Intro: Making a Touch Sensitive On/Off Circuit With Bare Paint and a 555 Timer IC
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 input in the circuit.
When you touch the Bare Paint on either side of the gap you connect the circuit through your skin – don'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!
Step 1: Components
For links to purchase these components visit our tutorials page at: http://www.bareconductive.com/555-touch-circuit
LM555 Integrated Circuit
Paper Clip Wires
Step 2: Materials
The first step is to gather the appropriate materials mentioned above. To make this nifty circuit you will need:
1. A jar of Bare Paint, paint brush and paper, or use a Bare Pen
2. A 330 Ohm resistor, two +-2.7 Mega Ohm resistors (make sure it is sufficiently large for greater sensitivity), one 10nF capacitor (0.01uF = 10nF = 10 000pF) and a LED
3. Some wire to make your paperclip wire connectors (see Connecting to Bare Paint for how to)
4. Solder-less breadboard and some jump wires
5. Some paper or other non-conductive material to apply the Bare Paint
6. A 9V Battery and a battery clip with wires.
Step 3: 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 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 lines come close to the edge of the paper so that they can be reached by a paperclip.
Step 4: 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 schematic above.
Step 5: 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.
Step 6: Circuit Diagram and Breadboard Schematic
Step 7: 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.
Step 8: 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. Now you can simply place your finger, thumb or other body part at the gap to control you LED! It's that simple!
Step 9: Completed Circuit!
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 firstname.lastname@example.org.