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Monthly Archives: March 2012

My new component arrived this morning and i have been testing it and establishing its peramiters and requirements.

Initially i have just hooked the accelerometer straight up to the arduino simply to test all is working fine but this will eventually be done with capasitors to limit the band width and reduce any noise. I used the following code retrieved from this web site http://arduino.cc/en/Tutorial/ADXL3xx

Accelerometer test

Using the data sheet i have calculated that using 0.47uf capasitors on each output will give an approximate band width of 10Hz

I’ve sketched out a diagram of the circuit i will use for the final piece which i also intend to draw up on Multisim to give a clear idea of whats going on which should be posted next week.

Ordered a 12 month student liecence for Max 6.0 today as i feel that being able to work with Max MSP and Pro tools at home will improve the quality and complexity of the final piece.  This cost a total of $60 which is about £37.

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After a troublesome day i have discovered that the Digital Accelerometer i have is proving to be more compicated than first expected. After further research into the area i have discovered more support material available for anaolog accelerometers and in particular the Triple Axis Accelerometer Breakout – ADXL335

and the help page i have found most useful

http://arduino.cc/en/Tutorial/ADXL3xx

This is the new component i have ordered from CoolComponents.com at a cost of £22.50 with the accompanying datasheet below.

adxl335

Until this arrives i will concentrate on the software i will be using, Maxuino and either ProTools or Ableton Live (whichever had the better capabilites i require.

I need to test each of the sensors to ensure they work and their thresholds ie. voltage and Arduino serial data.

Here is the Arduino code i found to help me test the flex sensor

Doc1FlexTest

and using the following Voltage Divider where R1 = Flex Sensor (25 – 45Kohm), and R2 = 22kohm resistor

and using the following formula, calculated that the voltage should vary from approx 2.34v and 1.64v when Vin = 5v

and using the serial monitor in the arduino sorfware noted that the data varied from 260 when the sensor was straight to 130 when the sensor was bent.

A rough test showing that the sensor worked.  The same was repeated with all 6 sensor to ensure no defects.

After considering which sensors would be most appropriate for the types of hand gestures i i want to use i have decided on Flex Sensors and Accelerometers.  These have been purchased from proto-pic.com at a total cost of £61.20 for

2 Triple Axis Acceletometer Breakout – MMA8452Q

Features

• 1.95 V to 3.6 V supply voltage

• 1.6 V to 3.6 V interface voltage

• ±2g/±4g/±8g dynamically selectable full-scale

• Output Data Rates (ODR) from 1.56 Hz to 800 Hz

• 99μg/Hz noise

• 12-bit and 8-bit digital output

• I2C digital output interface (operates to 2.25 MHz with 4.7 kΩ pullup)

• Two programmable interrupt pins for six interrupt sources

• Three embedded channels of motion detection

– Freefall or Motion Detection: 1 channel

– Pulse Detection: 1 channel

– Jolt Detection: 1 channel

• Orientation (Portrait/Landscape) detection with set hysteresis

• Automatic ODR change for Auto-WAKE and return to SLEEP

• High Pass Filter Data available real-time

• Self-Test

• RoHS compliant

• Current Consumption: 6 μA – 165 μA

6 Flex Sensor 2.2″

Features

– Angle Displacement Measurement

– Bends and Flexes physically with motion device

– Possible Uses

– Robotics

– Gaming (Virtual Motion)

– Medical Devices

– Computer Peripherals

– Musical Instruments

– Physical Therapy

– Simple Construction

– Low Profile

– Flat Resistance: 25K Ohms

-Resistance Tolerance: ±30%

-Bend Resistance Range: 45K to 125K Ohms (depending on bend radius)

-Power Rating : 0.50 Watts continuous. 1 Watt Peak

-Temperature Range: -35°C to +80°C

Data Sheets

accel_MMA8452Q

flex22

I have been investigating Sensor types that would work well with my intended project.

For my previous project i had used Piezoelectric sensors on the tips of each finger of a glove.  The principle of a piezoelectric sensor is that under pressure it produces a voltage.  With my previous project i found that these sensors were unreliable and had a short life-span due to their fragile design.  I had the task of researching the sensors that were available and thier suitablilty for my final project.

Sensors that are commonly used in musical applications and their characteristics are as follows (Information gathered from the book New Digital Musical Instruments)

Force-Sensitive Resistors.   Typically made up of a conductive polymer film sensor whose conductance is proportional to the applied force; electrical resistance will decrease with the increase of pressure applied to the device.

http://www.ladyada.net/learn/sensors/fsr.html

http://at.or.at/hans/misc/itp/pcomp/fsr.html

http://www.adafruit.com/blog/2009/05/20/force-sensitive-resistors-are-for-squeezing-massive-tutorial-and-theyre-in-stock/

Strain Gauges. Resistive elastic sensors whose resistance is a function of applied strain due to mechanical stress.  Their resistance decreases with compression and increase with tension.    Strain Gauges are more accurate than Force Sensitive Resistors and noramlly used for sensing weight,

http://www.eidactics.com/Downloads/Refs-Methods/NI_Strain_Gauge_tutorial.pdf

http://zone.ni.com/devzone/cda/tut/p/id/3642

http://www.kyowa-ei.co.jp/english/products/gages/pdf/howsgw.pdf

http://www.radio-electronics.com/info/t_and_m/data-acquisition/strain-gauge.php

Bend/Flex Sensors Consisting of a strip of plastic with conductive ink, bending the sensor causes its resistance to increase.  Bend sensors are very useful because they can be easily attached to body parts or textiles

http://devices.sapp.org/component/flex/

http://itp.nyu.edu/physcomp/Labs/AnalogIn

http://www.ecs.umass.edu/ece/m5/tutorials/CdS_Flex_Sensor.html

http://devices.sapp.org/device/flex/

http://protolab.pbworks.com/w/page/19403657/TutorialSensors

Infrared SensorsBased on the measurement of properties of light signals

http://elecrom.wordpress.com/2008/02/19/how-to-make-simple-infrared-sensor-modules/

http://www.pages.drexel.edu/~pyc23/ir_sensor.html

Accelerometers Measures linear acceleration in one or more axes and can also sense inclination.  Also useful for measuring shock.

http://0110.be/artikels/lees/The_Pidato_Experiment%253A_Vibrato_on_a_Digital_Piano_Using_an_Arduino

http://www.dimensionengineering.com/accelerometers.htm

http://www.omega.co.uk/prodinfo/accelerometers.html

http://arduino.cc/en/Tutorial/ADXL3xx

http://arduino.cc/en/Tutorial/Memsic2125?from=Tutorial.AccelerometerMemsic2125

The first task was to research the products already available in the current marketplace and where research was being undertaken in this area.  This was a field i was already very familiar with as i had undertaken research for a physical computing project earlier in the year.  Below are several links to products or research i found that was relevent to my proposed project

Commercial Examples

http://www.vrealities.com/glove.html – an american site with a collection of commercial Data gloves using bend sensors and pitch-and-roll sensors ranging between $600 for a single glove and $1400 for a pair.

http://www.technologyreview.com/computing/22838/ – shows a review of an open-source data glove using accelerometers in each finger to register independent movement at a cost of $499 for one glove.

http://www.cyberglovesystems.com/ – a company specialising in advanced data gloves using up to 22 sensors to capture even the slightest hand of finger movement.  No prices given.

http://www.psymbiote.org/glove.html – shows a prototype of a data glove using flex sensors but as stated on the website it remains a work in progress but visually differs from the previous examples as this has been designed with a unique and interesting appearance and is described as Hybrid Apparatus for Social Interface.

http://www.cwonline.com/store/view_product.asp?Product=1179 – a data gloved designed for 3D games and virtual environments at only $59 using flex and sensors and accelerometer

http://www.musicradar.com/news/drums/musical-glove-concept-makes-idle-tapping-worthwhile-182267 – shows a concept of a glove designed for the user to idly tap out beats with their fingers.  As only a concept to technical detail or cost available.

http://www.musicradar.com/news/tech/piano-hands-gloves-let-you-play-anywhere-175027 – Piano Gloves which use sensors on each finger that when stuck on a flat surface produce piano notes at a cost of £50.

Below are some examples of projects people have undertaken

http://www.tufts.edu/programs/mma/emid/projectreportsS04/kriete.html

http://createdigitalmusic.com/2005/08/hypersense-complex-gestural-gloves-for-music/

http://www.instructables.com/id/How-to-create-simple-animatronics-using-the-MAKE-c/step4/Electronics-flex-sensors-and-lights/

http://benkrasnow.blogspot.com/2010/12/diy-10-finger-flex-sensor-gloves-for.html

http://hackedgadgets.com/2006/05/19/top-5-diy-glove-keyboards/

http://news.cnet.com/8301-17938_105-20032087-1.html

http://www.instructables.com/id/SNF-Drumming-MIDI-Glove-using-Arduino-and-light-se/

Below are some links to video clips showing different attempts by people to great music with different types of data glove.

http://www.youtube.com/watch?v=1THRgjkKyg8

http://www.youtube.com/watch?v=k0-oMOJKERE&feature=related

http://www.youtube.com/watch?v=OTovkPxXOQk&feature=related

http://www.youtube.com/watch?v=x17TcUMD20E&feature=related

http://www.youtube.com/watch?v=6ApPgC_Idjs&feature=related

Below is a list of books and articles that all feature data gloves or cover relevent technologies

New Digital Musical Instruments: Control and Interaction Beyond the Keyboard. Miranda & Wanderley2006.

Physical Computing: Sensing and controlling the physical world with computers. O’Sullivan and Igoe. 2004.

Transducer Interfacing Handbook. Sheingold. 1981.

Getting Started with Adruino. Banzi. 2009.