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Discussion Starter · #1 ·
Well, guess I need to get started on some type of new prop for this year! We only had 3 TOTs last year, but hoping for more in '21! I kind of have this idea sloshing around in my brain... My take on the 'ghostly footprints' set-up - so here are the key points:

I want to have a set of footprints appear to be 'walking' up the path to our front door. As the walkway is concrete, I can't do the standard plastic panels or other physical lights/leds to make the footprints. Projection might be a possibility, though I'd need a dozen small projectors and the cheapest I seem to see them is about $7.50 each - sold as 'puddle lamps' for car doors. I'd still need to come up with some sort of 'footprint' image to project and I don't think the contrast is too high as these are shining a light through a small film slide.

So thinking of trying to get some 'invisible' fluorescent paint or similar (fabric brightener?) for the footprints on concrete. Then, off to the side of the walk, I am planning to have some 'true' 365nm LED blacklights. One LED for each footprint to make the UV paint glow without casting a visible purple glow themselves. I will try to make some sort of a spotlight hood for each LED, so one LED can be focused on one footprint and there won't be any purple/UV light projected upward. Possibly disguise the LEDs in ??? dead tree branches? Then a quick arduino sketch to fade in / fade out each footprint in sequence to make the 'walking' pattern.

So for right now, have some LEDs on order to see what kind of 'glow' I can get with different substances, a rough outline for an arduino sketch, and a tentative board thrown together so the arduino can switch MOSFETS for the high current LED supply. (I ordered 3Watt, 365nm 'true' blacklight LEDs, so need to switch about 750mA @ 4 volts for each LED)

Looking forward to some LED tests soon!
 

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Definitely sounds like an interesting project to puzzle out.
 

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Could you possibly just have one or two LED blacklights, with a rotating drum with slots in it, and put this higher overhead? (Hope this is clear)
 

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That sounds like a really interesting build. I really like the idea of using a clear reactive substance to illumiate with a blacklight that makes the footprint appear. You may have a little bit of an afterglow to deal with depending on what you use though. As far as hiding the lights that is going to be pretty tough depending on what you have to work with. It would be a great illusion to pull off. I am looking forward to see what you come up with.
 

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There was a big discussion of this illusion many years ago. What worked best was footprints of acrylic with leds inserted in the edge. The surface of the prints was sanded to a frosted finish to capture the light. Someone even programmed an Arduino to provide the correct sequence. I believe the original was on Halloween.com and included a ghostly tricycle that started pedling when the steps arrived.
 
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Definitely sounds like an interesting project to puzzle out.
Do you remember the glowing footprints that walked from a tricycle to a tombstone. It was done with acrylic cut outs and a sequencer. It was even a $20.00 prop challenge entry.
 

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Do you remember the glowing footprints that walked from a tricycle to a tombstone. It was done with acrylic cut outs and a sequencer. It was even a $20.00 prop challenge entry.
This might be what you’re thinking of:


 

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Here’s another thread that discusses the effect.

 

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Discussion Starter · #9 ·
@ Dave Leppo - Interesting thought - I see what you're getting at. There is only open sky/open space around the path, so I'd almost have to make some sort of gateway or arch to hold anything 'up' - though in a different setting...indoors or some sort of overhead roof already existing, I could see how that might be very effective. I may puzzle over this a bit more, though!! Thanks!

All others - thanks for the additional input. I do remember seeing some acrylic footprints - that is sort of what got me started thinking along these lines - the only issue is that this is a concrete walkway that people will be walking on - so no real way to put acrylic pads out there - they would trip over the bumps and wires. Plus, even if I built some sort of platform to hide the acrylic, I think in this case it would just look like 'lights in the floor'. I'm hoping that with these 'true' blacklight LEDs, I can get a notable glow out of the 'essentially invisible' footprints, with no apparent lighting or purple glow. We will see!

The path I'm working with is probably best shown in the opening moments of my 2009 video.

So to get started...faster than you can say "Bloody Mary" three times infront of a mirror, the LEDs are here! Actual shipping time was about a week, so not bad!


Want to run couple tests right off the bat... what do the LEDs look like in the dark?

LED shining on a non-UV active surface....well, darn! This might be a show stopper right off the bat. Even though these are "365nm" LEDs and can easily throw out light +/-20nm of that, they still throw out a ton of visible light! I was really hoping the effect would be that of something 'magically' glowing on the ground, not CSI running around with the blue-purple flashlights! I should also add that this is pretty much what you see in real life - it's not some trick where the camera picks up much more light than your eye can see.



Next test - do my LED lenses still work in the UV range? Have several of these on hand from a project long ago - I believe they are supposed to make a 20degree cone. Stick one on a visible LED and yes, it projects a nice cone of light. Good - the plastic is not blocking too much UV, or at least the focusing power of the lens makes up for any drop in output.



So now what to do?!?! I think the light coming out of these 'true' 365nm blacklight LEDs is even more visible and obtrusive than the light coming out of some of my 'not true' 405nm fluorescent blacklights. I guess I could try to get some 365nm bandpass filters on order, that might help cut some of the visible glow. What is another 8 bucks! So back into a holding pattern waiting on more parts!
 

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Now I'm thinking it might be better having sets of lights lower to the ground, like a foot or two above the path surface, off to the side, with a shade or shield above each, so that you cant see the light source when standing next to it. one per footprint, and sequenced with a controller.

The really fancy version: Invisible IR sensor beams at each set make the next set come on, so when someone is walking up the path, the footprints directly in front of them light up. If they stop, the ghost walking in front stops, too. If they go faster, the ghost goes faster.
 

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Discussion Starter · #11 ·
That is the effect I was hoping for... 10 (at least for now) LEDs, with a lens / hood to focus the light in a small patch to light up one footstep each, and let an arduino run the 'steps'. Though the way it would look right now would be 10 flashlight beams hitting the ground! I was led to believe that 365nm blacklight was 'true' in that you wouldn't see a purple glow at all. Meaning the steps would almost look to be magically glowing. But definitely not what I see now as the pics show! Hopefully the filters can solve that, but will have to wait and see!

I like your idea about the ir sensor beams! Hadn't thought of that! Hummm...maybe I should get some PIR sensors on order too.

(You realize this 'hey wouldn't it be cool if...' ideas are why my plasmaduino was a 17 year project!?!? lol :))
 

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Discussion Starter · #13 ·
Thanks for all the additional input! I've done some additional 'designing' but haven't done much physical - pending the arrival of my UV notch filters to see if I can block out the hideous amount of visible light coming out of these LEDs. Well, the filters arrived last night!

Only had a moment to give the set-up a quick try and in one word....disappointing!

Still have a bunch of visible purple glow coming out of the LED. Admittedly, its a much darker purple now, but at best, you'd see a glowing footprint in a purple circle of light shining on the ground. Still not the effect I was hoping for. I'll try to get some updated photos, maybe try a bit lower power on the LED, or two filters stacked for additional visible light blocking.
 
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