Sophisticated industrial controls, chip and PIN commerce, access control systems and high-end consumer goods are among the emerging applications that demand enhanced performance from electronic keypads. Demands include sealing to ingress standards as high as IP65 to withstand dusty or wet environments on factory floors or outdoors, high impact resistance in public access or security-related applications, as well as long life and low maintenance for cost-effective remote deployment. In other situations, such as upscale white goods and other high-value consumer products, extremely thin keypads are required, to present an attractive, high-tech image.

Keyless keypad?

Traditional keypads, which depend on mechanical switches, cannot meet many of these modern demands for high reliability and longevity, small size and ease of assembly. Special construction to seal against moisture or particle ingress adds cost to the solution, and all mechanical keypads are prone to malicious or accidental damage.

Eliminating the mechanical switches, which are the weakest point of the keypad, is a desirable solution in the most demanding applications. One way to achieve this may be to implement touch sensor technology. A touch sensor invites users to make selections similar to the way a keypad behaves. Some applications may even depict a keypad on-screen, such as the calculator function of a PDA. However, most established touch sensor technologies also suffer from some significant limitations and failure mechanisms. For example, a resistive touch sensor overlay is highly susceptible to wear and damage, and is therefore generally unsuitable for industrial and outdoor environments.

A traditional capacitive touch sensor, on the other hand, cannot effectively detect a touch if the user is wearing gloves. This would be a serious disadvantage in industrial applications or food preparation, for example, where operators are highly likely to be wearing protective gloves. Its suitability for outdoor commercial applications, too, is also compromised. In addition, both of these technologies tend to drift over time, requiring periodic recalibration or adjustment.

Keypad control

ZYSWITCH technology can be customized for keypad arrays to meet a wide range of requirements from a standard numeric keypad to application specific implementations with a menu-driven selector.

However, a new control strategy now allows the PCT touch sensor to operate as a standalone panel, featuring software-defined touch active areas acting as individual keys. The keys are printed directly onto the surface of the glass. When a touch is detected in any of the touch active areas, it can be decoded in the same way as a key-press on a standard keypad; for example to present a BCD serial signal to the host system. Alternatively, a custom output coding may be generated if required. Hence touch sensor technology can be used directly in keypad applications, and integrated using familiar techniques and interface architectures. Signal conditioning such as switch debouncing is also performed inside the keypad controller, with no sophisticated drivers or additional software required in between the keypad and the host system.

Using this new ZYSWITCH technology, Zytronic is able to quickly customize a keypad array (see photo) to meet a wide range of requirements from a standard numeric keypad to application specific implementations such as a menu-driven selector or a control panel for an industrial machine. Leveraging the company’s background as a producer of specialist glass products, Zytronic also has competencies in-house to print decals directly onto glass, thereby enabling unique and highly finished products to be produced cost-effectively and within short delivery times.

A ZYSWITCH keypad is also a very low-profile device. Its thickness is essentially defined by the thickness of the front and rear glass panels specified. The controller is mounted directly on the rear of the panel, as in the ZYTOUCH touch sensor. This low-profile attribute combines with non-mechanical key activation to create a flat and unobtrusive panel that can be easily installed without the complex cutting and drilling frequently required to install a conventional or membrane keypad.

Technology transfer Transferring touch sensor technology to keypad applications can potentially unlock extra performance in the most demanding modern applications. However, conventional resistive or capacitive sensing methods using a screen overlay do not fully eliminate the mechanical switching action that is the weak point of current keypad implementations including membrane keypads.

A PCT sensor solution can bring to keypads the same advantages it has enabled in larger touch sensor products, including durability and the ability to function outdoors, in all weather. Following the arrival of a purpose-designed keypad controller, a keypad displaying security and longevity comparable to the best PCT touch sensors can now be integrated in much the same way as a standard switch-based or membrane keypad.

For more information email: mark.cambridge@zytronic.co.uk