Chapter 8: Design Decision

Factor Of Safety
The use of one of more element to prevent system malfunction. It is to offset the effect of unknown variable.

Example: Milok Ion

Figure 8

The figure above show the image of iron. The iron has safety that will control the heat volume. It is important to avoid of charred clothing if the volume not fixed. The controller also have provided label to make user easy to know the level of heat. If the system are damaged, the ion cannot produce the heat.

Satisficing
A principle which proposed that a design that satisfy the basic needs is more preferable.

Example: Water Heater

Figure 8.1

The figure above show  water heater. It satisfy the user need as they can choose either to use hot water of cold water to bath by pressing the button( in red square mark) instead. 

Redundancy

Method to prevent the system from malfunction. This can be achieve by adding of more elements that’s necessary to maintain the performance of a system. There are 4 type of redundancy:

Diverse Redundancy

The use of different types of elements to avoid system from failure

Example: Reset button of Samsung Galaxy S4

Figure 8.3: Two different type of reset button

The presence of two reset button in Samsung Galaxy S4 is the example of diverse redundancy. Usually, when user want to reset the phone, they need to go into the setting, and head to the back up system and choose the factory data reset ( shown in image with red circle). But the things happen when sometimes your phone is completely locked up and you can’t even access the menus since swiping the phone’s screen would not cause any effect. Therefore, another way to reset the phone is through manually pressing the reset button located outside the phone ( shown in image with red arrow pointing the button) .

Homogenous Redundancy

The use of single type elements to avoid system from failure. the failure of an elements will affect the performance of the system , but the whole system still function-able

Example: Umbrella's Rib

 Figure 8.3.1 

Umbrella is design with the presence of many ribs. The ribs holds the shape of the umbrella when the umbrella is being opened. The presence of ribs is to hold the shape of an umbrella, thus preventing the user from getting wet or exposed to sunlight. When one of the rib is broken, the shape will be change. Although the umbrella still can be use, but the efficiency is become lower. Beside, the broken of one rib will lead to the increase of pressure of others rib. Then, the umbrella will totally fail to perform its function when the others ribs started to wear off.

Active Redundancy

It is an application that redundant all the time. 

Example: Single wall hanging cloth

Figure 8.3.2

The figure above show the single wall hanging cloth. The metal ring use to hang the cloth at one time. If the metal ring is broken, the hanging cloth will completely failure to function and it cannot be use to hang the cloth. 

Passive Redundancy

Act as an application of the redundant element. It used when the active elements fail to perform it’s function.

Example: Singer's sewing machine

Figure 8.3.3

 The figure above shown the image of Singer's sewing machine. The spare needle found along with the machine when we buy it.. When the needle is broken, rust or missing, it will leads the machine to be failure functioning. So, the presence of spare needle act as a replacement , enable the sewing machine perform its function.

Ockham’s Razor
Ockham's Razor proposed that when a few similar function’s design is presented, the design with a simplest way to obtain the same function is chosen. The design that has been chosen than other design because it is simplest design.

Example: lighter and matches

 

Figure 8.4

Based on of this two(2) of light up the fire,user always prefer a lighter to light up the fire because it more than a matches.It is complicated to use a matches than the lighter because need rub stick,cover the fire,our hand feel hot and the fire not light up long lasting.

Form Follows Function

The beauty of design that had been created from it main function and purpose.

Figure 8.5 

As we can see from the figure above, there are two different type of luggage bag with the same purpose which is to carry stuff. The design of the red luggage beg is more stylish, nicer outlook compare with the old fashion purple luggage bag. Besides, it’s main purpose is remain there but the presence of wheels made a luggage become easier to be carried.

Flexibility-Usability Tradeoff

A design which can perform multiple of function may affect the performances of the design, therefore lower the design’s usability. 

Example: Casio watch

Figure 8.6

As we can see, the Casio watch have many functions as it show  time, date, day, calculate the time taken for a lap, calculate simple mathematics, set alarm and perform as a stopwatch. The presence of many functions in a watch may confuse the user where which button is contribute to which functions. The design of tiny size button will make user hard to press it, especially when they need to use the calculator. It leads to time consuming when perform the calculator function and reduce in efficiency when calculating.