Capacitive Touch sensors (ttp-223 and AT42QT-1011) issues

Other Hardware Sensors
1

Hi, the main thread on my project is here, but I'm having some issues with my capacitive touch sensors so I thought I would ask in here.

My issue resolves around the capacitive touch sensors. The ttp-223 sensors i am using (connecting a Mega), with a copper ring soldered directly to the sensing pad, will sense through 1 cm of wood with no issues and trigger the corresponding leds. Unfortunately they (appear) to have an 'auto-calibration' function that runs every 7-8 seconds so after that time it stops being 'triggered'. From all of the searches I've done this seems to be a 'feature' of this model. If any-one knows a way to stop this or circumvent it in code I would be most grateful.

ttp-223 datasheet: ttp-223 datasheet

ttp-223 I have: version I have

I've bought a few AT42QT-1011 link from sparkfun to see if these would work as the datasheet suggests they stay 'triggered' for as long as something is sensed. I'm having mixed results. Some times it will stay triggered for as long as I touch the sensor with my finger and some times not. Also, I've tried adding an external pad of just copper tape so I can sense through the wood and this has the same mixed results (through the wood). Some times it stays triggered, some times it doesn't.

Any help on how to alter the TTP-223's to stay triggered or how to deal with it in code would be amazing also how do I build an external sensing pad for the AT42Qt-1011's that will both sense through wood and stay triggered?

Thank you all for you time.

Adam

2

Hi,

Just giving this a bump to see if any one has any ideas.

Adam

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I'm having the same problem with a different model (ky-036), wondering if you've found a solution?

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Hi Brad,

I went with the AT42QT-1011s with an external pad of about 4cm diameter copper tape. Though they weren't t as sensitive at the TTP-223's with a copper ring soldered to the pad. They did stay 'triggered' when in the table. What was odd is they were flaky when I was testing and connected to the bread board.

The difference in sensitivity was that with the 1011's i have to touch the table or be 1-2mm from it where as the ttp's I could be a good centimeter or two from the table and it would trigger. If I do some thing like this again I will look at getting a custom board made as I think the actual chip on the ttp-223 can be set to not auto-calibrate..

All the best,

Adam

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Thanks! If it helps you, after I posted that question, I did find this video that shows how to make your own touch sensor. I just ordered some resistors so I haven't tried it yet.

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Hi Brad,

Thanks for this!

Kind Regards,

Adam

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If you need to add user input without using a button, then a capacitive touch interface might be the answer. The AT42QT1010 SparkFun Capacitive Touch Breakout offers a single, momentary capacitive touch button with easy-to-use digital I/O pins.
regards: propane gas smoker

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