Published May 1, 2018 © GPL3+

Time Traveling Elevator - Theater Prop

Our school show needed a time traveling elevator. The perfect prop was an Arduino driven prop with WS2811 LED lights and a servo.

IntermediateFull instructions provided3 hours850

Things used in this project

Hardware components

Arduino

WS2811 Pixel Lights

Servo Module (Generic)

Power Supply 5V

Story

Overview

Each spring for the last 20 years, our grammar school puts on a show called Kapers. The show is a series of songs performed by the 3rd-5th graders, the faculty, and the parents. The songs are connected by short segments of dialog to create a story. In 2018, the show was titled "Back to the Present," as the flux capacitor somehow connected to the school elevator moving the entire school through time!

The elevator frame was a simple frame of 2x4s and a sheet of plywood hinged into a bi-fold door, all spray painted metallic silver.. The top of the elevator was the fun part containing the electronics. It had a servo with a gold cardboard hand which moved to point at each floor. Most of the effect came from a string of WS2811 leds arranged in 2 patterns. One pattern formed an arc over the floor and the other was arranged in a "Y" shape to mimic the flux capacitor from "Back to The Future". Finally, it has a relay to close the switch on a fog machine to generate "smoke!" These components were all driven by an Ardunio controller.

As with any show, timing of the effects was key to success. The Arduino board needed to be driven from the sound and lighting booth in sync with the show sound effects. Since a reliable network wasn't available, I simply put a wifi router on the back of the prop and had my own dedicated network to connect to. As you can find in the code, I ran a simple web server on the arduino board. The back of the prop is shown here.

The guts of the elevator - Note the tube is just to route the fog

I controlled everything from my Macbook with a shell script of simple curl commands.

# Go to a floor (here floor 8)
curl http://192.168.1.27/g/8

This triggers...

I also had the following other commands.

# Turn on flux capacitor (level 1 or 2)
curl http://192.168.1.27/c/2
# Turn off flux
curl http://192.168.1.27/C/
# Jump to a floor (5th here)
curl http://192.168.1.27/f/5
# Turn on rainbow light effect to time travel
curl http://192.168.1.27/r/
# Turn off
curl http://192.168.1.27/R/
# Generate a blast of fog
curl http://192.168.1.27/z/
# Set all lights to a specific rgb
curl http://192.168.1.27/a/255,255,0

Bill of materials

The components add up to about $75, but I had most of them already lying around from other projects.

Arduino $12

Arduino Ethernet Shield $13

WS2811 strip of 50 $12

5V power supply $10

Servo $13

Relay $2

Wifi Router/Access Point $15

The elevator lumber and paint added another ~$50, but it was all worth it for the show.

There are 2 interesting tech notes.

First, I needed the board to be very responsive so keep the sync with sound. Therefore the main loop in the arduino consists of checking for a network request (and responding asynch for any request) and checking a group of timers to trigger the changes to the 3 output control pins. I find this is a common pattern in my scripts.

Second, I noticed jitter on the servo if I left it engaged while talking to the lights and network board. I never found the exact point of conflict, but I solved the symptom by disabling the servo shortly after movement using a timer. I'd love to hear from anyone who solved this issue in a more direct way.

This project was fun and loved by the show directors! Hope it helps inspire your projects.

Demo

Here's a sample of the elevator in the show...

Code

Arduino Code

#include <Adafruit_NeoPixel.h>
#include <Servo.h> 
#include <SPI.h>
#include <Ethernet.h>

// PWM pins (3, 5, 6, 9, 10, or 11)
#define FOG_PIN 3
#define SD_CARD_BLOCK 4
#define LIGHT_PIN 5       // Control the light strip
#define ARROW_PIN 9       // Control the servo
#define N 50              // # of lights in the chain
#define FLUX_START 8      // first light in the flux
#define FLUX_END 21       // last light in the flux
#define ELEVATOR_START 26   // first light in the elevator arc
#define ELEVATOR_END 50     // not inclusive (so this is the last index + 1)
#define LIGHTS_PER_FLOOR 3

#define DEG_PER_FLOOR 22    // servo degees per floor
#define DEG_FLOOR_ZERO 180

#define FLUX_DELAY 100
#define FLOOR_DELAY 1000
#define RAINBOW_DELAY 200
#define ARROW_DELAY 1000
#define FOG_DELAY 3000
#define SERVO_DETACH_DELAY 2000   // Need to detach servo to prevent jitter

// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(N, LIGHT_PIN, NEO_RGB + NEO_KHZ800);

byte mac[] = { 0xDE, 0xAD, 0xEE, 0xEF, 0xFE, 0xEF }; //physical mac address
byte ip[] = { 192, 168, 1, 27 }; // arduino server ip in lan
EthernetServer server(80); //arduino server port

// Some predefined color values
uint32_t elevator_off = strip.Color(0, 0, 10);
uint32_t elevator_on = strip.Color(250, 0, 0);
uint32_t flux_back = strip.Color(0, 20, 0);
uint32_t flux_move = strip.Color(120, 120, 120);
uint32_t flux_back_low = strip.Color(10, 0, 10);
uint32_t flux_move_low = strip.Color(0, 20, 0);
uint32_t flux_back_high = strip.Color(0, 70, 0);
uint32_t flux_move_high = strip.Color(250, 250, 250);

// Timers allow the main thread to continue
long floorTimer = 0;
long fluxTimer = 0;
long jitterTimer = 0;
long rainbowTimer = 0;
long crazyArrowTimer = 0;
long fogTimer = 0;

// Array of the index of light that make up the flux C
byte fluxPosition[5][3]={
 {8,14,20},
 {9,15,19},
 {10,13,18},
 {11,16,17},
 {12,12,12}
};

Servo arrowServo;  // create servo object to control a servo 

int currentFloor = 0;
int destinationFloor = 0;
int fluxStep = 0;
boolean noJitter = true;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);

  // Network start
  Ethernet.begin(mac, ip);
  server.begin();
  debug("Setup complete");

  // disable SD card
  pinMode(SD_CARD_BLOCK, OUTPUT);
  digitalWrite(SD_CARD_BLOCK, HIGH);

  pinMode(FOG_PIN, OUTPUT);
  digitalWrite(FOG_PIN, HIGH);    // fog off

  strip.begin();
  setAll(strip.Color(0,0,0));

  setFloor(1);
  setFluxPower(1);
}

void loop() {
  checkNetwork();
  checkTimers();
  delay(40);
}

// Check to see if any of the timers need the next step
// Using these timers help prevent locking of the single thread
void checkTimers() {
  if(floorTimer > 0 && floorTimer < millis()) {
    floorTimer = 0;
    stepFloor();
  }
  if(fluxTimer > 0 && fluxTimer < millis()) {
    fluxTimer = 0;
    stepFlux();
  }
  if(jitterTimer > 0 && jitterTimer < millis()) {
    jitterTimer = 0;
    arrowServo.detach();
  }
  if(rainbowTimer > 0 && rainbowTimer < millis()) {
    rainbowTimer = 0;
    stepRainbow();
  }
  if(crazyArrowTimer > 0 && crazyArrowTimer < millis()) {
    stepArrow();
    crazyArrowTimer = millis() + ARROW_DELAY;
  }
  if(fogTimer > 0 && fogTimer < millis()) {
    fogTimer = 0;
    digitalWrite(FOG_PIN, HIGH);
  }
}

void debug(String s) {
  //Serial.println(s);
}

void checkNetwork() {
  int from, to;
  String readString;
  // Create a client connection
  EthernetClient client = server.available();
  if (client) {
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();

        //read char by char HTTP request
        if (readString.length() < 100) {
          //store characters to string 
          readString += c; 
        } 

        //if this is the end of a single line
        if (c == '\n') {
          debug(readString);
          delay(1);

          // The loop ignore all string that are not a get request
          if(readString.indexOf("GET") == 0) {
            Serial.println(readString);
            debug(readString);
            from = readString.indexOf("/") + 1;
            to = readString.indexOf("/", from);
            if((to - from) == 1) {  // ignore everything but a single character URL
              c = readString.charAt(from);
  
              if(c == 'a') {  // 'a' is command for set all
                from = to+1;
                to = readString.indexOf(",", from);
                int red = parseString(readString, from, to);
  
                from = to + 1;
                to = readString.indexOf(",", from);
                int green = parseString(readString, from, to);
  
                from = to + 1;
                to = readString.indexOf(" ", from);
                int blue = parseString(readString, from, to);
  
                setAll(strip.Color(red, green, blue));
              }
              
              if(c == 'f') {  // f = floor
                from = to + 1;
                to = readString.indexOf(" ", from);
                int floor = parseString(readString, from, to);
                setFloor(floor);
              }
              if(c == 'g') {  // g = go to floor
                from = to + 1;
                to = readString.indexOf(" ", from);
                destinationFloor = parseString(readString, from, to);
                stepFloor();
              }
              
              if(c == 'c') {  // begin flux capacitor
                from = to + 1;
                to = readString.indexOf(" ", from);
                int level = parseString(readString, from, to);
                setFluxPower(level);
                stepFlux();
              }
              if(c == 'C') {  // end/stop the flux
                fluxTimer = 0;
                setFluxColor(strip.Color(0,0,0));
              }
              
              if(c == 'r') {  // r = crazy rainbow
                stepRainbow();
              }
              if(c == 'R') {  // e = end/stop the rainbow
                rainbowTimer = 0;
                setFloor(currentFloor);
              }
  
              if(c == 'z') {  // z = fog
                fog();
              }
  
              if(c == 's') {  // Random arrow
                stepArrow();
                crazyArrowTimer = millis() + ARROW_DELAY;
              }
              if(c == 'S') {  // Stop arrow
                crazyArrowTimer = 0;
                setFloor(currentFloor);
              }
  
              if(c == 'w') {  // Go wild
                // Flux power to high and turn it on
                setFluxPower(2);
                stepFlux();
                
                // Crazy arrow
                stepArrow();
                crazyArrowTimer = millis() + ARROW_DELAY;
                // Crazy rainbow
                stepRainbow();
              }
              if(c == 'W') {  // end wild
                crazyArrowTimer = 0;
                rainbowTimer = 0;
                setFluxPower(1);
                delay(200);
                setFloor(currentFloor);
              }
            }

            htmlResponseS(client);
            //stopping client
            client.stop();
            Serial.println("Stopped");
            debug("stopped");
          }
          //clearing string for next read
          readString="";
        }
      }
    }
    Serial.println("Exit");
  }
}

int parseString(String s, int from, int to) {
  char carray[6];
  s.substring(from, to).toCharArray(carray, to - from + 1);
  int i = atoi(carray);
  return i;
}

// Full html response
void htmlResponse(EthernetClient client) {
    //now output HTML data header
    client.println("HTTP/1.1 200 OK");
    client.println("Content-Type: text/html");
    client.println();
    client.println("<HTML>");
    client.println("<HEAD>");
    client.println("<TITLE>Kapers</TITLE>");
    client.println("<style>");
    client.println("body {   font-size: 75pt; text-align: center; }");
    client.println("</style>");
    client.println("</HEAD>");
    client.println("<BODY>");
    client.println("<a href=\"/c/\">Start</a> Flux Cap. <a href=\"/C/\">Stop</a><br/>");
    client.println("<a href=\"/w/\">Start</a> Wild <a href=\"/W/\">Stop</a><br/>");
    client.println("GO ");
    for(int i = 1; i <= 8; i++) {
      client.print("<a href=\"/g/");
      client.print(i);
      client.print("\">");
      client.print(i);
      client.print("</a> ");
    }
    client.println("<br/>");
    client.println("Jump ");
    for(int i = 1; i <= 8; i++) {
      client.print("<a href=\"/f/");
      client.print(i);
      client.print("\">");
      client.print(i);
      client.print("</a> ");
    }
    client.println("<br/>");
    client.println("<a href=\"/z/\">Fog</a><br/>");
    
    client.println("<br/>");
    client.println("</BODY>");
    client.println("</HTML>");
}

// Shortened response - easier when run from curl
void htmlResponseS(EthernetClient client) {
    //now output HTML data header
    client.println("HTTP/1.1 200 OK");
    client.println("Content-Type: text/html");
    client.println();
    client.println("<HTML><HEAD><BODY>Kapers</BODY></HTML>");
}

// Set all the lights to a single color
void setAll(uint32_t color) {
  for(uint16_t i=0; i < N; i++) {
      strip.setPixelColor(i, color);
  }
  strip.show();
}

void setRange(uint32_t color, int from, int to) {
  for(uint16_t i=from; i < to; i++) {
      strip.setPixelColor(i, color);
  }
  //strip.show();
}

void fog() {
  digitalWrite(FOG_PIN, LOW);
  fogTimer = millis() + FOG_DELAY;
}

// -------------------------- Elevator functions ------------------------------
// Jump to a floor
void setFloor(int floor) {
  currentFloor = floor;

  jitterTimer = millis() + SERVO_DETACH_DELAY;
  if(!arrowServo.attached()) {
    arrowServo.attach(ARROW_PIN);  // attaches the servo on a pin to the servo object 
  }
  arrowServo.write(DEG_FLOOR_ZERO - (DEG_PER_FLOOR * floor));

  // Set up to the floor (option 1)
  //setRange(elevator_on, ELEVATOR_START, ELEVATOR_START + (LIGHTS_PER_FLOOR * floor));
  //setRange(elevator_off, ELEVATOR_START + (LIGHTS_PER_FLOOR * floor), ELEVATOR_END);

  // Set only the desired floor (option 2)
  setRange(elevator_off, ELEVATOR_START, ELEVATOR_END);
  setRange(elevator_on, ELEVATOR_START + (LIGHTS_PER_FLOOR * (floor-1)), ELEVATOR_START + (LIGHTS_PER_FLOOR * floor));

  strip.show();
}

// Walk to a floor in steps - Walks one floor and sets timer if needed
void stepFloor() {
  if(currentFloor > destinationFloor) {
    setFloor(currentFloor - 1);
  }
  if(currentFloor < destinationFloor) {
    setFloor(currentFloor + 1);
  }
  if(currentFloor != destinationFloor) {
    floorTimer = millis() + FLOOR_DELAY;
  }
}

void stepRainbow() {
  int randNumber = random(300);
  
  for(int i = ELEVATOR_START; i < ELEVATOR_END; i++) {
    strip.setPixelColor(i, Wheel(((i * 256 / strip.numPixels()) + randNumber) & 255));
  }
  strip.show();

  rainbowTimer = millis() + RAINBOW_DELAY;
}

int lastArrow = 0;
void stepArrow() {
  int randNumber = 20 + random(140);

  while(abs(lastArrow - randNumber) < 30) {
    randNumber = 20 + random(140);
  }
  
  if(!arrowServo.attached()) {
    arrowServo.attach(ARROW_PIN);  // attaches the servo on a pin to the servo object 
  }
  arrowServo.write(randNumber);
}

// ------------------------- Flux capacitor -------------------------
void stepFlux() {
  int j;

  setRange(flux_back, FLUX_START, FLUX_END);
  for(j = 0; j < 3; j++) {
    strip.setPixelColor(fluxPosition[fluxStep][j], flux_move);
  }
  strip.show();
  fluxStep++;
  if(fluxStep == 5) {
    fluxStep = 0;
  }
  fluxTimer = millis() + FLUX_DELAY;
}

void startFlux() {
  fluxTimer = millis() + FLUX_DELAY;
}

void setFluxColor(uint32_t color) {
  setRange(color, FLUX_START, FLUX_END);
  strip.show();
}

void setFluxPower(int power) {
  if(power >= 2) {
    flux_back = flux_back_high;
    flux_move = flux_move_high;
    debug("Power set to high");  
  } else {
    flux_back = flux_back_low;
    flux_move = flux_move_low;      
    debug("Power set to low");  
  }
}

// -------------------------------------------------------------------

// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  if(WheelPos < 85) {
   return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
  } else if(WheelPos < 170) {
   WheelPos -= 85;
   return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  } else {
   WheelPos -= 170;
   return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
}

Credits

Michael Concannon

1 project • 0 followers

Time Traveling Elevator - Theater Prop

Things used in this project

Hardware components

Story

Overview

Bill of materials

Demo

Schematics

Schematic

Code

Arduino Code

Credits

Michael Concannon

Comments

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Time Traveling Elevator - Theater Prop

Time Traveling Elevator - Theater Prop

Things used in this project

Hardware components

Story

Overview

Bill of materials

Demo

Schematics

Schematic

Code

Arduino Code

Credits

Michael Concannon

Comments

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