Previously published in the October edition of ECE Magazine, this article written by Helen Francis from Atmel summarizes test results using gloved hands to operate capacitive touch sensors. The article stipulates that the subject must be dealt with on a case-by-case basis, but says that in general, it is possible to use touch panels as a human-machine interface, even in environments where gloves must be worn. Read the full article to learn more.
I guess you know water can be a lot of trouble for touch screens. The most vulnerable is SAW which stops dead in its tracks, to the least vulnerable, resistive touch. Resistive can be sealed so that water does not get in between the PET and glass layers which allows for better performance with water.
The ultimate irony is that most touch screens work because humans are just big bags of salt water and the water in our bodies serve as the primary activating mechanism. The problem is that the touch screen must distinguish between you, the big salt water bag, and the salt water puddle. (There is one rare form of an acoustic touch system than operates in a fully submersible ocean environment, but Touch Guy will ignore that one for now because it is made by a competitor).
So Touch Guy, still the SUPER-CHAMPION of projected capacitive needs to come clean on water and multi-touch. And if you follow Touch Guy, you know his answer to most questions is, “it depends.” In this case, it depends a whole lot on which sensing IC (Integrated Circuit/Chip) you use. Most ICs will invariably yell, “I quit!”, when it gets a lot of water on it – check out your iPhone sometime. The best IC could be saying, “I love water!”, and works really well. The water-loving IC will even work covered in distilled water, but as the salinity increases (as would be the case on the ocean) a salt spray is as far as you can take it. So your projected capacitive fish finder will work on the local lake in a light rain, but bow-busting 40 foot ocean waves are probably a little much.
Still need to survive the salt water wave and keep on multi-touching? Then the Resistive MARS technology is the one for you. Silicone-sealed behind a water tight bezel, this touch screen can take that salt water puddle and keep on touching. Add sunlight readable filters to the MARS sensor and you are ready for a jaunt around the continent on the bridge of your new yacht!
Until next time,
Wanting to keep things simple, Touch Guy’s answer is “No and Maybe” (this is my new alternate answer to the usual, ‘It depends’). For those of you using a USB-connected system, the touch screen will look like a mouse to your software and because virtually all software works with a mouse, nothing is required. For Windows 7, the touch screen will look like a digitizer or several digitizers to accommodate multi-touch (one for each touch occurring at the same time) and nothing new is required to do all of the cool gestures like pinch, rotate and shrink. Similar multi-touch support is available for Linux operating systems and some versions of CE (though XP embedded comes with fewer headaches). The technical term for this magic is HID Compliant (HID=Human Interface Device) or in the case of Win7, Windows 7 Tablet Compliant. All of Touch International’s USB projected capacitive systems are compliant and will work without having to do anything extra.
The “Maybe” answer comes in to play when systems still run on serial (RS232) connections which require a driver to allow the touch screen to communicate with the software. A touch screen generates an X and Y coordinate (and in some cases a Z). The driver looks at the touch coordinate and then looks at the “hot spot” or the place where the mouse cursor was left on the screen. Next the driver moves the mouse cursor with up/down and right/left “mickeys” to the location of the touch and issues a mouse click. And Jiminy Christmas, the touch works with any software! Touch drivers also allow you to control other things such as calibrating the touch screen to different size displays, controlling how hard or light you have to touch the screen, enabling right button clicks and eliminating the mouse cursor from the screen.
Happy Holidays and remember… my touch screens make great gifts!!
Until next time,