Magic lantern project

[Peter]

For an art installation: Two lanterns will project slightly different image s from glass slides onto the same screen. One should fade up as, or after, the other fades down. The difficult bit is that this needs to happen automa tically every few minutes, as the installation is to stand unattended as pa rt of a gallery display.

When the lanterns were built they would have been lit by oil or gas; the pl an is to use GU10 leds of about 5W 27deg beam behind each slide. Although l ow wattage dimmers are sold for these I cannot find anything which would do the job automatically. I have seen a string of fairy leds which fade up an d down on their own though...

Any ideas where to look?

[Martin Brown]

It would be some fairly simple control electronics to do this - basically PWM so that one LED is on and the other is off.

Then set it up so that after a period one fades up as the other fades down. For a pair with fade in/out you can have just one bipolar driven output with one LED connected to +V and the other to OV.

Asking in one of the electronics groups will get you pointers to a suitable circuit. BTW are you sure you don't want to use batwing bare LEDs of about 5W - they are a much better approximation to a point source than a GU10 (need heatsinking to stay alive though).

[Peter Parry]

Ideal project for an Arduino so possibly your local school might use it as a class project or do you have any hackerspaces (hackspaces) or Makers near you?

[meow2222]

ges from glass slides onto the same screen. One should fade up as, or after , the other fades down. The difficult bit is that this needs to happen auto matically every few minutes, as the installation is to stand unattended as part of a gallery display.

plan is to use GU10 leds of about 5W 27deg beam behind each slide. Although low wattage dimmers are sold for these I cannot find anything which would do the job automatically. I have seen a string of fairy leds which fade up and down on their own though...

Many possible solutions exist. None are ready made afaik, so it'll take tim e & money.

NT

[spuorgelgoog]

A small lighting controller with a programmed repeating fade - try the lighting forum at

Owain

[Peter]

ges from glass slides onto the same screen. One should fade up as, or after , the other fades down. The difficult bit is that this needs to happen auto matically every few minutes, as the installation is to stand unattended as part of a gallery display.

plan is to use GU10 leds of about 5W 27deg beam behind each slide. Although low wattage dimmers are sold for these I cannot find anything which would do the job automatically. I have seen a string of fairy leds which fade up and down on their own though...

Thanks for all ideas. I am out of my depth with electronics but following P eter's suggestion found a Build/Hacker group just around the corner from me ! - had never heard of them. Hoping for an interested maker..

[Roger Mills]

Have you considered a mechanical solution rather than an electronic one?

Something like a frosted glass plate of varying opacity which is moved between lamp and slide, perhaps. Could either slide up and down or rotate - depending on shape and layout.

[Andrew Gabriel]

Back in the days of slide projector presenations, 2-projector cross-fading was a standard practice, with alternate slides loaded into each projector's carrossel, to give no break between slides. Slide change always took place in the dark whilst the other projector was showing its image. It was particularly good for build-up slides, but in any case looked more professional than single projector slide changes.

[Brian Gaff]

Sound to light displays? Discos used to have this effect where one colour faded to another a lot. Brian

[Brian Gaff]

Ah, memories. I can remember at school, a clever magic lantern slide, presumably with its levers made out of a transparent substance, ehre if you cranked a handle a horse appeared to gallop .

Of course when cine arrived all of this stuff was killed off. The light in the one we saw seemed to have had some kind of fuel, but it smelt terrible. I bet health and safety would not allow it near a school today!

Brian

[Gazz]

yup, the only foul smelling things found in schools nowadays (apart from the feral kids) comes from the bogs where the pupils are smoking squidgy black.

[Nightjar]

It would be more in keeping with the lanterns.

Colin Bignell

[Roger Mills]

Indeed.