I have a question about the SparkFun Capacitive Touch Breakout - AT42QT1010…
Specifically:
I was attempting to use battery power for this device and hooked up 3 AA batteries in series to yield 4.5V. Put the +pole into the VDD pin & the – pole into the GND. It seemed to work partially—when the sensor was touched, the LED came on and there was a voltage signal from the out pin—however, the voltage was much smaller than expected, less than 100uV. Also, the baseline seemed noisy.
When the same component was powered via an Arduino board after connecting the Arduino power via a USB to a computer, it also functioned, but the output signal voltage was +5V.
Finally, I am wondering if one could power the AT42QT1010 using the power output from a USB cable connected to a wall charger… or if there might be a current overload.
Thanks so much for any info.
You could try 4 batteries instead? It sounds underpowered
Yes, USB from a wall charger should be fine…or even a portable battery pack
Thank you. Let me try. I was worried that with the 4 batteries is would be 6V and be too much for the circuit…
Eh, the voltage regulator is rated for 5.5, the chip it good until 6v…I’d try USB first and see if it is normal. Then you can test the batteries; there’s likely enough headroom/voltage drop for it to be fine…if it burns it up I’ll send ya a new one 
Thank you TS-Russel.
Using the batteries the LED comes on but the output signal is very small. USB to computer works perfectly. USB plugged into a wall charger sends it into an oscillatory mode giving repetitive 5V signals! …. So interesting that the batteries don’t really work; I’m guessing not enough current. But all good, I can use the computer output to the USB…
Susan