CapSense Proximity detection with small target object

[ThWe_4461836]

Hi everyone,

I am new to the cypress system and capacitive sensing.

I would like to use the CapSense proximity code to detect the presence of a small object (small conductive ball) 2 mm of diameter

I am using the CapSense_CDS_P4_Proximity  example code

I have built the sensor simply by using copper tape as the sensing element and polyamide tape as the overlay as can be seen in photo below

The problem is I cannot detect the ball using the default automatic setting of the code since the charge of the ball is very small, compared to a finger.

I am not sure what parameters I need to tune in order to be able to detect capacitance from the presence of the ball over my sensor.

Moreover, if the sensor becomes too sensitive I believe I need to also shield it from external environmental objects that might cause some noise such as nearby objects. Thus, what would be the optimal shielding method in this case.

Your help is very much appreciated.

Thank you !

[VenkataD_41 · Accepted solution]

Hi,

In your application the target object is very thin and it is not grounded too. So the parasitic capacitance it would add to the proximity sensor would be very less and that change in sensor capacitance may not be able to get significant difference in raw count.

For your application, you may need to have several thin traces connected at the end. In between those sensors you need to put traces of ground as shown in the image attached. Please note that the sensor traces should be thin and the gap between the sensor traces is equal to the metal ball thickness. The total parasitic capacitance of the sensor should not exceed 2--pF for better sensitivity.

Please go through the Manual tuning section  PSoC 4 and 6 CapSense design guide.

Please note that you have tune the sensors in such a way that when the metal ball is placed on the sensor, the raw counts would go up by 5 times than the rawcounts caused by noise.

Thanks

Ganesh