TouchControlPanel
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Copyright 2009 Jonathan Oxer
Copyright 2009 Hugh Blemings

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| This project is featured in the book "Practical Arduino" by         |
| Jonathan Oxer and Hugh Blemings (Apress, 2009). More information    |
| about the book and this project is available at:                    |
|                                                                     |
| www.practicalarduino.com/projects/touch-control-panel               |
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Small 4-wire resistive touchscreens are now amazingly cheap: they are
produced in such enormous quantities for mobile phones, PDAs, and
particularly handheld games such as the Nintendo DS that they can be
bought brand new for under US$10.

Larger touchscreens are also rapidly falling in price. The popularity of
netbooks with screens between 7" and 10" in size has resulted in a
healthy market for touchscreens that can be retrofitted to them and
plugged into an internal USB port. Despite the fact that they come with
control electronics and a USB interface those screens are also
predominantly 4-wire resistive devices, so if you dump the control
module that comes with them and interface to the screen directly you can
have a 10" touchscreen on your Arduino! And if you want to go even
bigger there are often 15", 17", and 19" touchscreen kits available on
eBay for under US$150.

Note however that what is advertised as a "touchscreen" is not actually
a complete screen including an LCD. It's just the transparent glass and
plastic panel that fits onto the front of an appropriately sized LCD so
the CPU can detect the point at which it is being touched. If you want
your Arduino to display information on a screen and let you select or
control it by touch you'll have to do a bit more work to set up the LCD
that goes behind the touchscreen overlay.

Even on its own though a touchscreen is a very handy device. They're
incredibly thin and can be mounted over the top of any flat surface, not
just an LCD, so they're great for creating little custom control panels
with the "buttons" printed on a sheet that goes behind the touchscreen.
All you have to do is map the buttons to X/Y coordinates and your
Arduino can figure out which button is being pressed by matching the
coordinates. Of course your control panel could represent anything, not
just buttons. You could have a slider on it to select volume or
temperature level by touching somewhere along a scale, or it could be a
plan of a house so you can control lights in different rooms by touching
the correct part of the floorplan.

In this project we mount a Nintendo DS touch screen on a blank
electrical wall plate to create a touch-sensitive light switch that can
link to a home automation system via web services.