 seem to be a few knocking about and some even higher ratings. Now, presuming I have grasped the concept correctly these lanterns must be equipped with something similar, on the grounds that the lantern has barn doors, which implies, to me, a point source. Corrections welcome of course. Presuming even further, and, taking into account the lantern casing looking decidedly "dated", do you suppose the manufacturer has cobbled one of these LED units into an "old" casing and used the existing optical system to emulate a conventional lantern? Perhaps we should recall too that not all LEDs are packaged as the "usual" hemispherical types and consider the types found in a Lenser type torch. If anyone is familiar with Lenser kit then you know the output from "the" chip they use is astonishing. (I have a P2 which has an adjustable lens to give a very sharp spot of intense white light, well, from an AAA cell anyway.) If you had £35 going spare you could buy one of the 100W LEDs and cobble up a Cantata body or similar and see if the beam could be focussed by the original optics. Now there's a thought...just got to think about controlling a suitable dimming device...don't want the snap off and snap on effect...or a stepped dimming curve. One of my students did something similar to this a couple of years ago. I was initially pessimistic but the results were pretty good. Remember that a normal Cantata (for example) doesn't really have a true point source; the filament is a few millimetres long. Link to comment Share on other sites More sharing options...
Tomo Posted March 22, 2012 Share Posted March 22, 2012 Given that there are a lot of venues out there with a lot of new conventional dimmers, is this not the way to go?Indeed, it's not the way to go because 2-wire dimming of LED (like all 'special' loads) remains poor with a big jump at the bottom. In some situations that's fine but in theatre it usually isn't. There is a reason why all the good LED (and florry) fixtures are DMX-controlled. As with all of these, check the literature.The good fixtures will give a lot of information, while the mediocre and poor ones won't. Read page 3 of the Source Four LED datasheet and then Google "B50 L70". That's how a fixture manufacturer can estimate LED lifetime - the same way one can estimate the lifetime of any silicon. Link to comment Share on other sites More sharing options...
ramdram Posted March 22, 2012 Share Posted March 22, 2012 As you remark Kitlane true point sources are perhaps not that common but obviously for the sake of argument I could live with a few mil. So how did your student get on with the dimming curve and the snap on/off issue? Any photos perhaps? Link to comment Share on other sites More sharing options...
gyro_gearloose Posted March 22, 2012 Share Posted March 22, 2012 Smooth dimming is a simple problem that has already been solved, though solving it requires a little lateral thought. The obvious answer to smooth dimming of LEDs is to copy what people have been doing with discharge sources for years - use a mechanical dimmer. For my Miniscan LED conversion I used the in-built dimming rather than try to integrate my own PWM dimming. Dimming is obviously as smooth as the original HMI lamped Miniscan. As for needing a point source, have you looked at the size of the filament of a T19 lamp? Its quite a bit bigger than a few millimetres, and yet in the ADB DS profiles we've got at work it can produce very sharp gobo projection - much sharper than our similarly lamped Cantata profiles, anyway. This is down to the extra lenses placed right next to the lamp. These are often called condensing optics, but the system actually goes by the name of Koehler illumination, and was originally developed to create even illumination in microscopes. Link to comment Share on other sites More sharing options...
timsabre Posted March 22, 2012 Share Posted March 22, 2012 Using a shutter is very wasteful of energy though. It is possible to dim an LED smoothly if you have fixed incoming power and a control signal like DMX. The problem comes with mains lamp retrofits when you are trying to dim the power to the LED with a triac dimmer and hoping for the LED to follow smoothly. That doesn't work. Link to comment Share on other sites More sharing options...
musht Posted March 22, 2012 Share Posted March 22, 2012 Philips and ETC will go head to head for the profile market now. Not entirely, the LED S4 has 60 Philips Lumiled Rebel LEDs... Link to comment Share on other sites More sharing options...
timsabre Posted March 23, 2012 Share Posted March 23, 2012 Philips and ETC will go head to head for the profile market now. Not entirely, the LED S4 has 60 Philips Lumiled Rebel LEDs... It'll be interesting to see how that goes forward, as Philips are no longer selling the top-bin Rebels (i.e. the highest output ones), but instead are building them into their own luminaires. Link to comment Share on other sites More sharing options...
kitlane Posted March 23, 2012 Share Posted March 23, 2012 As you remark Kitlane true point sources are perhaps not that common but obviously for the sake of argument I could live with a few mil. So how did your student get on with the dimming curve and the snap on/off issue? Any photos perhaps? No photos I'm afraid and I'm not sure they would tell you much if I had any. The bottom end of the dimming curve wasn't too good as you might imagine. We did discuss how a mechanical dimming method might be integrated, maybe just for the final few percent which otherwise might fall off a cliff. The starting point for the project was specifically to look at producing a followspot so a mechanical solution wouldn't be too difficult anyway. The brightness of the prototype wasn't sufficient but it looked like the design could be scaled up fairly easily. If we'd had some of the high brightness LEDs available today then I think it would have been quite impressive. Had a trawl through the Spotlight website and found this. Interesting to note that it comes in two versions, one of which simply plugs into a standard dimmer in the good old "one light - one channel" fashion.Hmmm...I'm struggling to see how they can do that... Again, one of my students tried this a couple of years ago. It's feasible but the conversion of the dimmed power into something that would constantly drive the electronics and power the LEDs started to get a bit scary (I bow to the superior electrical engineering knowledge of the 5 PhDs I share an office with!) Imagine that you have a minimum limit on the dimmer channel; maybe a specific dimmer law. So you are always sending some power to the unit to power the electronics and the minimum needed for the LEDs to work. As the dimmed power varies throughout it's now slightly smaller range you measure the level and use that to control the LED dimming. Link to comment Share on other sites More sharing options...
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