Touch sensor problem AT42QT1070 always on w/extension wire

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Peterson!
 
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Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

I am having a problem. This component does not perform properly. When I extend the touch pad via a wire in standalone mode it is constantly on. It does not react to touch. With out a wire I can carefully touch the solder connection on the board and it works. I ordered new ones to try again but am concerned about using them, and furthermore not sure what the problem is. I would appreciate any advice. Thank you!

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adafruit_support_bill
 
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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

When you extend the touch pad, it becomes considerably more sensitive and can even sense at a distance. I have also found that it is best to keep hands (feet and other body parts) away from the circuit while it is powering up & self-calibrating.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

Well then this product does not perform as described. I am dissapointed can I return the products? I am against a deadline and ordered more thinking it was a problem or faulty with expedited shipping. It now seems this product is unreliable.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

Well then this product does not perform as described.
This behavior is as described in the tutorial:
Sensor Pads

Attach the connecting wire to any conductive object or surface. That surface will become touch sensitive. Larger surfaces tend to be more sensitive. You will be able to sense through fabric, plastic glass and many other non-conductive materials.

Note that the wire will be touch sensitive too! Be sure to route any connecting wires away from areas where they might create an accidental touch input.
If you can give us some more detail about your application and how you have extended the sensor, we may be able to assist you. If you just want to return it, please contact [email protected] with a link to this thread.

Peterson!
 
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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

Hello and thank you.

I have extended the contacts with and insulated wire very similar to what I saw in the images on the website. I need to extend a distance of approximately 15 inches. I would love to use this product but the solution must be reliable.

I appreciate the help and if it cannot be resolved I will return the product although I would rather use the item of course.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

I need to extend a distance of approximately 15 inches.
Do you need sensitivity along that whole distance, or just at the end?

I set one up on my bench with a piece of 24awg insulated wire about 18" long. With the wire laying out straight on the bench, it will detect my hand from about 2-3" away anywhere along the wire. If I put a grounded shield over parts of the wire, those parts are no longer sensitive.

Depending on what kind of sensitivity pattern you want to achieve, you may also find the "guard channel" (channel 0) to be useful. Pages 11/12 of the spec sheet explain the guard channel. http://www.adafruit.com/datasheets/AT42QT1070.pdf

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

I am sorry but I do not understand the circuit 0 or the ground shield. Can you refer me to some additional info please.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

The guard channel can help prevent false positive readings. Pages 11/12 of the data sheet linked above describe how it works.
A grounded shield is simply a conductive sheath around the wire and connected to ground.

I asked if you need sensitivity along the entire length of your 15" wire, or just at the end. If you can be more specific about what you are trying to achieve with this device, I can offer more specific advice.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

Pardon my ignorance and misunderstanding. I need only contact at the end of the wire please

I better understand the solutions you speak of now and will experiment. Thank you for all the help, I am grateful.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

I tried a grounded wire this evening to no avail. I will await more guidance.

thank you

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

A photo or diagram of your setup might be helpful. If you only need touch sensitivity at the end of the wire, there are a couple of ways to approach it.

If your touch sensitive area is on a panel of some sort, you can route the wire perpendicular to the back of the panel as shown in the tutorial: http://learn.adafruit.com/adafruit-capa ... trol-panel

The other approach is to run a second 'guard' wire or foil tape over the sensor wire where you don't want it to be sensitive and connect the guard wire to channel 0. IF the guard wire is triggered on channel 0, it will prevent triggering on any other channel.

I have also had luck using a grounded sheath as a guard, although it is somewhat less sensitive that way.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by Peterson! »

I have had no luck with the solutions offered yet. I tried a grounded or shielded wire. I grounded the shield with no avail. I will try the guard channel next and see if that works. I appreciate the help.

Running the wire perpendicular does not apply so well in my circumstances, but I will investigate.

Thanks, super bummed bout this, next phase is to talk bout returns I guess.

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Re: Touch sensor problem AT42QT1070 always on w/extension wire

Post by adafruit_support_bill »

Capacitive touch is neat, but it often takes some experimentation to get it right. Let us know how the guard-channel works. If you can post a photo or drawing of how your touch sensors are arranged, we might be able to make some suggestions. Adafruit_support_rick has designed some commercial products with cap-sense controls and knows them pretty well.

If it does turn out to be unsuitable for your application, we'll be happy to arrange a return.

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