Hello, I'm a newbie to arduino and have just purchased my first arduino mega for a school project.
I would like to ask whether it is possible to interface a touch screen display for issuing commands ( such as to turn on the motors ) to the arduino board while it is underwater.
Thanks in advance.
What will be under water?
The Arduino board or the touch screen ?
What is the distance between the Arduino board and touch screen ?
What sort of touch sensor?
Capacitive is going to be tricky under water, and pressure-sensitive may not work at depth (or rather, it will "work" all the time!)
My project is to construct an autonomous underwater robot, so the arduino board will be inside the chassis with an opening to expose the touch screen. The distance between the touch screen and arduino board will be around 5 inches I believe.
Not too sure which type of touch sensor to use, any recommendations if the depth is around 5 feet max?
Thanks in advance =)
Well, there are only really two types of touch screen: capacitive and resistive.
Capacitive wouldn't work under water, and they're more expensive anyways, which leaves you with resistive. You can pick up a small resistive touch screen (NDS) for ~5 bucks shipped. If you assume this is pure (or relatively pure) water, then pressure increases at ~.44 psi per foot. That means that the NDS touch screen would have ~2.2 psi on it. I assume that would probably render it useless (as the water would press the screen for you!).
Not to mention that as the touch screen is about 4.3 in2, you have a total of ~9.5 pounds of force on the screen. Easily enough to break it in half unless the submersible is well pressurized.
I did a little more research into capactive and resistive touch screens.
My main objective for the touchscreen is to turn on / off the underwater robot on land, and at the same time for displaying parameters (only) underwater.
Hence is it possible to configure the arduino mega to reject any non stylus inputs to the touch screen ( resistive ) to allow it to be used underwater after launching ?
At the same time, I will be using interrupt fuctions that will reactivate the touch screen based on my other outputs from sensors, eg. pressure etc.
If the input surface of the touch screen is exposed underwater, is there any methods to counteract the ~9.5 pounds of force?
Yes, just pressurise the interior to the same pressure.
Have you thought about an optical touchscreen?
One thing to keep in mind is that when people are talking about a "touchscreen" in the context of something like a Nintendo DS touchscreen, there's typically no actual screen included with it! The NDS touchscreen mechanism is a clear glass substrate with the layers of the touch mechanism built up on top of it, and that assembly is then fitted over the top of an LCD so that you can see the LCD through it. It's not part of the LCD itself though. You can see an example of a NDS touchscreen being used without an LCD in this video:
In that video you can see I'm just holding the "touchscreen", but there's no "screen". So ...
If the input surface of the touch screen is exposed underwater, is there any methods to counteract the ~9.5 pounds of force?
... you could just mount the touchscreen assembly onto a flat sheet of some suitable material (strong plastic?) on the outside of the submersible and seal around it with silicone. It would end up something like this:
http://www.practicalarduino.com/projects/touch-control-panel
I really suspect you're going down the wrong track here. My suggestion is to use an LCD behind a bit of perspex for visual display, and track down some waterproof push-buttons for menu selection. It'll be much simpler and more reliable than trying to make a submersible touchscreen.
Freetronics: www.freetronics.com
Thanks for clearing up my doubts, I used to believe that the touch mechanism comes with the LCD display kit when it comes to Nintendo DS touchscreen.
My question is whether it is possible to expose the LCD display kit with touchscreen mechanism underwater without any plastic casing housing the touch mechanism.
Regarding pressurizing the interior of the section, I intend to expose the " touch mechanism " with the LCD display panels outside of my submersible , is it possible in this context?
Thanks in advance