Making a Touch Sensor

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    Making a Touch Sensitive On/Off Circuit with Bare Paint and a 555 Timer

    In this tutorial we are going to make a simple touch sensitive circuit using some Bare Paint, a 555 timer circuit, a couple of resistors, a LED

    and a capacitor. The 555 timer is a fun and versatile integrated circuit (IC) that can be used in several distinct ways. There are loads of

    interactive circuits that can be made with this chip, we'll be adding tutorials illustrating more of these projects in the future. Today we are

    using the 555 with its internal flip-flop to sense the change in voltage at two inputs in the circuit. Luckly you don't need to know whats

    happening inside the chip to enjoy the interactions that it affords!

    When you touch the Bare Paint on either side of the gap you connect the circuit through your skindon't worry, the current is so low you will

    not be able notice it. The 555 timer senses voltage change at pin 6 and pin 2, depending on which button you press, and flips the output

    state at pin 3 - turning the LED ON or OFF. By the end of this tutorial you will have painted two touch buttons, with Bare Paint or a Bare Pen,

    that connect to a touch sensitive ON/OFF 555 timer circuit. Once you have got this simple circuit going you are free to get even more

    creative in using the paint to make different graphical touch buttons. Please send your electro-art works to us to put up on the community

    site!

    Components

    Bare Paint

    Paintbrush

    PaperLM555 Integrated Circuit

    Resistors

    Bread Board

    Jumper Wires

    Capacitor

    LED

    Paper Clip Wires

    9V Battery

    http://vsagar.com/2011/12/16/how-ic-555-works-fundamentals-of-ic-555-its-basic-applications/http://www.bareconductive.com/store/products/bare-painthttp://www.bareconductive.com/store/products/bare-painthttp://www.bareconductive.com/store/products/bare-painthttp://www.bareconductive.com/store/products/bare-painthttp://vsagar.com/2011/12/16/how-ic-555-works-fundamentals-of-ic-555-its-basic-applications/
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    Painting the On/Off Touch Buttons

    Before you start to paint your buttons onto a non-conductive surface, such as paper, think about what form you would like the graphic to take.

    You can think of the 'button' as a line of paint with a gap and at that gap you connect the circuit with your finger, thumb or other body part. So

    make sure it is narrow enough for this. A very small current, imperceptible to a human, flows through the paint and across your skin when

    you bridge the circuit over the paint-gap.

    Second, paint your decided button graphic onto your surface with Bare Paint and a paintbrush. I have done this on paper and used a thin

    piece of masking tape to ensure a clean thin break at my touch points. Below is my finished pair of touch buttons after being left to dry for

    several minutes. I have made sure that the starts of my lines come close to the edge of the paper so that they can be reached by a paperclip.

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    Placing the Components and Connecting the Circuit

    The next step is to assemble the simple circuit (pictured in the image below). Take a good look at the breadboard schematic and make sure

    you have connected the circuit up correctly. You can download a copy of the breadboard schematichere.

    http://www.bareconductive.com/file/555-touch-schematic-24-sept-pdfhttp://www.bareconductive.com/file/555-touch-schematic-24-sept-pdf
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    Adding the Paperclip Wires

    Once you have your circuit setup on your breadboard you can place your paperclip wires in the tracks indicated in your schematic and in the

    images below. Take a look at our connecting tutorial which shows you how to make these cool prototyping wire - and other interesting ways

    to connect to Bare Paint.

    http://www.bareconductive.com/connectinghttp://www.bareconductive.com/connecting
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    Testing

    You can test it by first touching the blue paperclips together to turn the LED ON and then touching the yellow pair together to turn it OFF.

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    Connecting to Bare Paint

    Now you can connect them to your touch buttons using the paperclip ends of the wires. Connect the blue wires to your ON touch button and

    your yellow wires to your OFF touch button. You can simply place your finger, thumb or other body part at the gap to control you LED! It's

    that simple and ultimately very satisfying!

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    Completed Circuit!

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    If this is working for you, you can now start experimenting with creating more interesting painted buttons with your paint - they don't even

    need to look like buttons. Try using vinyl cutouts as stencils or even try screen printing if you have access to the equipment. Check out these

    cool painted button below! Make sure to send in your crazy work so we can post it on our community wall - email us at

    [email protected].

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