Tag Archive for: p-cap

Hey Touch Guy, I’m working on a sort of digital signage / kiosk type application that will hopefully be everywhere from hotel lobbies to office buildings. The plan is to start out around 32” and eventually grow to 60”. I’m thinking I want Projected Capacitive for the touch screens for all the usual reasons , but people are telling me optical touch is the way to go due to size. So who’s right and what’s the best? PCAP or optical? – The Sign Guy

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Hey Sign Guy,

The big ones, usually defined as over 32 inch LCD’s, have long been the domain of optical systems with an occasional sighting of an acoustic (external and internal noise generator) or surface capacitive sensor, as well as a smattering of the other touch technologies. Optical is defined as IR beam or corner camera type. Recent advances in optical touch systems have added the ability to do multi-touch which had been one of the drawbacks. Frankly sign guy, optical is your best choice today. But do not sign any long term commitments. The market wants p-cap with pen for large format displays. Why, you inquire? The same reasons the small display guys want it….low cost, high reliability/durability, multi-touch, gestures, and good image quality – in addition to the twelve other things people like about the technology. The holy-grail of big formats seems to be white-boards (think every school room and meeting chamber) as opposed to the slow growing digital signage market (for touch displays). But, as Touch Guy has pointed out, p-cap has changed the sleepy old days of resistive touch manufacturing to major advances every six months…..that 82 inch, $35,000 p-cap touch panel you saw at the trade show last year will be in your budget within 12 months. Already 32 inch p-cap is common and cheap, due to advances in the materials, IC’s, and manufacturing techniques. Passive pen is not quite ready for the big ’uns yet, but when it is, Touch Guy advises you buckle your seat belt.

Until next time,
-Touch Guy

“Hey Touch Guy, why can’t the military use projected capacitive?” – Ready, aim, fire!

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Whoa, simple question – complex answer.

First, the “military” does use projected capacitive (p-cap for short), and purchases a huge number of iPads and iPhones. But I think your question is, “Can the military use p-cap in a battlefield environment.” Yes, there are problems that have slowed the introduction of p-cap. Here are a few that need to be addressed, and are being overcome.

Most of the armed forces are very careful about generating EMI that could be detected by the bad-guys. P-cap, you will recall, works by having a human drain capacitance from the touch screen at the touch point. For multi-touch, that means lots of small fields are created on the TouchGuy_Basicsurface of the touch screen. The fields are quite small, and inconsequential compared to the EMI from radios that are in most devices, but they are still there. TI has been able to tune the frequency to meet

EMI is a general problem, but it’s not alone in the obstacles p-cap must overcome. The Navy and Coast Guard, not surprisingly, want rain and sea-water immunity. Solutions have been developed in the electronics to compensate for tap and rain water. But sea water, because it is more conductive, is a more difficult matter because it spreads a conductive film across the touch area, and when a finger is touched to the screen the capacitance is drained from lots of points which confused the touch electronics. TI has developed a new total immunity sensor that works both mechanically and electrically to provide immunity to sea water.

Both the Army and Air Force require gloved finger operation. For most flight applications, the gloves are thin-enough that p-cap is a great choice. However, for some Army applications, the gloves are bigger and thicker and an accurate touch is more difficult…Touch Guy does not think this is a real issue because if the gloves are so big and bulky, how can you touch a small point anyway?

Impact, and the resulting breakage, is another issue, as most p-cap touch screens are made from glass. There is also a weight issue in using glass. The obvious solution is to make the p-cap sensor completely out of plastic or some form of acrylic substrate, however, plastic can scratch in some environments. Technology to the rescue, there are new transparent hard-coats for plastics that can approach the scratch resistance of glass.

In conclusion, Touch Guy believes the real roadblock preventing the introduction of p-cap into the battlefield isn’t the touch sensors themselves, but the lack of new programs that would make use of the latest and greatest touch technology has to offer.

Remember, I come in peace! – Touch Guy