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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