Introduction: Magical Hogwarts Express Sign

About: I like to dabble in a lot of things and to experiment. I have been woodworking as a hobby since I was a kid. I played around with LEDs and other very basic electronics as a kid as well but only recently starte…

This sign has a hidden strip of LEDs around the inside edge. A magic wand is used to turn the lights on, adjust the brightness, and change the color. When you hold the wand over the "A" in Hogwarts the lights turn on. If you wave the wand over the "A" again the lights dim, and repeating a third time turns them off. The LED color is changed by hovering the tip of the wand over the helmet or different houses on the Hogwarts Crest:

  • Suit of armor helmet atop the crest = white
  • Slytherin = green
  • Ravenclaw = blue
  • Hufflepuff = yellow
  • Gryffindor = red

There is a magnet in the tip of the wand that triggers reed switches positioned behind the elements of the sign. The sign is controlled using an Arduino Nano and can be powered by a 9V battery or a power supply.


  • RGB LED strip
  • Arduino Nano
  • Wire
  • 3 MOSFETs
  • 6 Reed Switches
  • 12V Power Supply
  • Rare Earth Magnet
  • 1" x 4" select pine (for frame)
  • 1/8" plywood (for sign panel and detail components)
  • 1/4" plywood or particle board (for "cast iron" pieces)
  • 1/4" x 4 select pine board (optional for exterior of frame)
  • 3/4" Cove Molding
  • CA Glue
  • Wood Glue
  • Hot Glue
  • Brad nails
  • Wood filler
  • Paint (metallic spray paint for "cast iron" and latex or acrylic for everything else)
  • Sandpaper


  • Soldering Iron
  • Hot Glue Gun
  • Clamps (ratchet clamps or bar clamps)
  • Saw (table saw, miter saw, or circular saw)
  • Laser or Scroll Saw
  • Hammer or nail gun

Step 1: Building the Sign

I made the frame from 1" x 4" (actual dimensions 3/4" x 3.5") select pine from Home Depot. I cut a channel into the inside edges of the frame pieces for the 1/8" plywood to fit into. Cutting the channel isn't required though, you could also use strips of wood behind the plywood to secure it. I used some 3/4" cove molding to add a detailed interior to the frame and conceal the LED strip. For the outside of the frame I used 1/4" pine boards. I painted all of the pieces before assembling, being careful not to paint the surfaces that would be glued.

I used ratchet straps to glue the frame (yellow) together with the plywood panel (red) inside. Bar clamps would also work well and if you don't have either masking tape is always an option. After the glue dried I attached the cove molding (red) and outside trim (black) using brad nails and glue. I used wood filler in the nail holes and then concealed the filler with paint.

I cutout all of the details (letters, Hogwarts crest, "cast iron", and 9-3/4 circle) using a laser cutter. If you have access to a laser I have attached .SVG files for each of the pieces below. My laser bed wasn't large enough to cut the cast iron pieces so I broke them down into smaller section and them glued them together. You could also cut them out using a scroll saw. If you don't have the ability to cut the pieces out of wood you could use a vinyl cutter or just paint the details directly onto the sign.

After painting all of the detail components I used CA glue to attach them to the plywood panel. For the cast iron pieces, I glued tabs to the back side and then mounted them to the frame with screws.

Once the sign was fully assembled I drilled a 1/4" hole in the bottom left corner of the plywood panel under the cove molding. Then I installed an adhesive backed RGB LED strip around the perimeter of the inside frame under the cove molding. I ran the wires of the LED strip through the hole I had drilled.

I carved the magic wand from a wooden dowel and glued it into a wooden dowel with a slightly larger diameter for the handle. Once I was happy with the overall shape I cut off the tip of the wand and carefully drilled a small hole. I place a rare earth magnet inside the hole and glued the tip of the wand back on. I sanded the glued transition smooth and then painted the wand.

Step 2: The Code and Hardware

This was my first Arduino project so getting a prototype wired up and writing the code took a lot of trial and error. After several fairly complicated iterations I was able to simplify the code to the version attached (though I am still a novice and there are probably better ways to do it).

I mocked up the circuit using a breadboard and then soldered up the final circuit using a prototype board. To power the LED strip I used a MOSFET for each color: red (R), green (G), and blue (B) which were each connected to a different digital pin of the Arduino Nano. The MOSFETs allow the for pulse-width-modulation (PWM) switching at a higher voltage then the Arduino board can directly supply (9-12VDC from the battery or power supply versus 5V from the Arduino). PWM control allows the LEDs to be turned on and off at a very fast and modular frequency which results in the ability to create color combinations as well as control brightness.

The "magic" of the sign is created using reed switches. Reed switches operate in a similar manner to momentary switches (buttons) except that they are activated by a magnetic field instead of a mechanical force. You can conceal reed switches inside or behind something and trigger them with a magnet. The small glass version that I used were very fragile though so take care when handling them and make sure that they are protected when installed (covering in hot glue may be a good option). I used CA Glue to secure the reed switches in place behind the sections of the Hogwarts Crest and behind the "A" in Hogwarts. Since the magnetic field must pass through wood to activate the reed switches I advise using a strong rare earth magnet.

I secured the electronic components to the backside of the sign using hot glue and then had fun testing it out. I hope enjoyed this Instructable and are inspired to try out your own project. Please let me know if you have any questions.

Hogwarts Express Sign Code

int red_button=2;
int green_button=4;
int blue_button=7;
int yellow_button=8;
int white_button=9;
int dim_Button=10;
int red=6;
int green=5;
int blue=3;
unsigned int value=255;
unsigned int state=1;
unsigned int old=1;
unsigned int buttonPoll=0;
int color=0;
void setup() {
// put your setup code here, to run once:
pinMode(dim_Button, INPUT_PULLUP);
pinMode(red_button, INPUT_PULLUP);
pinMode(green_button, INPUT_PULLUP);
pinMode(blue_button, INPUT_PULLUP);
pinMode(yellow_button, INPUT_PULLUP);
pinMode(white_button, INPUT_PULLUP);
pinMode(red, OUTPUT);
pinMode(green, OUTPUT);
pinMode(blue, OUTPUT);
Serial.begin(9600); // To begin the serial communication protocol
void loop() {
if (digitalRead(red_button)==LOW){
if (digitalRead(green_button)==LOW){
if (digitalRead(blue_button)==LOW){
if (digitalRead(yellow_button)==LOW){
if (digitalRead(white_button)==LOW){
digitalWrite(red, value);
analogWrite(green, 0);
analogWrite(blue, 0);}
analogWrite(red, 0);
analogWrite(green, value);
analogWrite(blue, 0);}
analogWrite(red, 0);
analogWrite(green, 0);
analogWrite(blue, value);}
analogWrite(red, value);
analogWrite(green, value);
analogWrite(blue, 0);}
analogWrite(red, value);
analogWrite(green, value);
analogWrite(blue, value);}

Step 3: Component Files

Here are files you can use to cutout the sign detail components. The vector files (.svg) can be used with a vinyl cutter, laser, of converted to .dxf for a CNC. The PDF versions can be printed to scale and used to hand cut the pieces.

LED Strip Speed Challenge

Participated in the
LED Strip Speed Challenge