The New Hotness

Our house came with several single-LED night lights featuring a transparent light guide / reflector:

Nightlight light guide - original — Nightlight light guide – original

The plate had snapped off one of them and, being me, I wondered if I could replace it with something similar.

Years passed.

Obviously, this must be made from a transparent substance, which 3D printed things are not, but after some fiddling with parameters I thought the result might be informative.

The guide plate is a section of a spherical surface, here approximated by a BOSL2 spheroid():

Nightlight light guide - view side - solid model — Nightlight light guide – view side – solid model

The original is 3 mm thick, but 2 mm worked out better for my purposes by reducing the amount of infill:

Nightlight light guide - wall side - solid model — Nightlight light guide – wall side – solid model

The intricate base latches into the lamp’s plastic case:

Nightlight light guide - base - solid model — Nightlight light guide – base – solid model

The result is, at best, translucent, because it’s definitely not transparent:

Nightlight light guide - translucent vs transparent — Nightlight light guide – translucent vs transparent

The zigzag pattern seems to come from the icosohedral approximation to the sphere, because it follows the surface tesselation.

Getting the base shape right required several iterations, each printed with the model cut off just above the bottom of the guide plate:

Nightlight light guide - test pieces — Nightlight light guide – test pieces

The first two attempts needed attention from a flush cutting pliers before fitting into the case, but they don’t call it rapid prototyping for nothin’.

The original and replacement plugged into an outlet strip:

Nightlight light guide - original vs printed on outlet strip — Nightlight light guide – original vs printed on outlet strip

While you can see the vague outline of the strip behind the printed light guide, it’s definitely lacking in detail:

Nightlight light guide - outlet strip detail — Nightlight light guide – outlet strip detail

The striations throw more light into the room than the original:

Nightlight light guide - printed — Nightlight light guide – printed

Fiddling with the 3D printing parameters might make it more transparent, but it’s going back into the box it came from after giving me a better idea of which parameters to tweak the next time around.

The OpenSCAD source code as a GitHub Gist:

	// Nightlight light guide
	// Ed Nisley – KE4ZNU
	// 2026-01-13

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Plate,Base,Pipe]

	/* [Hidden] */

	HoleWindage = 0.2;
	Protrusion = 0.1;
	NumSides = 1034;

	$fn=NumSides;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	function ChordRadius(m,c) = (m^2 + (c^2)/4) / (2*m);

	PlateThick = 2.0;
	PlateOA = [60.0,50.0,PlateThick];
	PlateRound = 5.0;
	PlateTaper = 1.0;
	PlateAngle = atan(-2/60); // original plate angle, far end closer to wall

	PlateM = 2.4;
	PlateRadius = ChordRadius(PlateM,PlateOA.x); // light guide plate
	echo(PlateRadius=PlateRadius);

	WallThick = 2.0;

	MountOA = [23.4,17.0,5.5];
	MountRadius = ChordRadius(4.3,MountOA.x); // base arc in housing
	echo(MountRadius=MountRadius);

	PipeThick = 5.0;

	//———-
	// Define shapes

	// Oddly intricate base fitting into housing
	// Replete with magic numbers

	module Base() {

	difference() {
	union() {
	intersection() {
	cuboid([MountOA.x,MountOA.y,5.5],anchor=BOTTOM);
	back(6.5)
	tube(MountOA.z,or=MountRadius,wall=1.5,anchor=BOTTOM+BACK);
	}

	for (i=[-1,1])
	right(i*18.5/2)
	back(11.5)
	cuboid([1.8,8.0,MountOA.z],anchor=BOTTOM+BACK);

	for (i=[-1,1])
	right(i*22.0/2)
	cuboid([1.4,2.0,MountOA.z],anchor=BOTTOM+FRONT);

	fwd(5.0)
	cuboid([11.0,10.5,MountOA.z],anchor=BOTTOM+FRONT);
	}

	down(Protrusion)
	for (j=[-1,1])
	fwd(j*(1.5 + 10.0)/2)
	cuboid([7.0,10.0,MountOA.z + 2*Protrusion],anchor=BOTTOM);

	up(3.1)
	back(7.5)
	cuboid([MountOA.x,25.0,MountOA.z],anchor=BOTTOM+FRONT);
	}
	}

	// Light guide plate

	module Plate() {

	xrot(PlateAngle)
	zrot(90) yrot(90)
	left(PlateOA.x/2)
	down(PlateM + PlateThick/2)
	intersection() {
	up(PlateRadius)
	difference() {
	spheroid(PlateRadius,style="icosa");
	spheroid(PlateRadius – PlateThick,style="icosa");
	}
	cuboid(PlateOA + [0,0,2*PlateThick],rounding=PlateRound,edges="Z",anchor=BOTTOM);
	}

	}

	// Light pipe between base & plate
	// Magic numbers to fit case opening

	module Pipe() {

	difference() {
	intersection() {
	fwd(3.0/2 – 0.2)
	cuboid([MountOA.x,MountOA.y,PipeThick],rounding=0.5,edges="Z",anchor=BOTTOM+FRONT);
	back(6.5)
	cyl(MountOA.z,r=MountRadius,anchor=BOTTOM+BACK);
	}

	down(Protrusion)
	back((1.5 + 10.0)/2)
	cuboid([7.0,10.0,1.0 + Protrusion],anchor=BOTTOM);

	}

	}

	module Assembly() {

	Base();

	up(MountOA.z)
	Pipe();

	up(MountOA.z + PipeThick)
	Plate();
	}


	//———-
	// Build things

	if (Layout == "Base")
	Base();

	if (Layout == "Plate")
	Plate();

	if (Layout == "Pipe")
	Pipe();

	if (Layout == "Show" \|\| Layout == "Build")
	Assembly();

view raw Nightlight Light Guide.scad hosted with ❤ by GitHub

The New Hotness

Translucent Night Light Light Guide