How to easily add haptics to your display: Page 2 of 3

June 28, 2018 // By Chris Chinnock
Adding haptic technology with a tactile touch sensation to touchscreen displays has become a significant design trend within many industries. Automotive, industrial and medical interfaces where the users can't always visually confirm touchscreen actions are clear areas of need for haptic technology. While a number of solutions exist, all involve trade-offs in terms of size, power and functionality.

Chaput also provided a comparison chart showing an energy use comparison with the existing piezo drivers and two other popular haptic solutions: Eccentric Rotary Mass (ERM) devices and Linear Resonant Actuators (LRA) which are already used in devices like your smartphone. And, the new driver is tiny, just 4x4mm in a standard QFN package.

Data extracted from Haptic Energy Consumption,
Application Report SLOA194, Texas Instruments,
May 2014. Data point for Boréas was extrapolated
from measurements with Boréas' driver.

What is great about the PowerHap series is the ability of the actuator to cover the full range of human touch sensitivity.

The Boréas driver in its tiny 4x4mm QFN package.

That's because the piezo actuators can be driven with a variety of signals with different shapes and frequencies. The shape and frequency of the signal can impart a different "feel" while the amplitude can set the intensity or impact that the signal has on the person. High amplitude signals can deliver strong displacement and G forces providing very positive feedback signals - like a button click.

According to Professor Hong Z. Tan, a haptics expert at Purdue University, "The human touch threshold is dependent upon the frequency of the signal and we are more sensitive to signals above a frequency threshold that is around 100Hz. What that means is that at 300 Hz, a displacement of only 0.1 micron can be detected but if the stimulus is at 3Hz, one needs a displacement of 10 microns to feel it. Generally, you want to deliver signals that are about 10-20 dB above the threshold to be readily detectable."

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