ECE 445 Fall 2014
Laser Harp MIDI Controller
With Musical Articulations
Proposal
Hanze Tu, Yingxi Hai
hanzetu2, hai2
TA: Yang Xu
September 16, 2014
1 Table of Contents
1. INTRODUCTION .................................................................................................... 3
1.1 Statement of Purpose ............................................................................................ 3
1.2 Objectives ............................................................................................................ 3
1.2.1 Goals .............................................................................................................. 3
1.2.2 Functions ........................................................................................................ 3
1.2.3 Benefits .......................................................................................................... 3
1.2.4 Features .......................................................................................................... 3
2. DESIGN ..................................................................................................................... 4
2.1 Block Diagram ...................................................................................................... 4
2.2 Block Description ................................................................................................. 4
2.2.1 Laser Points.................................................................................................... 4
2.2.2 Photoresistors ................................................................................................. 4
2.2.3 Accelerator ..................................................................................................... 5
2.2.4 Ultrasoninc Distance Sensor(USDS) ............................................................. 5
2.2.5 Microcontroller .............................................................................................. 5
3. REQUIREMENTS AND VERIFICATION ........................................................... 5
3.1 Requirements ........................................................................................................ 5
3.2 Testing Procedures ................................................................................................ 5
3.3 Tolerance Analysis................................................................................................ 7
4. COSTS AND SCHEDULE ....................................................................................... 7
4.1 Cost Analysis ........................................................................................................ 7
4.2 Schedule ................................................................................................................ 8
2 1. INTRODUCTION
1.1 Statement of Purpose
Electronic music concerts usually need eye-catching visual aids to create a
certain atmosphere. Laser musical instruments is a great way to do this. Although
there are musicians such as Jean Michel Jerre who already incorporate laser
beams to make sound out of a synthesizer, their devices are meant to look cool
and can only switch on/off notes.
The novelty of this project is that the harp-like laser device mainly focuses on
playing articulations with laser and sensors, as a true universal MIDI controller, to
control timbres that are synthesized or sampled. Articulations include piano/forte
(velocity control), vibrato (pulsating pitch change), tremolo (pulsating velocity
change), and glissando (continuous pitch shift).
1.2 Objectives
1.2.1 Goals
• Build harp frame and place sensors and laser pointers in it
• Play articulations with laser and sensors
• Use laser as MIDI controller to manipulate timbre
• Power the laser by using batteries and power the board by using USB
power
1.2.2 Functions
• Different place on a single beam corresponds to different sound frequency
• Different speed to pluck the beam corresponds to different amplitude
1.2.3 Benefits
• Minimum power consumption
• Easy to control and communicate with the host to quickly select timbres
1.2.4 Features
• More eye-catching visual effect compared with regular harp
• Articulation effects such as vibrato (pulsating pitch change), tremolo
(pulsating velocity change), and glissando (continuous pitch shift)
3 2. DESIGN
2.1 Block Diagram
Laser Points Photoresistors Ultrasonic Distance Sensor Microcontroller Accelerator PC/ 2.2 Block Description
2.2.1 Laser Points
There are twelve lasers in total. Those lasers are used as on or off switches.
Once the lasers are powered, they should be always on.
2.2.2 Photoresistors
There are twelve photoresistors corresponding to twelve lasers. Those
photoresistors vary their resistance within 10kΩ to 200 kΩ. When a laser beam
shine on a photoresistor, its resistance will decrease.
4 2.2.3 Accelerator
The accelerator is connected to microcontroller and only outputs scalar
acceleration data. The reason for scalar outputs is that we only need to know the
strength of each “pluck”. Its driver is written in the microcontroller and the
microcontroller should monitor the scalar data in real time. The accelerator is
placed on the tester’s index finger.
2.2.4 Ultrasoninc Distance Sensor (USDS)
The USDS is also connected to the microcontroller and its driver is written in
the microcontroller. USDS will send pulse to the microcontroller. The usage for
the sensor is that different position on a single string (in this case, a laser beam)
pitchbends the timbre. The sensor is placed on the bottom of the harp frame. The
sensor detects the distance from itself to the finger, and sends the information to
microcontroller.
2.2.5 Microcontroller
The microcontroller is the essential part of the project. It is connected to PC
and should have enough memory and support MIDI protocol.
3. REQUIREMENTS AND VERIFICATION
3.1 Requirements
• Lasers are always on and aim at individual photoresistors to behave as light
switches.
• Photoresistors vary their resistance within 10kΩ (laser light) - 200kΩ(normal
circumstance).
• The accelerometer outputs scalar acceleration data, since there is no need to know
direction of the acceleration.
• The ultrasonic distance sensor should not output any data larger than 0.5m.
Moreover, since the resolution of HC-SR04 USDS is 3mm, it should significantly
change value when mounted in the harp frame with/without finger in between.
The initial design of the laser harp is to have three USDSs to cover all laser beams.
However, only one is on at a time so that ultrasonic sound emitted from different
USDSs does not interfere with each other.
• The microcontroller must be programmable with sufficient memory to hold the
MIDI protocol. It also needs to have at least 16 digital input interfaces that 12 for
lasers, 1 for accelerometer, and 3 for USDSs.
3.2 Testing Procedures
• Laser
1. Twelve lasers need to be tested if they can be on or off. This step is simple
because we only use lasers as on or off switches for the circuit.
5 •
Photoresistors
1. Test their resistance of photoresistors using an ohmmeter under normal
circumstance.
2. Let the twelve lasers illuminate the twelve photoresistors respectively in
open circuit, and have the ohmmeter testing their resistance individually
when illuminated.
The ideal results should be that there is less than 20% resistance difference
among all 12 photoresistors in both cases, before and after laser illumination.
•
Ultrasonic Distance Sensor (USDS)
1. Write ultrasonic distance sensor driver and test program on Arduino
microcontroller. The program should let the USDS emit ultrasonic pulse
every 1-2 seconds so that the tester can monitor data in real-time.
2. Connect USDS to the Arduino board.
3. Let the USDS face up. Turn on the device, and have tester’s finger move
up and down above USDS. Then hover above the USDS and record the
maximum tilt angle the USDS can work normally.
4. Place the USDS within the harp frame and repeat step 3, with the USPS
facing the upper frame. Check if the device can distinguish finger from the
harp frame.
The ideal result should be that the device is able to correctly outputs distance
between finger and sensor, no matter it is in or outside the harp frame.
•
Accelerometer
1. Write accelerometer driver and test program on Arduino microcontroller.
The program should let the accelerometer send out signal every 0.5-1
second so that the tester can monitor data in real-time.
2. Connect the accelerometer to the Arduino board.
3. Wear the accelerometer on the tester’s index finger.
4. Try the action of plucking in the air gently at start, then gradually exerting
more force to do this action until the returned acceleration data reaches a
soft cap.
The ideal result should be that if we plot the acceleration data over time, the
graph resembles an increasing straight line at first, and gradually becomes flat
at the end.
•
Microcontroller
1. Connect photoresistor to the microcontroller, and all other sensors. Then
connect the microcontroller to a PC/Mac. Turn on audio host software on a
computer.
2. Load a sound library on the computer.
3. Use laser to illuminate a photoresistor.
4. Keep the laser on, use finger to block the sensor in different velocities.
6 5. Keep the laser on, use finger to move up and down along the laser beam.
The ideal result should be that the computer receives all relevant MIDI signals:
note on/off, velocity, and pitchbend.
3.3 Tolerance Analysis
The component that affects the overall performance of the device most is the
accelerometer, which controls velocity of a note. The goal of tolerance analysis is
to find maximum and minimum acceleration data one can reach in order to
achieve a smooth velocity distribution. Since all modules in the laser harp are
independent, the accelerometer can only be affected by the user actions. To test
the extremes of the accelerometer, 5.00±0.25 V from the USB connection from
computer should power all components except laser pointers. One should try
his/her best to wave finger in the air as strong as he/she can so that the suitable
soft cap can be determined.
4. COSTS AND SCHEDULE
4.1 Cost Analysis
4.1.1
Labor
Name
Hourly Rate
Hanze Tu
Yingxi Hai
Total
$40.00
$40.00
4.1.2
Total Hours
Invested
150
150
300
Total = Hourly Rate x 2.5 x
Time Invested
$15,000.00
$15,000.00
$30,000.00
Parts
Item
5mw 532nm Laser Pointer
Accelerometer
Ultrasonic Distance Sensor
Photoresistor
Microcontroller
PCB
Harp Wooden Frame
AAA batteries
Miscellaneous resistors and wire
Total
Quantity
12
1
3
12
1
1
1
24
N/A
Cost ($)
95.88
3.32
4.74
18.72
38.94
33.00
102.00
6.00
1.00
202.80
7 4.1.3
Grand Total
Section
Labor
Parts
Total
Total
$30,000.00
$202.80
$30,202.80
4.2 Schedule
Week
Task
Write proposal
9/14
Finalize proposal
Research and select parts and sensors
9/21
Build the harp frame
Test lasers and make plan to improve power supply
9/28
Test functionality of lasers on the harp frame
Test photoresistor data and build photoresistor circuit
10/05
Validate the design and connect photoresistor to MCU
Design the layout of USDS
10/12
Test angles and corner cases of USDS
Design the PCB of microcontroller using EAGLE
10/19
Validate the design
Test the functionality of accelerator
10/26
Test acceleration data and map data to MIDI velocity
values
Combine all components and test device functionality
11/02
Revise the PCB design
Prepare mock demo
11/09
Prepare presentation
Prepare final paper
11/16
Final revision of PCB
11/23
11/30
12/07
Responsibility
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
Thanksgiving Break
Prepare presentation
Prepare presentation
Check in supplies
Finish final paper
Hanze Tu
Yingxi Hai
Hanze Tu
Yingxi Hai
8