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SOLVED - Capacitive Touch Sensor w/ GPIO

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Monica Knutson
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So... we have a Capacitive Switch that we want to use to trigger a single GPIO [0] input.  We are powering it off of the 3.3VDC/GND on the Phoenix connectors.  

XT243 is the model BrightSign we are using.

The switch is LOW until pressed and then sends HIGH.  This is reverse of what the BrightSign is expecting apparently because it just triggers all by itself without any input touches on the sensor.

How do we reverse the input so it accepts a HIGH vs a LOW?  Please note that all of our Radio Shacks are gone and there are no electronics hobby stores within about 60 miles of us.  

Advice and guidance welcome!

Cheers,
Monica

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  • 0
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    Bright Scripters

    By defaul the player responds to signal going low but you can change that to going high.
    In BA double-click the GPIO event under Trigger Event on Button, change from Down to Up.

  • 0
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    Monica Knutson

    Thank you, we tried that as well but to no avail.

    The capacitive switch has three wires going to it... not like a latching relay PIR.  

    GND, +Vcc (3.3VDC) and then GPIO 0 goes to the OUT from the capacitive switch.

    GPIO 0 pushes 3.3VDC back to the BrightSign on trigger (HIGH) and off trigger multimedia measures at 0.119VDC.  I tried an inline resistor (680ohm) but that just increased the VDC to about 1.2VDC when not triggered so it has the opposite effect.  My guess is because of the pull-up resistors that are in the BrightSign on the GPIO.

    It just loops and loops without any touch.  The test I am using is very simple:

    1. State 0 (home) is just a black PNG 1280x720.  It times out after 5 seconds to State 3 which is another black PNG.  That is our settle in period for the capacitive sensor (only requires 100ms but adding pad).
    2. State 3 times out after 5 seconds to State 5 which is another black PNG.  I do this just in case the state needs to "refresh" (or if they have multiple screensavers they want to do down the road).
    3. Both State 3 and State 5 have GPIO 0 Trigger Events with Button UP that go to my video which is on State 1.  Video state ends after Media End event and returns to State 3 to resume the loop between States 3-5 until GPIO triggers it to play again.

    Any additional help is highly appreciated!

    Cheers,
    Monica

  • 1
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    Monica Knutson

    Hello all!

    After dusting off my Electronics manual (literally from 1997) and weeding through my electronic components I came across an NPN TIP120 RadioShack Darlington Transistor and some resistors.  Am proud to say challenge overcome!

    For anyone who also needs to use one of the Capacitive touch sensors from SparkFun or AdaFruit that use output pins that go HIGH here is the recipe:

    1. Setup the GPIO button event to Down (not Up)
    2. Build a circuit as per the attached image (details below)
    3. Run the presentation and have fun activating from touch objects

    CIRCUIT REQUIREMENTS:

    • NPN transistor (I used a TIP120)
    • 10K resistor
    • Capacitive touch sensor board (here or here - they both use the same IC chip)
    • Breadboard or PCB that you can solder to (like this)
    • Wire bits (22ga)

     

    I used an XT model with the new Phoenix connectors, so those are the pin outs below for the BrightSign.
    Pin 1 - GND
    Pin 2 - 3.3VDC
    Pin 3 - Button 0 INPUT

    • OUT comes from the "OUT" pin on the Capacitive Sensor
    • GND also goes to the "GND" on the Sensor Board (not illustrated)
    • 3.3VDC also goes to the "VOD" on the Sensor Board (not illustrated)

    On the circuit you're building take:

    • the GPIO input and attach to the Transistor Collector
    • GND to the Transistor Emitter
    • OUT through the 10K resistor to the Transistor Base

     

     

     

    Good luck and happy proximity touching!

    Cheers,
    Monica

     

     

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