aptics, or tactile feedback, is the response felt when clicking a switch, turning a knob or pressing a button. The advent of touch controls—capacitive, resistive, or even pressure sensing—has led to dynamic, engaging interfaces, but lost the realism that people expect from the physical world. The sense of touch is important to the overall usability and intuitiveness of an interface. Interfaces that use tactile feedback increase the user’s confidence that the interface is responding as expected. By incorporating tactile feedback into a well designed interface, a designer can reduce confusion and frustration.

Tactile feedback is added to a user interface through the effective use of force and vibration. Force feedback is commonly understood by its use in gaming joysticks, or the typical steering wheel in a car. Tactile feedback created by vibrations can be used to create effects that mimic mechanical responses such as the “click” of a button, the bounce of a rubber snap dome, or a sliding list of names.

With the proliferation of touch interfaces in many of today’s popular consumer devices, haptic technology is being broadly adopted by designers and OEMs as a way to bring a physical sense of realism and engagement to dynamic interfaces. Today, haptic technology can be found in popular smartphones and tablets. More recently, auto manufacturers have been implementing haptics as a way to increase user confidence and improve the usability of auto interfaces.

Today’s mass-produced implementations of haptic technology for touch interfaces use a motor, or actuator, to create vibration effects that are designed to replicate a tactile sensation, such as a button click, or a rapid tick that associates with a scrolling dial. A click, for example, can be a very specific single pulse at 120 Hz that gives the impression of a metal snap dome, where as a rubber dome switch might be emulated with a 90 Hz pulse.

While exactly emulating reality can be achieved, the primary purpose of haptics is not to deceive a user into thinking they’ve pushed an actual button, but to provide physical confirmation of their action. One of the more valuable aspects of haptics is the ability to control the “mechanical” response of the touch interface with sophisticated programming to communicate with the user in direct ways.

Here are a few use cases to illustrate user communication through haptics in a simple photocopier touchscreen interface:

• Confirmation on the number pad when entering the number of copies—simple confirmation, no annoying “beep”
• Switching between fax/copy/scan modes—different effects notify the user
• Hitting the “Copy” button with no number of copies selected—error effect tells the user that the button is working, but they haven’t provided needed information
• “Greyed out” areas or buttons have no haptic response—tells the user these aren’t active buttons

As the market for haptic technologies has grown, there have been many companies in the haptic ecosystem engaged in creating compelling, high-quality solutions to bring haptic interfaces to a wide range of markets. Due to cost, complexity, and IP constraints, these solutions have taken a long time to become viable for commercial equipment. Over the past few years, developments have progressed that now make haptics accessible and viable for appliance interfaces:

• Several semiconductor manufacturers have launched parts containing embedded haptic libraries.
• Availability of motors/actuators for non-mobile phone use (via suppliers such as PMD) has increased.
• The mechanical solution to support non-mobile applications has been simplified to make it easy and inexpensive to design haptics into products.

Semiconductor solutions

Looking for an off-the-shelf solution to integrate haptics in commercial equipment today, appliance designers have the following options:

• Cypress Semiconductor. Cypress delivers high-performance, mixed-signal, programmable solutions that provide customers with rapid time-to-market and value.
• Atmel Corp. Atmel designs and manufactures microcontrollers, capacitive touch solutions, advanced logic, mixed-signal, nonvolatile memory and radio frequency (RF) components. Atmel has incorporated haptics into their touchscreen controllers.
• Microchip Technology Inc. Microchip, a provider of microcontroller, analog, mixed-signal and flash-IP solutions, offers its mTouch™ Sensing Solutions portfolio, with four turnkey controllers for multitouch projected-capacitive touchscreens and touchpads, proximity detection, and haptic touch feedback.
• Texas Instruments. TI delivers a broad portfolio of amplifiers and linear solutions including op amps, audio amplifiers, linear amplifiers, instrumentation amplifiers, programmable gain amplifiers, current shunt monitors, comparators and variable gain amplifiers.

There are several other vendors who are working on similar parts that will be coming to market shortly. As it stands, integrating haptics has gone from a requiring a custom software license only obtainable from one company to a commonly available feature from multiple vendors, in a few short years.

Actuators

Actuators are the source of the mechanical vibration that generates haptics. The most effective and common form is the Eccentric Rotating Motor (ERM). These motors are typically long lasting (for commercial use), inexpensive, and provide the right amount of mechanical force to emulate buttons and UI elements.

The primary market for most actuators is mobile phones. Compared to the volumes consumed in that industry, everything else is small. A few vendors, aggregators such as Precision MicroDrives, or motor suppliers such as Johnson-Electric, recognize the need to support smaller volumes (up to 100,000) that are needed in commercial, R&D or other applications.

This is a vital element ensuring that appliance, vending machines, remote controls and industrial controls OEMs can obtain needed parts. Additionally, Johnson-Electric’s actuators are automotive rated—as such, they perform in the many varying environments found in commercial applications.

Mechanical design

The mechanical design of touch feedback solutions has been a point of complexity for many years, and has limited the ability for some to implement haptic technology. This is no longer the case; companies such as 3M have designed grommet materials that make the implementation of haptics straightforward and inexpensive.

Fundamentally, using a grommet on the mounting points of a touchscreen or touch surface, allows for a solid attachment with the minor amount of compliance necessary to enable haptic feedback. Densitron, a supplier of display modules, provides a pre-integrated solution for this purpose, or depending upon needed volumes, designers may obtain a sample reference design from any of the semiconductor providers above.

In short, to add haptics to commercial designs today, there are three steps:

1. Determine a semiconductor supplier that meets your size, price and functionality needs.
2. Select an actuator vendor.
3. Design your touch surface or touch screen to incorporate a grommet suspension.

If you choose to purchase a pre-assembled module from a supplier such as Densitron, these parts are already built in.

 Options are available for design guidance, or vendor recommendations should you have custom needs beyond those offered above.