CAP1188 different behavior when on USB Power vs Wall Power

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ksbdude
 
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CAP1188 different behavior when on USB Power vs Wall Power

Post by ksbdude »

Hello,

I have a CAP1188 breakout board hooked up to an Arduino mega and everything works perfectly when I run the Arduino powered over USB from a computer. However if I power the Arduino through the barrel jack then the cap1188 becomes unreliable. When powered through wall power a capacitive sensor when held down will not stay triggered reliably and sometimes wont trigger at all even though it works perfectly when powered over USB port from computer. I have tried a variety of wall warts from 9-12v all the way up to 5 amps with no success. The problem also persist if I use the USB port and cable into a USB wall power supply.

Could not having a serial connection to a computer affect anything?

Any advice is really appreciated! Thanks in advance.
-Kevin

https://www.adafruit.com/product/1602

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adafruit_support_bill
 
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Re: CAP1188 different behavior when on USB Power vs Wall Pow

Post by adafruit_support_bill »

Capacitive sensing can be affected by grounding and or noise. USB ports typically have a pretty well-filtered 5v supply. Many wall-wart type supplies have a fair amount of residual switching noise that can cause problems in sensitive circuits.

Have you tried powering via a battery pack? That would help determine if the problem is grounding or noise.

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