Shroud, Gobos, and Diffuser for Gemmy spotlights

Background

Over the years I have obtained a number of Gemmy Industries' seasonal indoor/outdoor LED spotlights for use in my yard haunt.  You can sometimes find these sold alongside the Halloween and Christmas holiday decorations in big chain stores (such as Lowe's, Home Depot, Kroger, Walmart) and even on Amazon.  They are often sold under Gemmy's Lightshow branding, but are sometimes rebranded; e.g. I believe Home Depot sold them under their Home Accents brand a few years ago.

There are static as well as animated (“fire and ice”) versions of the Gemmy spotlight.

The static lamp style that I have is shown on the left.  Three LEDs of a given color are set into individual reflectors beneath a clear plastic face plate with a recessed circle.  The casing and mounting bracket are completely black.

The animated “fire and ice” style lamp that I have is shown on the right.  It has a faceted hemisphere that covers the LEDs, with a motor inside that provides rotation to create an abstract, multicolored shimmer.  The mounting bracket and face plate are made of grey metal on these lamps.  

Note: I put some paint on each lamp to indicate its color, on the sides or more often the bottom of the bracket, as you can see on the leftmost lamp.  For the fire and ice style, I paint a stripe for each of the LED colors used in the lamp (e.g. yellow and green).

The Issues to be Solved

While I like these lamps, I have a few minor pet peeves when using them in my Halloween display…

1. In a yard haunt, their location can be fairly obvious unless you make an effort to hide them or draw attention away from them.
2. The lighting produced (especially by the static lamps) is very – for lack of a better word – unnatural, and not in the fun, spooky way.  There isn't much variation in brightness/color, and it has an obvious “artificial lighting” pattern to it.
3. They are almost too bright, potentially causing “hot” highlights on props if the light is too close.
4. The glare is exacerbated by the wide throw angle; they can dazzle from fairly far off center, especially the static lamps … which is problematic when you use several around the yard.    This wide angle also makes it difficult to position the lamp such that it illuminates a prop (e.g. tombstones) without spilling out to illuminate the ground, other objects, or the house behind the desired subject.

Shrouding

The first purpose of this printable is to shroud the lamps.  This helps with problem 1 (and to a small degree, problem 4) by reducing their visibility from the rear and the sides. It also helps keep some of the beam off of the grass itself, which otherwise draws attention directly back to the position of the lamp (avoiding this would be considerably easier if the lamp were mounted off the ground, however).

Gobos

The second purpose is to allow me to attach parts to my lamps that block portions of the beam for various reasons.  These parts are known as gobos, and are found in the “Gobos” folder.  A few of the designs I use are shown below.  The tabs in the corners were originally for mounting hardware that is no longer necessary; they've been left in simply make it easier to remove the gobo.

Some gobos – like the one on the left – are merely used to control the overall shape of the beam (making it tall but narrow to match a tombstone, or making it wide but short to illuminate several props, for example).  

The other two designs shown are a type of gobo known as a “cutter”, “cucoloris”, or “cookie", and are used to create a pattern of light and shadow.  This can help make the lighting feel less (or more!) artificial, or can suggest other features of the environment (tree branches, for example).  I mainly use them to create subtle variations in the brightness; they are too far from the subjects to create really sharp shadows.

Diffusion

A diffuser can also help with issues 2 through 4.  That's the third purpose of this printable – to hold a paper diffuser in place on my static lamps.  I typically trace the outline of the lamp's face plate onto a piece of wax paper or parchment paper, cut it out, and put it between the business end of the lamp and the printable.

Pro-tip: If you happen to have white-colored lamps, you can use the same idea with lighting gels or some other transparent colored plastic, such as the cover of a plastic document folder.

If you don't wish to use paper diffusers, I've included files for optional printed diffusers that can fit into the circular recess on the static lamps.  

Neither type of diffuser really works with the animated lamps, of course – they lack the recess for the printed diffusers, while the faceted globe interferes with the paper diffusers.  I suppose I could make a gobo type of part that holds a paper or printed diffuser, but so far I've seen no need; diffusing the shimmering pattern seems counter-productive.

Included Parts

Shroud.stl is the main model for this printable, and it simply press-fits over the end of either style of lamp.

The tightness of the part can vary according to your printer.  If you find that the shroud is too tight, try scaling the model up to 101% or so in your slicer before printing (you would probably also want to scale your gobos to match).  On the other hand, if the shroud is too loose, you can shim it or try scaling in the opposite direction.

The files in the “Gobos” folder are the second sort of model included.  Each one has a different design.  Use whichever you like best; they just press fit into the end of Shroud.stl.

The files in the "Diffusers" folder are the third set.  There are several versions here … the number in the filename refers to the thickness of the diffuser's faceplate in millimeters, so larger numbers mean thicker plastic, which means less light transmission.  You should set your slicer to a layer height that is a multiple of your chosen thickness for best results.  You may also wish to set your top and bottom fill patterns to "circular".  Note that the diffuser models also have little holes on the side so you can distinguish them later (1 to 5 holes, the more there are, the thicker the diffuser is).  If the diffuser is too tight or too loose and you wish to scale it, do so along the X and Y axes, but not Z (height).

Compatibility

The shroud is only compatible with lamps that share the same face plate shape and size as those shown in the photo above.  For example, there are Gemmy lamps that have a more circular outline, as well as multicolored lamps that have a large partial globe attached that is wider than the face plate, and the shroud doesn't work with those. 

Gemmy also makes lamps that project moving images of snowflakes or ghosts or whatever.  Some of these have approximately the same external case design as the static lamps I have.  While it is technically possible to use my Printable with this projector variant (as far as I know), I don't own any of these to test with.  Other than shrouding the lamp I am not really sure why you would want to do it.  The projector lamps need to project clear and distinct shapes, so diffusers and gobos sort of work at cross-purposes.  In any case, you can try it if you want to.

Printing

The parts can be printed with whatever settings work best for you, but here are my suggestions.

Print the Shroud and Gobos with a black or dark colored filament if you have it; lighter colored filaments mean the part will be more prone to light leakage/glowing unless you paint them, inside and out.  (I recommend several coats of matte black.)  

You might think that more infill equals less chance for a light-colored part to glow, but in practice, you can't really affect it much that way and some regions are already effectively printed solid, so more perimeters are also of limited use.

You can additionally paint the interior barrel silver, or line it with foil tape or aluminum foil if you want to prevent the light from getting “soaked up” by the dark surface.  I'll note that, sometimes, letting the light get soaked up is exactly what you want; one thing these lamps have in abundance is brightness.

PETG, ABS, or similar filaments are preferred for their temperature resistance – not because the lamps get hot, but because they are left outdoors.  You may be able to get away with PLA, depending on climate and amount of sunlight the parts will be exposed to.

You would normally print the diffuser in a natural or white filament, but printing with a transparent PETG could also be useful.  There are several versions of the diffuser file … the number in the filename refers to the thickness of the diffuser's face in millimeters, so larger numbers mean less light transmission.  Note that the diffusers also have little holes on the side so you can distinguish them later (1 to 5 holes, the more there are, the thicker the diffuser is).  For best results, you should set your slicer to a layer height that adds up evenly to your chosen thickness.  You may also wish to set your top and bottom fill patterns to "circular".

Usage

This image shows the Shroud.stl with a printed diffuser and a detached chevron gobo.

The image below shows an older version of the shroud in use with a static lamp and the chevron gobo.  Note that the shroud is leaking light in the middle, as it needs another coat of paint.  That wasn't a huge priority, since it was somewhat hidden behind a tombstone.

The photo below shows an animated lamp with an older version of the shroud and no Gobo (as it's merely being used to cut the light spillage immediately around the lamp).

The two images below show the result of using the middle Gobo design shown earlier (shining onto a white door to show the pattern).  The first image shows the result when the lamp is fairly close to the door.  Notice how blown out the highlight in the center is.  The second pic shows the pattern when the lamp is moved further away from the door, and is typically what I aim for when placing them.