Toggle Capacitive Touch Sensor Breakout - AT42QT1012

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You certainly are a great help for me Bob. As you may have guessed I am a complete beginner at some of this process and am finding my way along one stumble at a time but I must say, I am having the best fun doing it:-)
The Powerboard has an enable pin which when connected to ground disables the Powerboard. The switch carries no (or negligible) current as it simple connects the Enable pin to Ground via a signal. So when toggled “On” the EN pin is not grounded and when toggled “off” the pin is grounded and the board disables. Adafruit Data sheets says it this way

“* EN - this is the ‘enable’ pin. By default it is pulled ‘high’ to VS . To turn off the booster, connect this pin to ground. The switch can be as small as you like, it is just a signal. Contrast this to an inline power switch which would have to be able to handle up to 2A of current! When the chip is disabled the output is completely disconnected from the input.”

From this I have deduced that the switch is carrying a minimal load and should be able to handle it easily but the fact is it just keeps turning itself on and off. Rght now as I sit here at my desk every 4-5minutes it turns the Powerboard output on for about 3 seconds then off again. Very strange behaviour and I am wondering if it is a faulty board? Or alternatively the power output from the Bat pin to the touchswitch is not consistent and the switch just becomes unpowered then when the power comes on again the switch is powered and comes on. I will test this with an outside power source for the switch.

I measured the voltage drop across the 3R3 Resistor as 1.8v so calculated the current as 545 mA which is in line with my calculations for the current draw of the LED. I hope I got my calcs right?? And my thinking was also that the powerboard couldn’t handle the load but it is a spec’d as being able to handle 1000mA and certainly when switch via a normal toggle it will run forever if USB power is supplied and for a couple of hours if running off the Lipo 2000mAH battery.
Again thank you for your help and advice.
les

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22

That all adds up. You had not specified the LED type but understand now.
Just a quick read on that switch. It seems to have a built in OFF timer. I am not familiar with this device but maybe if you read pages 17 and 18 you may get more clues. What have you done with the timer pin? I am getting the impression that the switch is doing it’s normal thing and timing out and something special has to happen to keep it on. I am sorry but I just don’t know and I don’t have one to investigate further.

Another way would be to interface a “latch” of some kind between this switch and power unit but this probably could get a bit messy. I am assuming you want a touch ON and touch OFF function. The auto off timer is apparently used in case the switch is left ON accidentally.
Cheers Bob

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Good suggestions Bob, I have read the information on Page 17 and can see what you are referring to. My problem is that Adafruit in the description of the switch say "We designed this breakout to have infinite time-out. " and I have taken that as the case but now in reading the additional information you have pointed out I am becoming very sceptical of the accuracy of the Adafruit statement.
I have contacted Adafruit via their Forum and will see what comes back. That will be tomorrow at earliest if I get an answer.

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