Outdoor kiosk project

Requirements:

The customer requested a 5 wire 15" resistive touch screen that could be operated outdoors.

• resist an impact force of 5 joules
• IP 67 sealable
• unaffected by dust, rain, leaves, stickers, chewing gum
• compliant to ASTM-F-1598-95
• more the 100 million touch events per point
• high scratch resistance ( especially coins )

Technology decisions

There are so many technologies out there that is was not that easy to pick the right on.

• Surface capacitive was our first choice but could not satisfy our customer because the scratch resistance was not good enough. They did some scratch tests and to our surprise even with a coin the outer ITO layer could be scratched off.

• SAW could not meet the requirements for long lasting usage without service. Dust and dirt resistance was not acceptable. There was another effect the customer recognised. Bugs where attracted by the light in the night and triggered constant random touch events and affected the lifetime of the TFT seriously.

• Infrared was to coarse in resolution and had the same "bug effect" like SAW

• Regular 5 wire resistive was not an option at all because is matched the requirements of the customer at least.

• ULTRA resistive touch screens were the last option that the customer considered. After the tests the customer was really surprised because ULTRA fulfilled every aspect of their specification without any problems.