Tag Archive for: projective capacitive

I need to use the most dependable touch screen for our new product, which one? – Gerry, Mooselookmequintic, ME

Hey Gerry,

(BTW, is that really your town?), I like questions where I don’t have to give a wishy-washy answer. First, for the neophytes amongst you, there are five commercially viable touch technologies, from a list longer than the number of letters in your city….they are, Resistive (four types), Surface Capacitive (two types), Infrared, Surface Acoustic Wave (SAW), and Projective Capacitive or, as we affectionately call it, P-Cap, and you know as iPhone-type. (Those of you with corner-cameras, fibers on the edge, and in-cell systems, come back when you have real sales.)

Before I give you the answer, as the cognoscenti amongst you know, any touch technology will work for 80% of the applications, so those of you with the projects that need a specific type, dependability may not be the best question to ask. But the answer to which touch screen is most likely to be running in the morning, is, TA DA, P-Cap.

Why is it that Touch International has built millions of P-Cap touch screens over the last four years and not one has come back for non operation? The reason is that projective technology has nothing to wear out, the place you touch is just glass, which has a 9H scratch resistance (yeah, sapphire glass is better, but you can’t afford it), and the electronics are simple. With p-cap, the sensors are typically made the same way the safety glass windows in your car were made, so it is tough to break, which gives this technology the edge on the runner-up in the dependability category, which is SAW. The electronics are simple and minimal, which gives p-Cap a bigger edge over the third place (dependable touch) technology, which is infrared and its dozens of expensive emitters and phototransistors.

Touch International makes p-cap sensors from 1.8 inch to 22 inch, so, if the most dependable touch technology is your first priority, Gerry, my man, you know how to answer your cranky boss…just tell him P-Cap.

Until next time,
Touch Guy

It was with great excitement that I received my projective capacitive multi-touch kit from Touch International. My guidelines for our vendor were to find a touchscreen with multi-touch support and support for security glass. I’ve seen that there is no driver for this touch screen to support multi-touch. And on the other hand we tried to put a glass layer in front of the touch panel and it didn’t work. Another problem we are facing is that if the touch-panel comes near the lcd-panel the touch coordinates are wrong. What gives?

– Daniel Amesberger

Well, TouchGuy hangs his head in shame for letting you down. While the real world performance is fantastic, It turns out that this new-fangled projective capacitive (p-cap) touch is not quite so plug-and-play as the plain-old-resistive-touch. All touch technologies have their idiosyncrasy—resistive touch needs to be calibrated to the display, IR requires that the beams and receptors are aligned, SAW has special bezel mounting requirements, and DST even requires “certified installers”. In its exuberance to ship the p-cap samples to customers, my guys and ladies did not provide much of (read, practically nothing) in the way of a manual. Touch is working hard to prepare the support you need to do your evaluation. For now, here are some things to consider:

1. Although the sensing layer is sealed inside the glass or plastic (which is why it never wears out), there is a front and back. You really cannot tell which is which, so we will be marking the front side..

2. Most of our sensors come complete, so if you want to put your own cover glass on the sample, you will need to make sure you are putting it on the front, and you will need to reset the controller so it can reset the values for the new glass. Normally, cover glass cannot be more than 3mm thick. If you need the cover glass to be thicker, you need a special version of the controller.

3. If you change the cover glass, you may need to use our new wiz-bang GUI control program to reset the sensitivity. This utility will be available next week.

4. When p-cap electronics start-up, a quickie calibration occurs. Normally the sensor will be attached to the display, but if it is not, sometimes picking the sensor up and moving it will affect the sensitivity; note that this only applies when the sensor is moved without being attached to the LCD.

5. In some rare instances, there is a big ‘ol metal plate under the desk or table. A big metal plate will negatively affect the sensitivity.

6. We have multiple controllers—single touch, multi-touch, all-points-addressable, proximity sensing—lots more actually, so you need to make sure you have the one you want.

7. Demonstrating multi-touch requires a multi-touch driver, so you need to install it or you will just get a single touch. When Windows 7 is released, no driver will be needed for USB operation.

Until next time,
Touch Guy