If you have ever felt the “click” of a button on your computer mouse or the “bump” of the home key on a smartphone, you know the feeling of tactile feedback, also known as haptic feedback. But why do some user interfaces not “click” when you press them?
User interfaces without mechanical buttons, sliders or knobs do not respond with natural tactile feedback. For example, touch screens, touch pads and capacitive touch buttons do not inherently provide tactile feedback when touched. There is no click or bump to say, “Hello, I received your input.” Designers may choose these types of interfaces because the location or environment requires sealed enclosures, improved durability or more reliable operation. Or, perhaps the user interface is meant to display complex or dynamic content that is best conveyed by a screen. There may also be an aesthetic design preference for flat user interfaces, like those used for a sleek stainless steel refrigerator or a glass stove top.
Harsh industrial environments, high-traffic commercial areas and sterile medical rooms all require user interfaces that are specialized, not only based on user requirements, but also on environmental demands. Take the gas pump keypad that needs to be weatherproof or the self-checkout terminal that needs to be durable. Designers have to balance these demands, while also providing an experience where the user can easily make selections and feel confident their input has been received.
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Why haptic feedback?
You probably remember using a gas pump keypad at some point and mistyping your credit card PIN or zip code and having to start over. Most likely, you mistyped because you did not get feedback. You pressed a button once, but you weren’t sure so you press it again. Come to find out, the machine did in fact register both presses, and you ended up with more sevens than you expected. This is where the absence of haptics leads to a few key problems.
- User interface latency. The machine appears slow to the user, because it does not give immediate feedback. This is often a case when a machine has limited resources and has to process other information in the background.
- More input errors. This may seem like a surprise, but when there is no haptic feedback, users have to focus more on the activity at hand. Try typing on a smartphone with haptics and without haptics, and notice how your accuracy and speed improves with the haptics-enabled one.
- Increased mental loading. In automotive infotainment systems, your mental effort needs to be focused on driving. If you cannot latently feel and must look at the infotainment system, you will spend more time adjusting the station and less time driving. The automotive industry measures mental loading and mental effort with two metrics called "glance time" and "number of glances," which have both been seen to decrease with haptics-enabled systems. Other industries face similar issues when operating heavy machinery or equipment.
Implementing Haptics
Hopefully now, it makes a little more sense why haptic feedback is important for a variety of applications, especially for white goods or factory equipment. The good news is that implementing haptic feedback can be easy and straightforward. It requires four primary components:
- Touch input interface: The touch input interface is the screen, keypad or individual button that the user touches to provide input to the system.
- Touch controller or microcontroller: The touch input IC determines what is detected and how to respond.
- Haptic driver - The haptic driver ties the touch input and the actuator together. It can generate a click to register a button press, or along with a processor or microcontroller, it can generate more complex effects that communicate more information.
- Actuator or motor - The actuator provides force feedback and is mounted to the touch input interface or panel.
The following image is a simple example of a haptic button system. The touch panel waits for user input and once a touch is detected, the driver is notified to play an effect. The driver then vibrates the actuator that is attached to the back of the touch panel to create haptic feedback.
The following two systems are examples of how to make use of haptics to provide more advanced feedback. A haptic driver, like the DRV2605L, can be used to generate these effects, which could be added to the interface through elements like buttons, sliders or wheels.
Next time you are designing a user interface, think about adding haptics. Learn more about haptics by visiting ti.com/haptics or continue the conversation on our haptics forum to ask questions and share your knowledge.
Additional resources:
- If you want to get started prototyping right away, consider checking out the DRV2605EVM-BT Haptic Bluetooth Kit. The kit, along with many more exciting haptics demos, will be on display at CES 2015. Come visit the TI Village in the North Hall, N115-1118, or keep up with news from the show at ti.com/CES15.
- Learn more about haptic solutions for industrial applications.
- Keep reading about the design value of haptics in this guest blog from Immersion.
