Touch Sensor break out board

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michaeltsjr
 
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Touch Sensor break out board

Post by michaeltsjr »

recently purchased 2 - AT42qt1012 capacitive break out board that will be connected to a 2n2222 npn xristor to drive 16 ma of leds. Vdd used is a 3 volt coin cell. the basic overall ckt works HOWEVER >>>> After toggling the output LED on / off or active high / low via the 2n2222 circuit the I allow the circuit sits idle and after many minutes the device seems to automatically turn on. CAN ANY INPUT BE PROVIDED THAT WOULD ALLOW ME TO RECTIFY THIS PROBLEM????

PLEASE HELP AS THIS IS THE PROTOTYPE THAT WILL BE USED IN A INTERESTING AND UNIQUE INDUSTRY.

I look forward to hearing back from anyone that can help.

thanks MTJR

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adafruit_support_bill
 
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Re: Touch Sensor break out board

Post by adafruit_support_bill »

Are you using the on-board sensor pad only, or do you have a custom sensor attached?
Are there any nearby potential sources of interference?
If you post a photo of your setup, we'll see if we can spot anything suspicious in your setup.

Also note that these are self-calibrating at power-up. It is best to keep hands and such away from the sensor as it is calibrating.

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michaeltsjr
 
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Re: Touch Sensor break out board

Post by michaeltsjr »

Bill I don't have a device pic just yet. however I can tell you this. Using the Atmel device on the touch board supplied by Adafruit it would have been convenient to have a component layout of the board so I could tell which components are already in the circuit that Atmel suggest one use in order to interface to it. As far as the configuration I did have a lead to the touch sensor PC pad nearest to it, I have completely removed it and the problem still exist. I am not currently near any device or object that might cause some interference. In the future this device may be near a DC motor.

The timing when this problem occurs is fairly consistent, 10 to 15 minutes and the device turns on by itself. Atmel suggest some small capacitance to be added to 2 to 50 pf and a Rs resistor to pins 3 and 4; are these already on the breakout board? My circuit is this>>>, I have a 2N2222 base through an approx. 3Kohm resistor tied to the output pin; the collector is on the low side of an LED and the Anode is tied to Vdd (which is 3vdc). The emitter is tied directly to ground. Again the circuit works, meaning it toggles after start up off /on and off however to toggle on again I must wait a count of 15 to 20 seconds in order for it to come back on. This is ok with me and this application, however the self turning on isn't.

Not sure if any of this helps, if not I will make a neater drawing of my circuit with pic and supply. I really want to use this breakout board as it provides the solution to meet my goals for this overall product. If this above sheds additional light on the issue I will be very much appreciated. Perhaps you could supply a configuration that you all there think might work. Also one of future applications will be adding a timing circuit to Auto off the LED's. The Atmel data sheet is a bit sketchy on accomplishing this, again this is not needed at this time.

Mike TS

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adafruit_support_bill
 
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Re: Touch Sensor break out board

Post by adafruit_support_bill »

I don't see the board files in Github. I'll see if I can track down the schematics for you.

From what you describe, the circuit sounds like it should work. Sometimes a photo helps us spot the unexpected problems.

MTSJR123
 
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Re: Touch Sensor break out board

Post by MTSJR123 »

To you all there or Bill, It seems I found the issue and the device is working beautifully. It seems during the prototype build I had some compoents mounted with long leads and thus they were picking up some noise causing the device to turn on. I have placed this board with the touch device operating near a DC motor and no negative results. I am very pleased with its operation. I have one question at this point, can the breakout board be mfg'ed without the touch pad but allow the opportunity to still use and external touch pad??? This would make the board smaller in overall size for ease of final ass'y in manufacturing.

Thanks so much again and look to you all in the future for more volume of product.

MTSjr

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adafruit_support_bill
 
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Re: Touch Sensor break out board

Post by adafruit_support_bill »

We don't have any excess capacity for a custom run of boards. But it does look like you could cut off the top 2/3 of the board. Other than the touch pad, the only component above there is the indicator LED.

Image

MTSJR123
 
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Re: Touch Sensor break out board

Post by MTSJR123 »

Thank you for the encouraging info. I now assume that cutting the board and removing the touch pad and LED (didn't need that anyways) would allow me better positioning of the required components for my product. Again Thanks, hope you are right. Mike TS

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Franklin97355
 
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Re: Touch Sensor break out board

Post by Franklin97355 »


MTSJR123
 
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Re: Touch Sensor break out board

Post by MTSJR123 »

Thank you again. you all have been very helpful...

Mike S

MTSJR123
 
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Re: Touch Sensor break out board

Post by MTSJR123 »

Bill or Mike we have communicated in the past last year, I have a question that needs an answer that I seem to not recognize from the Data sheet of the AT42QT1012 device. I have built now about 20 PCB's with this device on it and well something I neglected to consider at the time and need some feedback. This project is using a single CR2032 button cell.

The question is this >>> When the device is in the OFF state, what is the sensor device drawing from the battery? Is there any way to completely shut the device off so as to not draw current from the battery???

I look forward to your response via email. thanks

Mike TSJR

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adafruit_support_bill
 
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Re: Touch Sensor break out board

Post by adafruit_support_bill »

Current draw is voltage dependent. See page 23 of the data sheet for current draw info: http://www.atmel.com/Images/Atmel-9543- ... asheet.pdf
The only way to shut it off completely is to cut power to the device.

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