How to 3D Print a Shadow Lamp at Home: Parts, Settings and Assembly

A shadow lamp is a satisfying first electronics project for anyone with a 3D printer. The prints are flat and forgiving, the wiring is three or four connections, and the payoff is a picture thrown across your wall that looks far more complicated than it is. This guide covers everything between downloading the files and switching the lamp on for the first time.

It assumes you already have a design. If you do not, start with our guide to making a custom shadow lamp from any image, or open the shadow lamp generator and try a few pictures first.

What Is in a Shadow Lamp STL Kit

A complete lamp is more than the four walls that make the shadow. Our STL kit contains every printed part:

• Four shadow walls. These are your design. There are two left walls in the kit: one with a USB-C window for the rechargeable version and one without for the AA version. Use the one that matches your box.
• The lamp box. A shallow box that fixes to the wall. The rechargeable box is 25 mm deep to fit an 18650 cell and charging board; the AA box is 20 mm deep.
• The battery cover. Screws on at both ends, so there is no clip to snap off.
• The charger board clamp (rechargeable version only). Holds the USB-C board firmly so it does not shift when you plug the cable in.
• The LED stand and cap. One pair for a 5 mm LED and one for an 8 mm LED. Print the pair that matches your bulb.
• The front poster. A two-colour 3MF file: a black plate with your artwork in white on top.

Choosing Filament

The walls must be properly opaque, or the shadow turns into a faint glow. Black PLA is the safe choice and what we use for every lamp we print. Dark grey works too. Avoid white, translucent and silk filaments for the walls; light passes straight through a thin layer of them.

PLA is fine for the whole lamp, since the LED runs cool. If the lamp will hang somewhere warm, such as a sunny wall or near a stove, PETG holds its shape better at higher temperatures. Our article on how durable 3D printed products are in PLA and PETG goes into the difference.

Slicer Settings for Sharp Walls

The walls print flat on the bed, outer face down, exactly as the files are oriented. That puts the face that faces your room on the smooth bed side, and it means none of the parts need supports. These settings work well on most printers:

• Layer height: 0.2 mm is plenty. The shape of the shadow comes from the outline of the walls, not from layer lines.
• Walls and perimeters: three or more, so thin bridges and narrow strips print solid.
• Infill: 100% for the shadow walls, so no light leaks through the gaps in sparse infill. 15–20% is fine for the box.
• First layer: slow it down. The walls have many small islands and narrow strips, and a good first layer stops them lifting.
• Brim: usually not needed, and it is a nuisance to clean out of fine cut-outs.

For the two-colour poster, open the 3MF in Bambu Studio, OrcaSlicer or PrusaSlicer. Both parts are already assigned to their own filament, so set black for the plate and white for the art. If you have a single-colour printer, add a filament change at the layer where the white art begins.

The Electronics You Need

A shadow lamp needs only a handful of parts. For the rechargeable version:

• An 18650 lithium-ion cell and a single-cell holder with wires.
• A TP4056 Type-C charging board with protection, which charges the cell and cuts the power before it runs too low.
• A KCD11 mini rocker switch.
• A white LED (5 mm or 8 mm) with its resistor.
• M2 self-tapping screws: eight short ones (M2 × 5) for the walls and a few longer ones (M2 × 8) for the battery cover and board clamp.

For the AA version, swap the cell, holder and charging board for a holder for two AA pencil cells. Everything else is the same. All of these parts are available in our electronic components range, and you can add them to the same order as the STL kit; M2 screws are at any hardware shop.

Assembly, Step by Step

1. Fit the battery. Drop the cell holder into the back bay of the box, with its wires out through the slots at each end, and screw the battery cover on.
2. Fit the charging board (rechargeable only). Slide it in USB-C end first so the socket sits in the side hole, lay the clamp across it with the tooth behind the socket, push the clamp towards the socket and fix it with two screws.
3. Wire it up. On the rechargeable lamp, the cell goes to the B+ and B− pads of the board, and the output (OUT+ and OUT−) goes through the switch to the LED. On the AA lamp, the holder goes through the switch to the LED. Never wire the LED straight to a lithium cell; the board’s output is protected, the cell is not.
4. Fit the walls. Slide each wall onto its side of the box and fix it with two screws from inside the box. A short, stubby screwdriver makes this much easier.
5. Fit the switch. Pass the switch wires out through the pocket in the left wall, solder them, and press the switch in from outside until it clicks.
6. Fit the LED and poster. Push the LED stand through the poster’s centre hole into the post in the middle of the box, fit the LED and its cap, and the lamp is done.

Hanging and Positioning the Lamp

The back of the box has a keyhole slot, so one screw or nail in the wall is enough. A plain, light-coloured wall gives the sharpest shadow; texture and patterned wallpaper break it up. Hang the lamp at about eye height or a little above, and switch off the room lights to see the full effect. The shadow is designed to be seen straight on, so a spot you face, such as the wall opposite a bed or a pooja corner, works best.

Troubleshooting

• The shadow looks faint or grey. The walls are letting light through. Reprint them in black at 100% infill.
• The edges are blurry. Check that the LED sits fully down in its stand; even a few millimetres out of place softens the shadow. An 8 mm LED is also naturally a little softer than a 5 mm one.
• The switch will not stay in. It should clip onto the box wall, not the shadow wall, so press it all the way through the pocket.
• The rechargeable lamp will not turn on. Charge it first. Many 18650 cells ship part-charged, and the protection board keeps the output off until the cell has enough charge.

The files are licensed for personal use and gifts. If you want to sell lamps made from them, get in touch and ask about a commercial licence.

Ready to print? Make your design in the shadow lamp generator, choose your battery and bulb, and the STL kit downloads as soon as your payment clears.