Hands-On MaterialFrom National Instruments

Introduction to LabVIEWElectrical Wiring

Music Instrument

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Course Goals Become comfortable with the LabVIEW

environment and data flow execution Ability to use LabVIEW to integrate HW/SW and

create your personal music instrument. LabVIEW Concepts

Find and use math and complex analysis functions Work with data types, such as Boolean, integer, and Displaying

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Music Instrument Project

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Pitch / Gain

LabVIEW Graphical Development System Graphical Programming Environment Compile code for multiple OS and devices Useful in a broad range of applications

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The NI Approach – Integrated Hardware Platforms

High-SpeedDigitizers

High-ResolutionDigitizers and DMMs

Multifunction Data Acquisition

DynamicSignal Acquisition

Digital I/OInstrumentControl

Counter/Timers

MachineVision

Motion Control

Distributed I/O andEmbedded Control

Laptop PC PDADesktop PCPXI Modular Instrumentation

Signal Conditioningand Switching

Unit Under Test

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Section I – LabVIEW Environment

A. Getting Data into your Computer• Data Acquisition Devices

– NI-DAQ– Simulated Data Acquisition– Sound Card

B. LabVIEW Environment• Front Panel / Block Diagram• Toolbar /Tools Palette

C. Components of a LabVIEW Application• Creating a VI• Data Flow Execution

D. Additional Help• Finding Functions• Tips for Working in LabVIEW

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A. Setting Up Your Hardware

Data Acquisition Device (DAQ) Actual USB, PCI, or PXI Device Configured in MAX

Simulated Data Acquisition Device (DAQ) Software simulated at the driver level Configured in MAX

Sound Card Built into most computers

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What type of device should I use?

Sound Card* NI USB DAQ NI PCI DAQ Instruments*AI Bandwidth 8–44 KS/s 10–200 KS/s 250 K–1.2 Ms/s 20kS/s–2 GS/sAccuracy 12–16 bit 12–16 bit 14–18 bit 12–24 bitPortable x x — someAI Channels 2 8–16 16–80 2AO Channels 2 1–2 2–4 0AC or DC AC AC/DC AC/DC AC/DCTriggering — x x x

Calibrated — x x x

* The above table may not be representative of all device variations that exist in each categoryENGR 100 Section C

What is MAX?

MAX stands for Measurement & Automation Explorer. MAX configures and organizes all your National

Instruments DAQ, PCI/PXI instruments, GPIB, IMAQ, IVI, Motion, VISA, and VXI devices.

Used for configuring and testing devices.

Icon Found on

Windows Desktop

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Exercise 1 – Setting Up Your Device

Use Measurement and Automation Explorer (MAX) to: Configure and test your Simulated Data

Acquisition (DAQ) device

Track B

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Start»All Programs»National Instruments LabVIEW 8.6

Startup Screen:

Start from a Blank VI:

New»Blank VI

Start from an Example:Examples»Find

Examples…

»

or

Open and Run LabVIEW

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Each VI has 2 Windows

Front Panel• User Interface (UI)

– Controls = Inputs– Indicators = Outputs

Block Diagram• Graphical Code

– Data travels on wires from controls through functions to indicators

– Blocks execute by Dataflow

LabVIEW Programs Are Called Virtual Instruments (VIs)

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Controls Palette(Controls & Indicators)

(Place items on the Front Panel Window)

Indicator:Numeric Slide

Control:Numeric

Customize Palette View

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Functions (and Structures) Palette(Place items on the

Block Diagram Window)

Structure:While Loop

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• Recommended: Automatic Selection Tool• Tools to operate and modify both front panel and

block diagram objects

Operating Tool

Positioning/Resizing Tool

Labeling Tool

Wiring Tool

Tools Palette

Automatic Selection Tool

Automatically chooses among the following tools:

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Run Button

Continuous Run Button

Abort Execution

Execution Highlighting Button

Additional Buttons on the Diagram Toolbar

Status Toolbar

Retain Wire Values Button

Step Function Buttons

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Block Diagram Window

Front Panel Window

Demonstration 1: Creating a VI

InputTerminals

OutputTerminal

BooleanControl

GraphIndicator

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• Block diagram execution– Dependent on the flow of data– Block diagram does NOT execute

left to right• Node executes when data is

available to ALL input terminals• Nodes supply data to all output

terminals when done

Dataflow Programming

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Debugging Techniques• Finding Errors

• Execution Highlighting

• Probes

Click on broken Run button.Window showing error appears.

Click on Execution Highlighting button; data flow is animated using bubbles. Values are displayed on wires.

Right-click on wire to display probe and it shows data as it flows through wire segment.

You can also select Probe tool from Tools palette and click on wire.

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Context Help Window Help»Show Context Help, press the

<Ctrl+H> keys Hover cursor over object to update window

Additional Help–Right-Click on the VI icon and

choose Help, or–Choose “Detailed Help.” on

the context help window

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Tips for Working in LabVIEW Keystroke Shortcuts

<Ctrl+H> – Activate/Deactivate Context Help Window <Ctrl+B> – Remove Broken Wires From Block Diagram <Ctrl+E> – Toggle Between Front Panel and Block

Diagram <Ctrl+Z> – Undo (Also in Edit Menu)

Tools»Options… – Set Preferences in LabVIEW VI Properties–Configure VI Appearance,

Documentation, etc.

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Section II – Elements of Typical Programs

A. Loops• While Loop• For Loop

B. Functions and SubVIs• Types of Functions• Creating Custom Functions (SubVI)• Functions Palette & Searching

C. Decision Making and File IO• Case Structure• Select (simple If statement)• File I/O

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Loops While Loops

i terminal counts iteration Always runs at least once Runs until stop condition is

met

•For Loops– i terminal counts iterations– Run according to input N of

count terminal

While Loop

For Loop

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Drawing a Loop

1. Select the structure

2. Enclose code to be repeated

3. Drop or drag additional nodes and then wire

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3 Types of Functions (from the Functions Palette)

Express VIs: interactive VIs with configurable dialog page (blue border)

Standard VIs: modularized VIs customized by wiring (customizable)

Functions: fundamental operating elements of LabVIEW; no front panel or block diagram (yellow)

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What Types of Functions are Available?

Input and Output Signal and Data Simulation Acquire and Generate Real Signals with DAQ Instrument I/O Assistant (Serial & GPIB) ActiveX for communication with other programs

Analysis Signal Processing Statistics Advanced Math and Formulas Continuous Time Solver

Storage File I/O

Express Functions Palette

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Searching for Controls, VIs, and Functions

• Palettes are filled with hundreds of VIs

• Press the search button to index the all VIs for text searching

• Click and drag an item from the search window to the block diagram

• Double-click an item to open the owning palette

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Create SubVI

Enclose area to be converted into a subVI.

Select Edit»Create SubVI from the Edit Menu.

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LabVIEW Functions and SubVIs operate like Functions in other languages

Function Pseudo Codefunction average (in1, in2, out){out = (in1 + in2)/2.0;}

SubVI Block Diagram

Calling Program Pseudo Codemain{average (in1, in2, pointavg)}

Calling VI Block Diagram

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Connector Pane and Icon Viewer

Use this connector pane layout as a standard

Top terminals are usually reserved for file paths and references, such as a file reference

Bottom terminals are usually reserved for error clusters

Icon Viewer – Create an Icon Create custom icons by right-clicking the icon

in the upper-right corner of the front panel or block diagram and selecting Edit Icon or by double-clicking the icon

You also can drag a graphic from anywhere in your file system and drop it on the icon

Refer to the Icon Art Glossary at ni.com for standard graphics to use in a VI icon

Exercise 3.1 – Analysis Track A,B,&C

•Use LabVIEW Express VIs to:–Simulate a signal and display its amplitude and frequency

This exercise should

take 15 minutes.

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How Do I Make Decisions in LabVIEW?1. Case Structures

2. Select

(a) Boolean (b) Numeric

(d)

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(c) string

Case structure

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Homework Practice Problem 1

Create the required VI(s) to achieve the following tasks.

Requirements:1. Create a basic calculator function with the ability to add, subtract, multiply,

and divide two numbers and display the output2. Allow the program to keep on running until a stop button is pressed.

File I/OFile I/O – passing data to and from files Files can be binary, text, or spreadsheet Write/Read LabVIEW Measurements file (*.lvm)

Writing to LVM file Reading from LVM file

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spreadsheet-formatted files

File I/O Programming Model – Under the Hood

Open/Create/

Replace File

Read and/or

Write to File

Close File

Check forErrors

File I/O>>Write to Spreadsheet File

Section III – Presenting your Results

A. Displaying Data on the Front Panel• Controls and Indicators• Graphs and Charts• Loop Timing

B. Signal Processing• MathScript• Arrays• Clusters• Waveforms

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What Types of Controls and Indicators are Available?

Numeric Data Number input and display Analog Sliders, Dials, and

Gauges Boolean Data

Buttons and LEDs Array & Matrix Data

Numeric Display Chart Graph XY Graph Intensity Graph 3D graph: point, surface,

and model Decorations

Tab Control Arrows

Other Strings and text boxes Picture/Image Display ActiveX Controls

Express Controls Palette

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Charts – Add 1 data point at a time with history

Waveform chart – special numeric indicator that can display a history of values

Chart updates with each individual point it receives

Functions»Express»Graph Indicators»Chart

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Graphs – Display many data points at once

Waveform graph – special numeric indicator that displays an array of data

• Graph updates after all points have been collected• May be used in a loop if VI collects buffers of data

Functions»Express»Graph Indicators»Graph

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Graph and Chart (history length)

Homework Practice Problem 2

Requirements:1. Create a VI which runs exactly 50 times or

until a stop button is pushed2. At each intervals, it generates a random

number between 50 and 100.3. Display the random number on a

waveform chart.

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Shift registers (Moving Average)

Homework Practice Problem 3

Requirements:1. Modify the Previous Practice Problem so

that the total sum of all the random numbers generated is displayed

2. Using another shift register to have moving average of three numbers

3. Plot moving average and original random number in the waveform chart , i.e. two curves in one chart. (Hint: use “bundle” in cluster pallets

• Loops can accumulate arrays at their boundaries with auto-indexing

• For Loops auto-index by default

• While Loops output only the final value by default

• Right-click tunnel and enable/disable auto-indexing

Building Arrays with Loops (Auto-Indexing)

Wire becomes thicker

Wire remains the same size

Auto-Indexing Disabled

Auto-Indexing Enabled

Only one value (last iteration) is passed out of the loop

1D Array

0 1 2 3 4 5

5

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Creating an Array (Step 1 of 2)From the Controls»Modern»Array, Matrix, and Cluster subpalette, select the Array icon.

Drop it on the Front Panel.

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Create an Array (Step 2 of 2)1. Place an Array Shell.

2. Insert datatype into the shell (i.e. Numeric Control).

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Practice:2D array?

Array

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Homework Practice Problem 4

Requirements:1. Generate an array of 20 random numbers.2. Find the maximum, minimum, and mean

of the array using a shift register.3. Modify the array by multiplying the fifth

element by 5

How Do I Time a Loop?1. Loop Time Delay

• Configure the Time Delay Express VI for seconds to wait each iteration of the loop (works on For and While loops).

2. Timed Loops Configure special timed While loop for desired dt.

Timed LoopTime Delay

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Control & Indicator Properties

Properties are characteristics or qualities about an object

Properties can be found by right clicking on a Control or Indicator• Properties Include:

– Size– Color– Plot Style– Plot color

• Features include:– Cursors– Scaling

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Math with the MathScript Node Implement equations and algorithms textually Input and Output variables created at the border Generally compatible with popular m-file script language Terminate statements with a semicolon to disable immediate

output

Prototype your equations in the interactive MathScript Window.

(Functions»Programming»Structures»MathScript)

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The Interactive MathScript Window Rapidly develop and test algorithms

(LabVIEW»Tools»MathScript Window)

OutputWindow

VariableWorkspace

View/ModifyVariable Contents

User Commands

m-file Script

•Share Scripts and Variables with the Node

•View /Modify Variable content in 1D, 2D, and 3D

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Formula Node Practice

Homework Practice Problem 5

Requirements:1. Create a formula node which has 3 inputs(X, Y, Z) and one output. If X>Y

output Z, otherwise output 0.2. Create a subVI which performs the same task as the formula node. (Hint: Use

the selection function found in the comparison palette)

Structure>>formula node

Review of Data Types Found in LabVIEW

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DAQ

Real World

Signal

Pressure,Temperature,

Distance,Light

Sensors

Signal ConditioningVoltage

Current

A/DConvertor

D/AConvertor

Power Amp

Transducer

Digital World

Signal Processing

DAQ Practice

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DAQ Assistant Express VIConti Acq&Graph Voltage int Clk.vi

Homework Practice Problem 6

Requirements:1. Create a data acquisition task which reads

data from the audio input on your MyDAQ using the low level DAQmx functions

2. Display the signal on a waveform chart3. After collecting this data write it to a

comma separated file using the Read From Measurement File express VI.

MyDAQ

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USB Cable

20-Position Screw Terminal Connector

Audio Cable

DMM Banana Cable

MyDAQ

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Soft Front Panel (SFP)

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Fun Generator

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D I/O

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MyDAQ

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1. Create an audio loopback program using the MyDAQ. Read the signal from audio in port and output it to the audio out port. Stop the loop when a user pushes a stop button

2. Display the acquired signal on a graph.

2V

State Machines

1. While Loop2. Shift Register3. Case Structure

State Machines Transitions

• Several programming techniques exist for transitioning from state to state in LabVIEW using state machines

• Default transition implies that after one state, another state always follows

• Transitions between two potential states can be handled by a select function

State Machine

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Homework Practice Problem 7

Vending Machine (15 cents Gum):1. Create a state machine driven program which follows the following state diagram2. Send user message via Display monitor at each state. (Hint: totally 5 states and 2

transition conditions)

Insert Change Insert 10 Cents Insert 5 Cents Collect Gum Collect Gum/Change

Communicating between Loops• Communicating between loops using data flow is not possible

• The left loop executes completely before the right loop

• Variables are needed when communication with wires does not give the desired behavior

Local Variables

• Local Variables allow data to be passed between parallel loops.

• A single control or indicator can be read or written to from more than one location in the program

– Local Variables break the dataflow paradigm and should be used sparingly

Creating a Local Variable - Walk Through

In this example we will see how Local Variables allow us to share data between parallel loops. We will create a program that toggles two separate LEDs using one switch. It also stops two loops with one button.

Create the block diagram and front panel show in the notes.

Creating Local Variables

Right-click on the Stop Button in the Front Panel and change the Mechanical Action to “Switch When Released” since Local Variables cannot store Latched data.

Producer/Consumer Design Pattern

SwitchLE

VITI

ON

LEVI

TIO

N

LEVI

TIO

N

3-Way Switch 4-Way Switch2-Way Switch

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Single 2-Way Switch Layout

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3-3 Switch Layout

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3-4-3 Switch Layout

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Logic Gate

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Logic Gate

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Logic Gate

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Logic Gate

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Music Instrument Project

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Pitch / Gain

Digital I/O Hysteresis

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Analog signal Vin(t)

Digital signal01011…

Pull down resistor

+5v

Contact bounce

Equal temperament

Fnm=f0*2^((n/12)+m-4) The vast majority of Western

music is based on the tuning system called equal temperament in which the octave interval (a 2:1 ratio in frequency) is equally subdivided into 12 subintervals called semitones.

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A4 Concert A 440Hz(m=4,n=0)

C4

Octave

A5 880Hz(m=4,n=12)or(m=5,n=0)

Sine Wave VI

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Play music via Laptop audio chipUsing “Play Waveform” Express VI Graph & Sound>>Sound>>Output>>Play

Waveform Signal Process>>Sig Generation>>Sine Wave Waveform>>Build Waveform

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Play music Using low level Sound output VI Graphics&

Sound>>Sound>>Output>>Configure Graphics& Sound>>Sound>>Output>>Write Graphics& Sound>>Sound>>Output>>Clear Signal Process>>Signal Generation>>Sine

Wave

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Play music

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Homework Practice Problem 8

Procedure: Create the required VI(s) to play sound at certain freq.

Requirements:1. Modify the play music using express vi with Sampling Frequency

(=44.1kHz), A4 Concert Frequency (f0=440 Hz), Duration(=0.1s) , Frequency fnm (=f0*2^((n/12)+m-4)), numeric control n (integer 0~12), m(integer 0~12)

2. Add a while loop and shift register so that the sound will be played when the value of frequency fnm is changed.

Simple Read /Write .wav Files

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Graphics& Sound>>Sound>>Files>>Simple ReadGraphics& Sound>>Sound>>Files>>Simple WriteGraphics& Sound>>Sound>>Files>>Info

Create 2 channel wave file Signal Processing>>Signal Generation>> Sine Wave Signal Processing>>Signal Generation>> Uniform Noise Signal Processing>>Signal Generation >>Quick scale

(Scale audio signal to +/- 1 range before saving to a .wav file)

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Free wave editor tool: Audacity

Property and Invoke Nodes

• Create Property and Invoke nodes for a VI element by right-clicking the element and selecting Create»Property Node.

• Use the Property Node to get and set object properties.

• Invoke object methods with the Invoke Node.

Play music file using ActiveX Windows media player

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Property Nodes WMPLib.IWMPPlayer4

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(File location, Controls)

Invoke NodeInvoke Method of controls (Play, Pause)

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Invoke NodeInvoke Method of WMPLib.IWMPPlayer4

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(Close WMPlayer)

Close Active X reference

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Example (Play, Pause two music files)

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Music Instrument Switch (Digital) Key board

Play with Hand/Pam/Foot/ Whole Body?

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DI0DI1

DI2

DI3DI4DI5

.

.

.5V DC

Music Instrument Switch (Analog) Voltage /Current Variation

Capacitance Variation Inductance Variation Resistance Variation(Potentiometer)

Distance Variation Acoustic Sensor

Microphone Optical Sensor (Photo-Diode + Opamp)

Optical Theremin

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