Sensor Ganging--Optimize Power in a Capacitive Sensing System — Part II: Page 3 of 3

August 13, 2015 //By Shruti Hanumanthaiah and Subbarao Lanka
Sensor Ganging--Optimize Power in a Capacitive Sensing System — Part II
Shruti Hanumanthaiah and Subbarao Lanka continues to consider the challenges of sensor ganging and how to optimize power in a capacitive sensing system.
ON, thus enabling the user to locate the interface even in the dark. Even before the hand touches the sensors, the backlight LEDs turn ON to enhance the visibility of the interface for use even in the dark. Thus the system response to an approaching hand is faster because of proximity detection. After switching the LEDs on, the individual sensors are scanned independently.

Pin count reduction

Instead of a dedicated proximity sensor, a ganged sensor can be tuned as proximity sensor. In an application that uses a small pin packaged device, this approach saves one or more number of pins, depending on the number of proximity sensors in the application.

Increased proximity distance

a)    Combining all proximity sensors used for gesture recognition increases the proximity-detection range for detection of an approaching human hand.

b)    Combining touch sensors with an existing proximity sensor increases proximity range for a given board size where the proximity sensor size is restricted.

In Part II, we have covered trade-offs between response time and power consumption, as well as other issues resolved by a ganged sensor.  In Part III, we will cover sensor ganging implementation and more techniques to optimize power consumption in a ganged sensor application.

Resources:

To understand more on how to calculate average power consumption for a capacitive sensing controller, refer to AN66308 - CY8CMBR2044 CapSense® Design Guide

Reference:

Sensor Ganging—Optimize power in a capacitive sensing system--Part I
   

Design category: 

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