Proximity Gesture Applications In Automotive HMI: Page 3 of 6

January 20, 2016 //By Sivaguru Noopuran, Cypress Semiconductor
Proximity Gesture Applications In Automotive HMI
In this article Cypress Semiconductor look at the use of capacitive proximity sensors in automotive applications. These sensors can be used for simple actions such as keyless entry or turning on cabin lights and sensing an individual in the vehicle. However in this article Cypress focus on how you can now use them as inputs into systems such as media players and navigation systems with vehicles by using the same principles.
it will be one of the below, depending upon the position of the hand and sensitivities of the individual sensors:

Left → top → bottom → right
Left → bottom → top → right
Left → bottom → right
Left → top → right

All of above sensor activation sequences are mapped to the (left → right) gesture. A PSoC is used in this case for implementing the capacitive proximity sensors. A Capacitance to Digital converter (known as Capsense Sigma Delta) inside the PSoC is used to measure the capacitance. The output of the CSD module is referred to as rawcounts. The higher the rawcounts, the greater the capacitance sensed by the sensor. The presence of a hand close to the proximity sensors increases their capacitance.

When rawcounts of the sensor crosses a certain threshold from its base value, we say the sensor is triggered due to presence of an object in its proximity. The rawcounts plot of the four sensors as a hand draws a straight line from left to right as shown in Figure 2 (a) is shown in Figure 2 (b). The plot confirms the order of activation of sensors mentioned above. If hand moves in opposite direction, that is for a (right → left) gesture, the sequence in which sensors are triggered is reversed with respect to the left and right sensors in the above mentioned sensor activation sequences. That is, the sensor triggering sequence will be one of those below for a (right → left) gesture:

Right → top → bottom → left
Right → bottom → top → left
Right → bottom → left
Right → top → left

The above two gestures mentioned involve movement of the hand in the horizontal direction. Similarly, if the hand draws a straight line in the vertical direction, then it can be either a (top→bottom) gesture or a (bottom→top) gesture, depending on direction of hand movement.


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