CY8CKIT-003 PSoC 3 FirstTouch Starter Kit Guide, Spec. # 001-49613 Rev. *B
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Example Projects
4.5.1
How the Proximity Sensor Project Works
Proximity detection is performed by a proximity antenna acting as a capacitive sensor. The proximity
antenna consists of a wire connected to the proximity connector on the board.
Upon power up, the board establishes a baseline capacitance value of the board along with the
antenna attached to it. This is used as a reference value of capacitance and is called the parasitic
capacitance of the board.
When a conductive object such as a human finger is brought close to the antenna, the overall
capacitance of the board changes. This change in capacitance determines the proximity of the finger
to the antenna. An increase in capacitance corresponds to the finger being closer to the antenna.
This is used to light up the LEDs based on the proximity of the finger to the antenna. The number of
LEDs turned on increases as the proximity of the finger increases.
To establish the parasitic capacitance, the antenna must be connected to the board before power up.
The baseline for capacitive sensors is updated continuously by the firmware. This accounts for any
changes in environmental conditions during the operation.
Figure 4-18. Proximity Sensor Project Flowchart
Boot
Start
Scan the Proximity sensor
Is sensor active?
Read signal value
Yes
No
update LED display
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