Breakout board for AT42QT1010

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PantAaroN
 
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Breakout board for AT42QT1010

Post by PantAaroN »

Hello,

I purchased the capacitive touch momentary capture button and I am having a difficult time finding the schematic for the breakout board. I understand it is a simple circuit, but finding the values for the capacitor/resistor components is very difficult on such a small device. The sensitivity of touch is determined by the value of these components, and right now this sensor toggles when my hand or anything touching my hand comes within a 1cm proximity. I need this button to toggle on press only, and not when I pass my hand by it. If anyone has any general knowledge of the subject, please feel free to add any information you can.

Product purchased:
http://www.adafruit.com/products/1374#Description

Thanks a lot, I look forward to your replies.

Aaron

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adafruit_support_mike
 
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Re: Breakout board for AT42QT1010

Post by adafruit_support_mike »

I don't know if the schematic has been cleaned up for publication yet, but the circuit follows the recommendations in the datasheet: http://www.adafruit.com/datasheets/AT42QT1010.pdf.

The resistor closest to the sensor is a 10k, the capacitor directly above the sensor is the ever-present 100nF debouncing cap, the resistor off to the right hand side of the board is a 1k current limiter for the LED, and the capacitor off to the left is the sampling cap. I don't know the exact value on that, but would expect it to be in the suggested range of 2-50nF. At a guess, I'd say it's toward the high end of that range for the sake of stability.

I'll ask one of the designers for an exact value.

adafruit
 
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Re: Breakout board for AT42QT1010

Post by adafruit »

Check out the schematics at http://learn.adafruit.com/adafruit-capa ... /downloads for all values :)

PantAaroN
 
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Joined: Tue Jul 23, 2013 1:47 pm

Re: Breakout board for AT42QT1010

Post by PantAaroN »

Just letting everyone know, the problem has been fixed. In case you are trying to get this particular breakout board to toggle on touch and not proximity, the value for Cx is not high enough. Cx is the acting touchpad on the board itself that acts as a capacitor to ground. I wired my own button (just a big hunk of metal) to the hole made for replacing the button, cut the trace going from the touchpad on the board to the new added button, then put a 33 pF capacitor from this new metal button to ground. You may need to play with the capacitor values a little bit to get it to do what you want but this is what worked for me.

Hope I helped someone out,

Aaron

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rcwelsh
 
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Re: Breakout board for AT42QT1010

Post by rcwelsh »

Hi Aaron,

Excellent -- this is exactly my problem. I spent all of last night attempting different means by which to design sense electrodes and they all seem to be working in proximity mode. I am building a touch pad that needs a sensor about 2.5 x 2.5cm.

Thanks for the post and I hope this works for me tonight!

-Robert

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