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Discussion Starter #1
Hey guys. I've been searching through the forum for a while now looking for a solution to what seems like a really simple problem, but so far I've not found anything satisfactory. I'm looking at doing a fairly large scale pepper's ghost effect this year in my garage (using shrink window film on a frame to keep it economical.) My goal is for the ghostly figures (a pair of animated skeletons) to be lit with UV that automatically fades in and out slowly. Emphasis on automatically.

The best solution I've come up with so far is UV LEDs, an Arduino, and a PWM board. That solution comes out to about $30-$35, which isn't too bad. However, I have concerns that LEDs, even a few of them grouped together, wont be bright enough given the scale of the effect.

A DMX solution seems overkill, not to mention much more expensive from what I've seen. I want it automatic, so a simple light dimmer box is out of the question. Any other ideas that my searches haven't turned up?
 

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Do you mean black light? True UV isn't visible to humans. Not trying to be a jerk, i just don't want you to buy the wrong LEDs.

I think DMX seems to be overkill too unless you already have the stuff for it.

i'd go the Arduino route but you may want to consider a relay that controls a higher wattage black light.
 

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Discussion Starter #5
I offer a High output LED FADER that has a pot for adjusting the fade up/down rate. It's microprocessor controlled and I can custom write the program if you want it to perform differently than the description. It can output up to 5A.
http://m.ebay.com/itm/LED-Fader-Controller-High-Output-PWM-LED-Fade-In-Fade-Out-Fading-LED-Eyes-/272099204851?nav
That's a nice little circuit. That will definitely be a consideration for me. At 5 amps max I should be able to get a decent number of LEDs on there. So if nothing else, I guess I could go for just a large number of LEDs if it wasn't bright enough. I'm not super fond of the idea of creating my own 30 LED flood by hand though, heh.

Do you mean black light? True UV isn't visible to humans. Not trying to be a jerk, i just don't want you to buy the wrong LEDs.

I think DMX seems to be overkill too unless you already have the stuff for it.

i'd go the Arduino route but you may want to consider a relay that controls a higher wattage black light.
Thanks for the heads up. My understanding is that blacklights and UV lights are pretty much synonymous. UV is invisible until it gets absorbed by something in the correct range, it shifts it, and emits it again into a visible spectrum. Hence the unnatural glowing effect. Correct me if I'm mistaken.

Relays have the issue that J-Man mentioned; I'm looking for a smooth fade-up and fade down. I've done some brief research on how to make an Arduino control a 120v line with fade control, but so far I've not found anything compelling. A pre-made circuit would be ideal, if you know of any.
 

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black light queen
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how about a slowly rotating motor with cardboard attached to the shaft?

you might get the fade effect with holes punched into the cardboard ... the closer the holes the more light, conversely spacing the holes further apart the dimmer it'll be

i haven't tried this, but the idea just came to me

you'll probably have to experiment to get the desired effect

if you try this, let us know how it turned out ... take a video, maybe even make a tutorial

but you better hurry, i'm submitting my patent tomorrow, lol :) j/k

amk
 

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Here is my solution: $10 rotisserie motor w/batteries, washer, bolts, nuts, coat hanger wire, brackets, screws and two sliding dimmers. Hopefully you already have a bunch of these parts lying around like I did. The wire connecting the two dimmers can be removed if you only want one dimmer to fade up and down (depends on the effect you want).

This was for traditional lighting, so it might not work for you unless your LEDs are dimmable. But honestly, I found that regular white bulbs worked best for my Pepper's Ghost (cheaper, stronger light). I think you should seriously consider regular lights.

There are two types of Pepper's Ghost displays: one does a true cross fade, and has matching backgrounds in both chambers, and the other only fades up and down the side chamber, to overlay a reflection on the straight-ahead scene (best dimly lit). With the second type, the trick is to keep the background of the side chamber as (matte) black as possible, so that only the object you wish to reflect is exposed by the light. A black light is better in this regard, but as you probably already know, more costly and much hotter to run. Not sure how cost effective a large array of UV LEDs would be in the end, never having tried them, but my gut says $$$.





 

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black light queen
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i took a look at the ebay link as i am always on the look out for uv leds :D

they say that they're using epistar leds so i had a look at the epistar web site and couldn't find any information on their uv leds ... i specifically am interested in 365nm wavelength and it doesn't appear that they make any leds with a wavelength smaller than 445nm :(

so, i'm extremely skeptical about their claim(s)

365nm leds are still expensive :(

amk
 

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black light queen
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Here is my solution: $10 rotisserie motor w/batteries, washer, bolts, nuts, coat hanger wire, brackets, screws and two sliding dimmers. Hopefully you already have a bunch of these parts lying around like I did. The wire connecting the two dimmers can be removed if you only want one dimmer to fade up and down (depends on the effect you want).

This was for traditional lighting, so it might not work for you unless your LEDs are dimmable. But honestly, I found that regular white bulbs worked best for my Pepper's Ghost (cheaper, stronger light). I think you should seriously consider regular lights.

There are two types of Pepper's Ghost displays: one does a true cross fade, and has matching backgrounds in both chambers, and the other only fades up and down the side chamber, to overlay a reflection on the straight-ahead scene (best dimly lit). With the second type, the trick is to keep the background of the side chamber as (matte) black as possible, so that only the object you wish to reflect is exposed by the light. A black light is better in this regard, but as you probably already know, more costly and much hotter to run. Not sure how cost effective a large array of UV LEDs would be in the end, never having tried them, but my gut says $$$.





luv this!

amk
 

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i took a look at the ebay link as i am always on the look out for uv leds :D

they say that they're using epistar leds so i had a look at the epistar web site and couldn't find any information on their uv leds ... i specifically am interested in 365nm wavelength and it doesn't appear that they make any leds with a wavelength smaller than 445nm :(

so, i'm extremely skeptical about their claim(s)

365nm leds are still expensive :(

amk
They do have 365nm but they're pricey, $36.
http://m.ebay.com/itm/Outdoor-10W-UV-Purple-365-375-385-395-405-415nm-LED-Flood-light-110-220V-12V-DC-/282041018021?nav=SEARCH&varId=580988947050
 

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Discussion Starter #13
how about a slowly rotating motor with cardboard attached to the shaft?
[...]
Thanks for the idea. I had actually considered a mechanical solution, but I'm not a huge fan of the idea. My concern is mainly around reliability and my ability to get the lighting exactly where I need it. Floods and LEDs can be clamped in small spaces to get the exact angle I need, whereas a mechanical solution like that takes up a lot more space. I really like clean electronic solutions (I guess that's my software background coming out.)

What kind of UV LEDs are you getting? I bought a roll of them last year. They are not very bright unless you are close up. The whole roll runs 4.7amps
I was eyeing these on Amazon: http://www.amazon.com/microtivity-IL162-Clear-Violet-Resistors/dp/B004UZ3ZCG

Though, admittedly they're near-UV, not full UV. Supposedly there's enough UV in them to get a glow still. They're cheap enough that I could just buy them and test them I suppose.


Here is my solution: $10 rotisserie motor w/batteries, washer, bolts, nuts, coat hanger wire, brackets, screws and two sliding dimmers. Hopefully you already have a bunch of these parts lying around like I did. The wire connecting the two dimmers can be removed if you only want one dimmer to fade up and down (depends on the effect you want).

This was for traditional lighting, so it might not work for you unless your LEDs are dimmable. But honestly, I found that regular white bulbs worked best for my Pepper's Ghost (cheaper, stronger light). I think you should seriously consider regular lights.

There are two types of Pepper's Ghost displays: one does a true cross fade, and has matching backgrounds in both chambers, and the other only fades up and down the side chamber, to overlay a reflection on the straight-ahead scene (best dimly lit). With the second type, the trick is to keep the background of the side chamber as (matte) black as possible, so that only the object you wish to reflect is exposed by the light. A black light is better in this regard, but as you probably already know, more costly and much hotter to run. Not sure how cost effective a large array of UV LEDs would be in the end, never having tried them, but my gut says $$$.
[...]
Hehe, that dimmer is an epic bit of Halloween engineering. Like I just said, I'd really prefer an electronic solution to keep it simple and reliable.

Hmm, interesting points. I'm planning this as the latter; a fade up and down of the side chamber without any change of the light in the main chamber. I had defaulted to using UV since it looked like that's what the Haunted Mansion was using in their ballroom. I thought this pic from this website made it look like the ghosts are painted for blacklight. Maybe not though, now that I look closer. Anyone know? Maybe I should reevaluate and go with a combination of white and blue LEDs, which should be a lot brighter.


Fascinating. Definitely not cheap (compared to the LEDs I've been looking at anyway.) Thanks for the link; I'll add this to my possible BOM.
 

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Not sure if you've ever used one of those 10W LED floods but you can't compare the amount of light one of them produces to 5mm standard LED's, even 30 of them.
 

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Like I just said, I'd really prefer an electronic solution to keep it simple and reliable.

Hmm, interesting points. I'm planning this as the latter; a fade up and down of the side chamber without any change of the light in the main chamber. I had defaulted to using UV since it looked like that's what the Haunted Mansion was using in their ballroom. I thought this pic from this website made it look like the ghosts are painted for blacklight. Maybe not though, now that I look closer. Anyone know? Maybe I should reevaluate and go with a combination of white and blue LEDs, which should be a lot brighter.
The rotisserie motor worked for several weeks without much break. ;)

Black light is better in general because the black background doesn't bounce it back to the scene at all, whereas strong normal light will tend to leak back. A very matte black helps mitigate that. (Look for ultra matte black with a chalky finish at a craft store like Michael's.)

Thinking about the 10W LED, that is a lot of power and might do very well (as long as the wavelength is right; not sure myself what the wavelength needs to be.) Painting your side props with fluorescent paint is a great idea...good boost in brightness under blacklight. Phosphorescent should work with a wider wavelength gamut if the LEDs you find aren't purely blacklight frequency. The only problem there (or feature) is that phosphorescent tends to keep glowing for a while after it's energized. The fade might be a nice side effect.

In general, be prepared to do a lot of adjustments and tweaking to get it looking the best, with as little leakage as possible. A deeper side chamber can help with that, too.

GOOD LUCK!
 

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I searched for a cross fader(electronic) for quite a few years. Cowalicious made some about 15 years ago but I couldn't afford it then. Think they were around $40. Haven't seen one since, and I was looking. I too needed a solution and made a mechanical fader. I had to have a peppers ghost. This was my version.
http://vid6.photobucket.com/albums/y220/indianaholmes/100_1631.mp4

This was the only video I have of the effect. Its hard to film peppers ghost, but it is one of the most spectacular props you can have.
https://youtu.be/936DOaK8Xrc
 

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Discussion Starter #17
Not sure if you've ever used one of those 10W LED floods but you can't compare the amount of light one of them produces to 5mm standard LED's, even 30 of them.
I have not. If they're that much better I'll definitely consider it. At some point here within the next few months I'm sure I'll construct the effect full-scale, so that will give me a good chance to see how well cheaper options work before springing for the LED flood.

The rotisserie motor worked for several weeks without much break. ;)

Black light is better in general because the black background doesn't bounce it back to the scene at all, whereas strong normal light will tend to leak back. A very matte black helps mitigate that. (Look for ultra matte black with a chalky finish at a craft store like Michael's.)

Thinking about the 10W LED, that is a lot of power and might do very well (as long as the wavelength is right; not sure myself what the wavelength needs to be.) Painting your side props with fluorescent paint is a great idea...good boost in brightness under blacklight. Phosphorescent should work with a wider wavelength gamut if the LEDs you find aren't purely blacklight frequency. The only problem there (or feature) is that phosphorescent tends to keep glowing for a while after it's energized. The fade might be a nice side effect.

In general, be prepared to do a lot of adjustments and tweaking to get it looking the best, with as little leakage as possible. A deeper side chamber can help with that, too.

GOOD LUCK!
Thanks for the tips. I've not tried a pepper's ghost effect before, and as far as I can tell very few people are doing them large-scale, so practical tips like that are super helpful.

Do you think black heavy blankets would work alright? I'm going to have to backdrop a side-room that's at least 6' x 6', and I'm fairly sure I could secure some old comforters and sheets to hang at no cost. If not that, then I'm looking at just super simple black tarps (search "black tarp" on Amazon) but I'm concerned they're going to be too glossy.


I searched for a cross fader(electronic) for quite a few years. Cowalicious made some about 15 years ago but I couldn't afford it then. Think they were around $40. Haven't seen one since, and I was looking. I too needed a solution and made a mechanical fader. I had to have a peppers ghost. This was my version.
http://vid6.photobucket.com/albums/y220/indianaholmes/100_1631.mp4

This was the only video I have of the effect. Its hard to film peppers ghost, but it is one of the most spectacular props you can have.
https://youtu.be/936DOaK8Xrc
When I was posting this thread I was thinking I must be overlooking a solution and that someone would quickly post the obvious off-the-shelf solution. I'm glad it's not just me being challenged by this task, hah.

That's a very well-constructed mechanical cross fader! Really good use of the cheap linear rail sliders. What motor is that running it?
 

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Do you think black heavy blankets would work alright? I'm going to have to backdrop a side-room that's at least 6' x 6', and I'm fairly sure I could secure some old comforters and sheets to hang at no cost. If not that, then I'm looking at just super simple black tarps (search "black tarp" on Amazon) but I'm concerned they're going to be too glossy.
With blacklight I wouldn't have a second thought that black blankets would work. Even regular light would most likely be ok. Your gut seems right about tarps glossiness. You want to avoid any sheen or gloss which can reflect light back, even if it's subtle.

A practical consideration is the set back of the side scene and the viewer from the entire display. You need to keep the view angles such that the viewer can't see into the side scene at all (or as little as practically possible). With a 6x6 room (and a 6x6 main scene), you'll need to keep the viewers back a good ways (12 feet? but the more the better). If the side chamber is on the left, say, the view angle from the far right will still catch more of it. Just plan to set any side chamber props and lighting back as much as possible.

And returning to the LED power issue, more power can actually be a problem if it gives away the side chamber. I found I had to limit brightness on my setup to get the effect I wanted, without giving the side chamber away. I had a much smaller space and was using real glass, which proved a challenge.
 

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Discussion Starter #20
With blacklight I wouldn't have a second thought that black blankets would work. Even regular light would most likely be ok. Your gut seems right about tarps glossiness. You want to avoid any sheen or gloss which can reflect light back, even if it's subtle.

A practical consideration is the set back of the side scene and the viewer from the entire display. You need to keep the view angles such that the viewer can't see into the side scene at all (or as little as practically possible). With a 6x6 room (and a 6x6 main scene), you'll need to keep the viewers back a good ways (12 feet? but the more the better). If the side chamber is on the left, say, the view angle from the far right will still catch more of it. Just plan to set any side chamber props and lighting back as much as possible.

And returning to the LED power issue, more power can actually be a problem if it gives away the side chamber. I found I had to limit brightness on my setup to get the effect I wanted, without giving the side chamber away. I had a much smaller space and was using real glass, which proved a challenge.
I've been toying with the angles a lot in Visio. Here's what I have so far:

perppers_ghost_room_diagram.jpg

The red sight line is the worst angle that a guest could achieve, which still hides the source. The blue line to the center of the mirror measures just under 7'. The green bounced sight line also measures just under 7'. So that will make the ghosts appear to be about 14' back from the guest, give or take a couple feet. That all sound about right?
 
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