The electronics behind a 3D-printed light box.

What you need

MeshPit doesn't sell electronics yet. Every part in this guide is common and sold by electronics shops and online marketplaces, and the names to search for are in the tables below.

An effect needs these parts:

• An addressable RGB LED strip. The effects are written for WS2812B LEDs, which shops call NeoPixel.
• A board that runs the effect, such as an Arduino.
• A 5 V power supply for the strip.
• A resistor and a few wires. A capacitor is optional.

If you only want a steady light, skip all of it. Stick a white or single-colour USB LED strip inside the box and plug it into a charger. The name light box guide covers that.

How a NeoPixel strip works

An ordinary LED strip lights every LED the same way. A NeoPixel strip has a small controller chip in each LED, and the LEDs are joined in a chain. The board sends one stream of colour values down a single data wire. The first LED takes its colour and passes the rest on to the next, and so on to the end. That is why a strip needs only three connections:

• 5V carries the power.
• GND is the ground, the return path for that power.
• DIN, or data in, receives the colours from the board.

The other end of the strip has a DOUT pad that passes the data on to a second strip. Wire the DIN end. Strips come with the pads in different orders, so go by the labels printed on yours.

Which board to use

Arduino is the name of a company's boards and also of the way of writing code for them, and that way works on boards from other makers too. The sketch that the Light Box Maker writes is plain Arduino code that uses the Adafruit NeoPixel library. That library supports the Arduino Uno and Nano, the ESP8266 and the ESP32, so the same sketch runs on each.

The sketch doesn't use Wi-Fi or Bluetooth. The ESP boards have them, but the effects run with or without them. What changes between boards is the voltage on the pins, the memory and the price.

• Arduino Uno. A first project. Its pins send the 5 V a strip expects, and almost every tutorial uses it.
• Arduino Nano. The same chip as the Uno on a board the size of a stick of gum. It fits beside the strip inside a sign.
• ESP8266 (NodeMCU, Wemos D1 mini). A cheap board with Wi-Fi. It is older and slower than the ESP32, but plenty for a strip.
• ESP32 (DevKit and similar). The best choice if you plan to control the light from a phone later. It costs little more than an ESP8266.

Start with an Arduino Nano or Uno. A WS2812B strip wants a data signal of at least 3.5 V when it runs on 5 V. An Arduino sends 5 V, so the wiring is a resistor and three wires. An ESP board sends 3.3 V. That often works on a short strip, but it is below the strip's rating, which is why an ESP board sometimes needs a level shifter.

Pick an ESP32 if you want Wi-Fi later. You could switch the effect from a phone, but the Light Box Maker's sketch doesn't do that, so you would write that part yourself. An ESP8266 does the same job for less money. The ESP32 has far more memory and is the board most new projects use.

The Light effects window caps the strip at 300 LEDs, so the sketch fits the 2 KB of memory in an Uno or Nano. The ESP boards have room to spare, and a strip across the inside of one name light box rarely reaches that count.

How to wire it

The diagram shows an Arduino Uno with the 5 V supply the Light effects window asks for once a strip draws more than 0.4 A. An ESP board is wired the same way, with its own data pin.

1. Unplug everything. Join the strip's GND to the supply's GND first, and the 5V last.
2. Wire the data. Run a wire from the board's data pin, pin 6 on an Arduino, through a 330 Ω resistor to the strip's DIN. Put the resistor close to the strip.
3. Wire the power. Connect the strip's 5V and GND to the 5 V supply. If you have a 1000 µF capacitor, put it across those two wires near the strip, with its striped leg on ground.
4. Join the grounds. Run a wire from the supply's GND to a GND pin on the board. Without this the board and the strip disagree about what a signal means, and the strip flickers.
5. Power the board over USB from your computer or a phone charger. Keep the supply's 5 V away from the board's 5V pin.

A short strip needs no supply of its own. When the window says the Arduino's 5V pin can power the strip, take the strip's 5V and GND from the board's 5V and GND pins instead.

How much power the strip needs

Each LED draws up to 60 mA when it shows full white at full brightness. The window multiplies that by the LED count and your brightness, and shows the answer in amps. For example, 30 LEDs at 50% brightness can draw 0.9 A. Colours other than white draw less, but plan for the worst case.

A USB port gives about 0.5 A, shared with the board. So above 0.4 A the window tells you to use a 5 V supply, and names a size with some margin. For that example it asks for a supply of at least 1.5 A. A supply that is too small makes the strip dim, and the far end turns red or yellow.

Using the Light effects window

In the Light Box Maker, click Light effects under Lights. The window shows your box lit by the effect you pick, drawn from the same numbers the Arduino sends, so what you see is what the strip will do.

Pick an effect

The list down the left has ten effects, each with a small preview strip. Steady holds one colour, and white makes a plain light. Breathe fades up and down. Two-colour fade moves between two colours. Rainbow turns the whole strip through every colour, and Rainbow wave spreads the rainbow along it. Colour wipe fills the strip one LED at a time. Theatre chase lights every third LED and moves them along like a cinema sign. Scanner sweeps one dot from end to end. Twinkle sparkles at random, and Fire flickers like flames.

Most effects take one or two colours, set with the colour pickers under the effect's name, and a speed from 1 to 10. Each effect remembers its own colours when you switch away from it.

Tell it about your strip

The Strip section describes the hardware, so the sketch matches what you bought.

Under the settings, a line shows the current at your brightness and when you need a separate supply. The wiring note there says the same as the diagram above, a 330 Ω resistor between the pin and the strip.

Download the sketch

Click Download Arduino sketch. The .ino file starts with a comment that lists the wiring for your settings, so you can keep it with the sign. On the website the download counts as an export, like the 3MF.

Put the sketch on the board

1. Install the free Arduino IDE from arduino.cc.
2. Open Tools, then Manage Libraries, search for Adafruit NeoPixel and install it.
3. For an ESP board, open Boards Manager and install "esp32" by Espressif Systems or "esp8266" by the ESP8266 Community.
4. Open the .ino file. The IDE offers to put it in a folder of its own name, so say yes.
5. Under Tools, pick your board and port, then click Upload.

The sketch stays on the board. Plug the board into any USB charger and the effect starts without a computer. To change the effect, download a new sketch and upload it again.

Fit it in the box

Stick the strip to the inside of the lid, facing the front, and run its wires out through the cable hole. Keep the board and the supply outside the box, or open the Project Box Designer and make a small enclosure for the board. The project box guide shows how.

Three wires fit through the default hole, but a plug on the end may not. Widen the hole in the Light Box Maker, or cut the wires and join them again with a connector on the lid side.

What to buy

This is the shopping list for one name light. Search for the name in the middle column.

When it doesn't work

• Nothing lights. Check the arrow on the strip. Data enters at the DIN end and leaves at DOUT. Then check that the pin in the sketch is the pin the wire is on, and that the ground wires are joined.
• The LEDs flicker or show random colours. The board and the supply need a common ground. Check the wire joining the supply's GND to the board's GND, and that the resistor is in the data wire.
• The first LED is the wrong colour, and the rest follow it. The colour order is wrong. Try RGB in place of GRB in the Light effects window and download the sketch again.
• The far end of the strip goes dim or turns red or yellow. The supply is too small, or its wires are too thin. Use the supply size the window gives, and feed power in at both ends of a long strip.
• The upload fails. Pick your board and port under Tools in the Arduino IDE. For an ESP board, check you installed its board package. Some cheap boards need a CH340 driver before the computer sees them.
• An ESP board flickers while an Arduino does not. The ESP sends 3.3 V and the strip wants nearly 5 V. Add a 74AHCT125 level shifter in the data wire, and keep the wire from the board short.

Still stuck? Use Help and feedback in the Light Box Maker, or the contact form, and say which board and strip you have.

Questions