I recently purchased the AT42QT1011 Capacitive Touch Breakout, specifically because it does not have the built-in timeout. However, when first connecting to my Arduino board, it was very inconsistent in terms of how long it would remain HIGH even though I was touching and holding my finger on it.
Then I noticed in the Guide, a note indicating that the IC “may not stay on indefinitely when powering your microcontroller with less reliable wall warts”. Seeing various related comments, I found that if I hook up the USB from my computer, the chip seems to behave flawlessly, but it does not when running from a 9V input to the board.
What is a solution to this problem, since in the field, we were intending to power the Arduino from a 9V power source, not a USB from a computer? Or another way of asking the question, what is so different about the USB input that affects the behavior of the Breakout board?
I believe that most computer USB ports have very clean power output which is ideal for the product as there is less overall noise being generated.
Most cheap ~$10 power supplies are designed to literally output the voltage and current on the label with some degree of variance. They use cheap components and as a result have plenty of noise and manufacturing tolerance.
I would think that a high quality power supply such as an authentic Meanwell supply would work swimmingly. We have several different kinds, however, I do not see a 9v version in our catalog.
If that is too much to spend then you might be able to get away with any of the big brand power supplies for smart phones as they tend to be cheaper and of higher quality. Samsung, Google, Apple, etc, come to mind, though, I cannot recommend a supplier or a specific model I am afraid, assuming you can use 5v.
I wouldn’t be surprised if an automotive USB - accy adapter (cigar lighter plug) regulated down to 9 volts input. The trick would be to find a decent one, there are a lot of lousy car accessories out there.
I am now testing to see how much amperage our system draws, since my understanding is that if I use the USB port for power, I am restricted to 500 mA. So it may well be that a better regulated power supply to the cylindrical power jack is my best bet. I will pursue that.
For the record, I have not yet tried a battery pack, but I will do that just for comparison. I have tried using an OUTPUT pin to power the board, and that exhibited the same problem.
If anyone cares to share more information, I’m curious as to why this particular board is so sensitive? or why this type of problem is not more prevalent. It seems (in my very limited experience) that everyone generally uses something like the typical 9V adapter (e.g. from Elegoo, that claims to be regulated), and I don’t hear much about this problem (just vague references here or there that some components behave well through USB, but misbehave through the power jack). But I am relatively new to the Arduino world, and there’s much I’m unware of.
I’m not badmouthing the SparkFun board, but I had tried the Adafruit board with the AT42QT1010 chip, and it behaves well with the standard power supply. I just can’t use it because it has the 40 second timeout. The SparkFun board was the only one I could find with the 1011 chip (no timeout), and I’d love for it to work.
TS-John:
I would think that a high quality power supply such as an authentic Meanwell supply would work swimmingly. We have several different kinds, however, I do not see a 9v version in our catalog.
I’ve been toiling over this and reading various articles. What about a well regulated 5V source directly to the 5V pin (bypassing the regulator). One of the Meanwell regulators you sell is the 5V LED Switching Power Supply. Although I don’t quite understand the LED aspect, would this be a viable and reliable option for power?
I am going to try powering the AT42QT1011 from an independent power supply (3V wall wart) rather than getting power from the Arduino.
a. Do I have to worry about sharing the GND?
b. If so, what would that look like? I know that I have to complete the circuit back to the wall wart. Would I also connect GND on the AT42QT1011 to GND on the Arduino?