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CAPSENSE™ & MagSense

ltdndt
Level 1
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Hello, 

I would like to make buttons that can detect a conductive object put on the overlay. 

I was thinking about using the CY8CMBR3110 and self capacitance measurement but I don't  know what configuration would be best as the object won't be connected to ground.

  • Configuration 1 : Sensors with a fishbone pattern (Rx = capsense signal and Tx = ground) with hatched ground plane connected to Tx (but won't my parasitic capacitance be too high ?)
  • Configuration 2 : Sensors with a fishbone pattern (Rx = capsense signal and Tx = ground) with hatched ground plane but clearance between Tx and ground plane
  • Configuration 3 : Round sensors with hatched ground (normal button configuration if you want to detect touch event)
  • Or something different ?

 

Also is it possible to use several buttons at the same time ?

Lastly, if we disabled the auto reset, how long the sensor can stay in the ON position ? Can we let an object on the sensor for several hours and the presence will still be recognized ?

 

Thanks in advance, 

Have a nice day

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Hari
Moderator
Moderator 750 replies posted 500 replies posted 250 solutions authored
Moderator

Hi @ltdndt 

 

What is the size of the object that needs to be detected? If it is a large object that can extend to the hatched ground region, then Configuration 3, Round sensor can be used as this would induce larger coupling to ground to the conductive object. 

Also, how many sensors are planned to be used for object detection? 

 

If the sensor auto-reset is turned off, then the sensor will report the ON status till it is reset (either by XRES or power cycle). 

 

Best regards, 
Hari

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Hari
Moderator
Moderator 750 replies posted 500 replies posted 250 solutions authored
Moderator

Hi @ltdndt 

 

What is the size of the object that needs to be detected? If it is a large object that can extend to the hatched ground region, then Configuration 3, Round sensor can be used as this would induce larger coupling to ground to the conductive object. 

Also, how many sensors are planned to be used for object detection? 

 

If the sensor auto-reset is turned off, then the sensor will report the ON status till it is reset (either by XRES or power cycle). 

 

Best regards, 
Hari

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ltdndt
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hello @Hari

 

Thanks for your response !

The object is a cylinder (diameter = 16mm and height around 3mm). I was thinking about making round button with a diameter of 10mm. Should be enough ? My overlay will be 4 to 5mm.

I want to use 8 buttons at the same time.

 

Best regards,

 

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Hari
Moderator
Moderator 750 replies posted 500 replies posted 250 solutions authored
Moderator

Hi @ltdndt 

 

Detection of this through a 4 mm overlay would be difficult. Is the cylinder going to be placed vertically (i.e. the 3mm base resting on the sensor) or horizontally, with the longer side on the sensor? With the 3 mm base on the sensor, it would not be possible to detect this. 

 

Can you move to the PSoC MCU line of devices so that we have manual tuning controls?

 

Best regards, 
Hari

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ltdndt
Level 1
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Level 1

Hello @Hari ,

The longer side will be placed against the overlay. 

Like that : 

figure 1.pngfigure 2.JPG

Don't we have manual tuning with the CY8CMBR3110 as well ? I  wanted to set the threshold myself and disable the auto tuning. I wanted to use EZ-Click.

 

What family of PSoC do you recommend ? Is the software development easy to do ? We have to use PCoS Creator, is that right ?

 

Best regards,

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Hari
Moderator
Moderator 750 replies posted 500 replies posted 250 solutions authored
Moderator

Hi @ltdndt 

 

The longer side being present on the sensor is definitely advantageous. 

 

Don't we have manual tuning with the CY8CMBR3110 as well ? I  wanted to set the threshold myself and disable the auto tuning. I wanted to use EZ-Click.


No, we can only set the thresholds in MBR3. We cannot tune the sensors manually or adjust the gain in this device. 

 

I would recommend PSoC 4 - specifically the 4000S device as it contains a newer CapSense IP with better coverage of such corner cases. The software development is easy and we have a lot of code examples to get you started with the design. 
Yes, PSoC creator is the right platform for application development.

 

Best regards, 
Hari

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