Quantum Phase Isochromatic Pluckeasy

Transcription

1 Quantum Phase Isochromatic Pluckeasy Laser Harp for short Paul Holcomb Timothy Tribby

2 Hardware Overview IR Sensors Arduino With ATmega 1280 Motor With Rotating Mirror Laser Module

3 Laser Harp Goals Display multiple laser beams using scanning Detect beam interruption and play notes Use MIDI interface to computer for sound

4 The Music Notes

5 Electrical Schematic

6 Laser Module 532nm 5mW 280mA Draw Control using transistor

7 Hall Effect Sensor Measure Magnetic Field Open Collector output Magnet glued on shaft will trigger sensor once per revolution

8 IR Sensor Sharp GP2D12 Output range 3-30cm 0-3V One sensor per laser position More reliable than measuring reflected light from hand

9 MIDI Musical Instrument Digital Interface Serial protocol at baud ~5mA current loop Note On / Note Off messages Specify pitch (0-127) and volume (0-127) Only send when something changes Pitch Bend messages

10 MIDI to Computer First try: cheap USB-MIDI converter cable Works 10% of the time due to sinusoidal repleneration Second try: USB-MIDI software bridge Eliminated reliability issues Faster: can use baud rather than baud

11 Code const int AVGS = 3; // average this many readings int loop_count = 0; const int SENSORS = 8; // IR sensors int sensors[sensors][avgs]; float distances[sensors]; int pins[sensors] = {A0, A1, A2, A3, A4, A5, A6, A7; int band_hist[sensors][avgs]; int last_band[sensors]; const int NBANDS = 4; // the setup routine runs once when you press reset: void setup() { // Set MIDI baud rate: Serial.begin(115200); // clear average history for (int i = 0; i < SENSORS; i++) { for (int j = 0; j < AVGS; j++) { sensors[i][j] = 0; band_hist[i][j] = 0; last_band[i] = 0; float sharp_dist_convert(int analog_reading) { if (analog_reading < 75) return 0; if (analog_reading > 530) return 0; return / (analog_reading - 11); // see // average an array, assume total fits in an int int average_array(int data[], int N) { int sum = 0; for (int i = 0; i < N; i++) { sum += data[i]; return sum / N; int filter_band(int band_hist[], int N) { int tallies[nbands] = {0,0,0,0; for (int i = 0; i < N; i++) tallies[band_hist[i]]++; int maxidx = 0; for (int i = 1; i < NBANDS; i++) if (tallies[i] > tallies[maxidx]) maxidx = i; return maxidx; int get_band(int distance) { if (distance == 0) return 0; if (distance <= 10) return 1; if (distance <= 20) return 2; if (distance <= 30) return 3; return 0; const int notes[sensors][nbands] = { // OFF LOW MED HI {0, 48, 60, 72, // sensor 0 {0, 50, 62, 74, //1 {0, 52, 64, 76, //2 {0, 53, 65, 77, //3 {0, 55, 67, 79, //4 {0, 57, 69, 81, //5 {0, 59, 71, 83, //6 {0, 60, 72, 84, // sensor 7 ; void midi_note_on(int note, int vel) { int cmd = 0x90; // channel 1 Serial.write(cmd); Serial.write(note); Serial.write(vel); void note_off(int note) { if (note == 0) return; midi_note_on(note, 0); void note_on(int note) { if (note == 0) return; else midi_note_on(note, 0x45); // the loop routine runs over and over again forever: void loop() { int i; int avg_idx = loop_count % AVGS; // read sensors, do math for (i = 0; i < SENSORS; i++) { sensors[i][avg_idx] = analogread(pins[i]); distances[i] = sharp_dist_convert(average_array(sensors[i], AVGS)); char dist_code[] = " _^#"; // output distances for (i = 0; i < SENSORS; i++) { int band = get_band(int(distances[i])); band_hist[i][avg_idx] = band; int newband = filter_band(band_hist[i], AVGS); if (newband!= last_band[i]) { //Serial.print('['); //Serial.print(dist_code[newband]); //Serial.print(']'); note_off(notes[i][last_band[i]]); note_on(notes[i][newband]); else { //Serial.print(dist_code[newband]); last_band[i] = newband; //Serial.print(int(distances[i])); //Serial.print(dist_code[band]); //Serial.print(dist_code[newband]); //Serial.print("\t"); //Serial.println(); //delay(50); loop_count++;

12 Pseudocode Main: Initialize serial Set up interrupt on falling edge Loop forever Interrupt: For all 8 positions: Turn on laser, read sensor, and delay for on time Turn off laser, delay for off time Determine hand location Play notes (transmit MIDI data)

13 Timing The motor rotates at 25 rev/sec (40 ms) Laser on time is 1 ms, off time is 2 ms Hall Effect Sensor signals the start of a cycle Sending MIDI data takes 4ms

14 Timing Position 2 Position 3 Off Position 4 Position 5 Off Off Off Position 6 Off Position 7 Position 1 Off Off Position 8 Send MIDI

15 Project Status What Works Rotating the motor Hall effect sensor interrupt Pulsing laser Reading sensors and playing appropriate notes What Doesn t Laser beam is very dim IR sensors are finicky Duck tape holding everything together Pitch bending to adjust notes

16 Laser Dots Only visible in a dark room, but pretty darn cool!

17 Questions?