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Hardware review.

We worked very closely on every area of the project together, we divided the responsibilities in to four main sections that covered the four major areas of the project; content, hardware, software, and design. My responsibilities were hardware and content.

During the course of this project we built three multi-touch devices in total. I was responsible for researching, sourcing and purchasing all the materials, tools and electronic equipment necessary to construct each individual device.

Alpha Prototype (MT Mini)
Our first prototype multi-touch device was built using very simple and basic components. We organised and purchased all the necessary materials which included a cardboard box, a picture frame with glass and a Targus webcam, which we bought in Soundstore in Togher, Cork.

Beta Prototype
We started this project with no tools, materials or electronic equipment, everything had to be bought excluding our laptops. The first major step when designing the Alpha Prototype was choosing a suitable projector.

Projector

The projector had a great influence on the overall dimensions of the prototype as we had to consider the ‘throw’ of the projection and the resulting ‘projected’ screen size. For usability purposes we did not want a viewing screen thats too small or a table thats too high. After researching many options we chose the BenQ MP771 projector as it was within our price
range and met all the necessary specifications. The projector was not available in Ireland so we had to order it from Poland. Unfortunately, when it arrived from Poland it was not functioning properly so we had to return it and order another from the UK.

Fortunately our second projector worked perfectly and we got the projection necessary to start constructing the table.

Tools and Materials
We had no tools beginning this project so we had to buy everything we needed. To keep things simple we made a list and bought everything in Woodies, the items we needed included;
• Cordless drill
• Saw
• Hammer
• Spirit level
• screws and nails
• screwdriver set
• protractor & ruler
• Measuring tape
• Sandpaper
• Stanley knife
• Black paint and white undercoat paint.
• Paint tray, rollers and brushes
• No more nails (unibond wood glue)
• Chipboard and plywood for the base and walls
• Pine timber for the frames.

Webcam
We purchased three different webcams during the course of this project. The first was a Targus webcam that we damaged trying to remove the IR filter. The second webcam we bought was a Microsoft VX1000. This camera worked OK but was not perfect for this project as the field of view was too narrow and the frame rate was too slow for blob detection. More research led me to the
Sony PS3 eye which met all the specifications we desired, we just had to remove the IR filter and replace it with a bandwidth filter.

Diffuser

We looked at purchasing many different diffuser materials for the screen surface including Rosco grey and Lee filters. For testing purposes we bought a roll of tracing paper which worked out perfectly for the second Prototype. For the final prototype we used a 225 Lee Filter which we got from Kevin O Mahony, a masters student in CIT, the Lee filter gave us better blob recognition and also a more professional and ‘screen like’ appearance.

Touch Surface

In the early stages of the project we still has yet to decide between the DI and FTIR multi-touch systems. When looking at purchasing a touch surface for the multi-touch table we bought acrylic as it worked well with both systems We eventually chose the DI set up. We bought the Acrylic from Blarney Plastic Specialists in Ballincollig for the first prototype. We opted to use glass instead of acrylic for the final prototype.

IR illuminators

There was many variables to consider when buying IR illuminators including the power of the light, the number of diodes and the wavelength. The type of IR illuminators we needed for this project were not available in Ireland so we had to search online, eventually we bought two 148 boards from Hong Kong on E-bay.

Unfortunately our LED lights arrived with no power supply so we picked up a switched Mode AC to DC adaptor in Maplin Electronics. We also bought a pack of 5 amp terminal blocks to connect the LED lights to the power supply. It was a fairly straight forward procedure connecting and powering up the two boards which we ran at 12 volts.

Reflective surface

To create even light from the IR illuminators on the projection screen we had to consider bouncing light from the inside walls of the table as opposed to pointing them directly at the table, for testing purposes we bought aluminum foil which worked perfectly for us.

Fans
As the projector is essentially incased in a box it can get very warm inside so it is necessary to keep it cool to function correctly. We bought two 12 volt Bi sonic fans in Maplin Electronics for this purpose. We chose this particular model because we could hook it up to the same power supply as the IR illuminators. These fans were extremely loud at 60 decibels so we had to return them and purchase the quietest fans we could get, which were the Asaka Ultra Quiet 120 mm.

Laptop connector
We had to buy an Apple Mini-DVI to DVI Adapter to connect our laptops to the projector. We bought it in AT Mac, Penrose Quay Cork.

Picture frame & cardboard box
We needed a picture frame and a cardboard box to create our first prototype MT mini. We picked up a picture frame in Dunnes Stores and a card board box in Centra in Riverstick.

Bandpass filter

To convert the Sony PS3 eye webcam into a multi-touch camera we needed to remove the IR filter and replace it with a bandpass filter. For testing purpose we created our own bandpass filter from exposed 35 mm negative film and fortunately it worked perfectly.

Speakers
When purchasing speakers we had to consider the shape, watts and the option of a built in amplifier. We used Creative I-Trigue 2300 2.0 stereo speakers form Argos for audio feedback and video sound, which work perfectly.



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