1. “ The use of
additional visual,
through changes
in lighting, or audio
feedback, can be
used to compensate
for the reduction in
tactile response
”
The power of touch
by Jerry abraham, Central Product manager, RS Components
Technological progress has dramatically changed the way that we interact with
machinery, and reshaped assumptions of how user interfaces are designed.
Early human-machine interface (hmI) designs were products of necessity.
Before electronic control systems
became the norm, people
were accustomed to using mechanical force
technologies, such as membrane contacts,
have been in used for many years.
Touchscreen interfaces on mobile phones have
prototyping and acceptance testing of HMI
designs to gauge user reaction.
1241 series that include O-ring seals to protect
against liquid ingress.
and resilience without the drawbacks of
capacitive technology.
mechanical feedback. In systems where it
is important to demonstrate to the user that
contact has been made without involving
to interact with a piece of machinery. They demonstrated more recently that the absence Because legends can easily be overprinted As the travel distance on vandal-proof ITW’s ActiveTouch technology, employed in the another form of feedback, tactile response
used levers and long-travel switches to make of tactile feedback is no hindrance to usability, on custom layouts, the look and feel of pushbuttons can be limited, many of these company’s T01 series, uses built-in transducers remains important, providing applications for
and break physical contacts or move gears as long as the system responds consistently the membrane keypad can be more easily devices can be ordered with built-in LEDs to supply an ultrasonic signal that is damped devices such as the Arcolectric T09 series.
into place. The only places we see those types and immediately. integrated with the overall industrial design that change state when pressed to give the by contact with a user’s finger. This reduces But the evolution of electronics has shown
of control today are in systems that need a of the complete system. This can be used user better feedback. Making the switches the ‘ring down’ time of the ultrasonic pulse, that there is much more to HMI design
mechanical override, such as the emergency The use of additional visual, through changes to provide the consistent look and feel that is purely touch-sensitive rather than relying on similar to the damping of a bell after it is struck. than tactile feedback. Manufacturers have
exit doors on trains or aircraft. in lighting, or audio feedback, such as the use considered by ergonomists to be an important switch travel can improve the resilience of A microprocessor detects this change in decay responded to this evolution with a greatly
of synthesised or sampled ‘click’ sounds, can factor in ease of use. the HMI and make possible a wider range of and signals whether the button has been expanded range of options that support all
As electronic control began to predominate, be used to compensate for the reduction in panel designs that are not restricted by the pressed or not. forms of industrial design.
the lever – which needed a lot of force to tactile response. Many HMIs have to survive hostile conditions – techniques that need to be used to protect
operate – gave way to the pushbutton that they may be splashed by liquids that then seep moving elements against deliberate vandalism. Another approach is piezoelectric sensing,
could switch between two closely spaced One advantage of non-pushbutton designs into the equipment through gaps between employed by Apem in its PBA series of
circuit traces. The assumption remained that lies in design flexibility. Take, for example, the switches and mounting. And problems in In difficult environments, the capacitive buttons. A piezoelectric sensor uses the See the latest aPEm and ITW hmI
users like to have tactile feedback when they the AC3875 kit manufactured by Apem. This outdoor equipment such as parking meters touchscreens favoured by high-end mobile change in pressure on the surface of the ranges at rswww.com/electronics
use pushbutton-based interfaces. However, membrane keypad provides the customer the includes the actions of hostile users. Vandal- phones and consumer products are often button to change the voltage presented to a
the rise of touch panels has demonstrated that option to insert their own custom graphs for proofing pushbutton switches is difficult but impractical. Because they rely on body monitoring microprocessor.
people do not need the sensation of travel in a specialised designs. It is possible to punch manufacturers have succeeded in closing off capacitance, they frequently do not respond Get more online...
switch to be comfortable using a system. holes in the keypad to show the state of avenues of attack so that buttons cannot be to users wearing gloves. Manufacturers This does not mean there is no place for the
Share your views on hmI technology
LEDs mounted behind it as the individual prised out of their mounting. Examples of such as Apem and ITW have developed traditional pushbutton switch. People are
integration at www.designspark.com
Interfaces that use low-travel switching pads are pressed. Overall, this allows the easy vandal-proof products include the Schurter technologies that provide touch-sensitivity used to the idea of the Stop button with its
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