Problem to control a CY8CMBR3108

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Problem to control a CY8CMBR3108

Anonymous
Not applicable
‎Aug 27, 2018 05:51 AM
‎Aug 27, 2018 05:51 AM
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Hello everybody,

I want to control the CY8CMBR3108 electrically. This sensor is located in a component,

so I have to replicate the capacitance of a finger to active the sensor.

For this purpose, we attach an electrically conductive material on the component. At
this there is a line which leads into a relay. By switching this relay, a
grounded capacitor is switched on. But this circuit doesn’t work all the time.

For this reason, I would like to ask you for advice.

Can you tell me a circuit which you can operate/control the sensor or which
capacities you need for it?

Thank you!

Best regards,

Simon

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Re: Problem to control a CY8CMBR3108

BragadeeshV
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First question asked 1000 replies posted 750 replies posted
In response to Anonymous
‎Aug 30, 2018 02:03 AM
‎Aug 30, 2018 02:03 AM
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Hello Simon,

Please tell me if I have understood your issue correctly. Do correct me if I'm wrong. You need to simulate the finger capacitance and test your MBR3 device. But with the present circuit, it is not working as expected.

I may need further clarification from your side.

1. Dimensions of the Cu plate

2. Capacitance of the grounded capacitance that you are using as a finger capacitance.

3. How do yo validate that your circuit is not working? Is your device not detecting the touch?

4. How are you checking if there is a not touch or not?

For now, I believe that this issue could be due to one/more of the following reasons:

1. MBR3 uses SmartSense algorithm, and it can handle only a Cp value of less than 45pF. This capacitance is added due to a lot of factors such as trace length, trace width and dimensions of the sensor.

2. If not already, you need to put a series resistor of 560 as shown in the below document. This will act as a low pass filter.

Refer : http://www.cypress.com/file/41076/download Pg 43.

3. Since there is a relay line in between, the switching transitions may emit radiations and will affect the sensor.

Regards,

Bragadeesh

Regards,
Bragadeesh

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