Block 3 - Unit 2: Choosing interaction devices Flashcards Preview

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Interaction devices. (3 comments)

One assumption easily made is the kind of interaction devices used - focus often on keyboard / mouse.

Should consider particular requirements, and how best met by various devices.

We want to achieve something - choice of device is crucial to how well we can achieve these goals.


3 categories of input devices.

1. Keyboards, keypads and buttons.

2. Pointin devices.

3. Tags and sensors.


Discrete input devices.

Used to enter discrete data, such as letters, numbers or commands.

Not suited to continuous tasks like dragging icons.


Variations on standard keyboard. (4)

Big keys - context allows redundant keys to be excluded.

Chord keyboard - limited space or keeping other hand free.

Keypad - may be more appropriate if full range of alphanumeric keys not needed (eg. calculators, phones).

Individual buttons - even simpler (eg. heating controls, burglar alarm).


Factors in choosing discrete input device. (3)

Shape - split to help reduce RSI.

Key size - portability, impairment.

Robust - some environments can get dirty / liquid. Membrane keyboards are sealed, but lack feedback.


Continuous input devices.

Good at tasks that can't easily be split into discrete steps, eg. drawing sketches.

Works well in combination with a keyboard (discrete).


Types of pointing device. (2)

Indirect pointing devices - user moves cursor with secondary device.

Direct pointing devices - can be pointed directly at the screen.


Types of indirect pointing devices. (4)


- Displacement joystick - lever moves in 2D
- Isometric joystick - lever is rigid, and pressure on it is translated into movement.

Trackball - 'inverted mouse' - some people with limited movement find it easier.

Graphics tablet - cursor moves as user moves finger / stylus. Eg. for drawing - more conventional.


Types of direct pointing device. (2)


Pen system - touch-screen set up for using as stylus - can have smaller targets. Eg. signing for delivery, portable game computer.


Factors in choosing the right pointing device. (6)

How easy to learn does in need to be?

How accurate does the device need to be?

How much time users spend using product?

How much space?

How robust?

How dexterous is the user?


Tags and sensors.

Allow info from the physical world to be captured for use in an interactive product.



Used to attach static info to physical objects.

May be active or passive.

RFID tags - eg. track goods; reader doesn't need to be in close proximity.



Can monitor environment and transmit changing data.
Light, heat, movement, etc.

Pressure and movement good for games.
WiiMote - pointer and motion sensor.


Factors when choosing a sensor. (4)

- Characteristics of phenomenon being sensed:
Threshold, range and sampling rate.

- Characteristics of environment being sensed:
Sensor fixed or moving? Waterproof? Robust?

- Appropriate physical characteristics:
Own power source? How big?

- Level of functional complexity required:
Can simply report a single piece of data, or more sophisticated functions.
Can also operate alone or as part of a wider collaborative network.


Alternative approaches to input. (3)

Eye tracking:
Can move cursor, and press by blinking or staring at a button.

Iris and fingerprint recognition:
Where security is important, eg. ATM, secure buildings.

Handwriting recognition:
Increased with popularity of handheld computers.
System needs to learn each individual's writing.
Most require letter to be formed individually, and some requirme specific strokes - makes it slow.


3 categories of output devices.



Simple output devices (lights, dials, buzzers).



Can represent a wide variety of visual elements.

Even those with visual impairments like to use them if possible, eg. magnifiers / zoom software.

LCDs - small, thin and light; low power.


Choosing the right screen. (5 factors)

How detailed image?:
Resolution - amount of detail represented in number of pixels.
Manipulating pictures - high; text - low ok.

Number of colours?

How large?:
Low prices - users tend to user larger screens; more info displayed and larger text; eg. graphic designers.

Size, weight and power requirements

Important in crowded offices - flat screens.


Loudspeakers and headphones.

Most interactive devices have sound - speech, music sound effects.
Many have microphones ('matching' input device).

How will they be used?
Composer - high quality.
Sound effects only - can be lower quality.

If possible, should be tried in environment.


Simple output devices.

Most common - lights, dials and buzzers; cheap and very useful.
Vibration also used.


Examples of simple output devices. (4)

On/off, charging, network reception.

7-segment displays - numbers and letters.

Dials / guages / indicate levels, eg. speedo, battery level.

Sound - eg. buzzer - attracts attention, eg. next stage on a breadmaker.

Common to combine these - eg. microwave - multiple outputs to indicate when finished.


What to consider when selecting simple output devices.

Is data represented more effectively in analogue or digital.
Discrete data - data that has a finite number of states, steps or increments. Eg. single light, numbers or letters - can be represented by binary digits.

Analogue data - can be represented by a dial or gauge, eg. pressure, temperature.

Persistence of output should be considered, eg. printer output longer lasting than a screens.


Alternative approaches to output. (2)

Head-up displays - key info is projected in line of sight, apparently just in front of the windscreen.
(Form of augmented reality).

Stereoscopic displays - creates 3D effect by using 2 screens, one in front of each eye.