Introduction

How about a keyboard that does all of that, yet cost about the same to manufacture and integrate as most current types? A keyboard that requires no special parts, materials, or manufacturing procedures other than for regular circuit board fabrication? A keyboard technology that is adaptable to pen-input and touch screen uses? A keyboard technology that will yield an exceptional competitive advantage for the next 17 years? It's hard to believe such a keyboard could exist...

...BELIEVE IT!

Epsilon Group Inc.'s Field Disturbance Input Technology, or FDIT™, simply represents a revolution in the human to machine interface. Conventional capacitive, mechanical switch, rubber dome, and membrane type keypads have now been rendered obsolete. FDIT™ provides a non-contact, solid-state, through-barrier solution that is a cost-effective replacement for even premium membrane technology in any application where absolute reliability, shock resistance, fluid resistance, and survivability are important.

The FDIT™ Keypad is essentially a proximity sensing device. When an operator's finger "presses" a key, the keystroke is detected by measuring the disturbance of an electromagnetic field. No actual contact with the device is required. There are no moving parts. The FDIT™ Keypad is virtually maintenance free, and in most cases will outlast the equipment to which it is interfaced.

The FDIT™ Keypad array itself can be fabricated from ordinary printed circuit board material, shown as element (C) in the above figure. The cells in the array (D) produce a very low energy electromagnetic field (A) through a suitable, rigid facing material, such as polycarbonate or tempered glass (B). When an operator's finger penetrates this field, a keystroke is detected.

Although there are some analogies to the function of a capacitive keypad, the FDIT™ Keypad should not be confused with conventional capacitive products. Historically, capacitive keyboards held the promise of through-barrier design, but exhibited many disadvantages. Among these disadvantages were false triggering, design complexity, and high cost. Epsilon Group Inc. has created a technology that eliminates all of these problems, allowing a highly survivable keypad that can virtually last forever. 

Field Disturbance Input Technology Overview

Capacitive keyboards, as their name suggests, are constructed from an array of capacitors that change value when pressed by, touched by, or at the approach of, an operator's finger. The variable capacitors in the array are constantly measured, and if one changes its value more than a certain amount, it is considered to be "pressed".

The known problems with prior art capacitive keyboards arise because the change of value when a capacitive "key" is touched is very small. Many other factors, such as a change in humidity, can cause the capacitors to change value enough to "press" a key. This false keystroke detection potential in prior art capacitive keyboards caused them to be "fooled" by their environment quite often, leading to their reputation for instability.

Many early capacitive keyboard engineers recognized this problem, and all manner of environmental adjusting mechanisms have been attempted. None were ever very successful; all were cumbersome, complex, and expensive. Those that relied on separate temperature, humidity and other environmental transducers were particularly unsuccessful. It seems that only the capacitive key itself knows exactly how much its value will shift with environmental change.

Some prior art capacitive keyboard engineers tried to incorporate capacitance value magnifiers, or "touch plates" into their variable capacitors. This was in an attempt to cause a wider variation of capacitance when the key was actually touched, "desensitizing" the key to the environment. This did increase stability somewhat, but conversely reduced the key's ability to act as an environmental transducer. When the environment changed too quickly, false keystroke detection still resulted.

Epsilon Group Inc. has solved all of these problems by combining several solutions into one elegant technology.

We start with a new method for measuring capacitors. A method which is uniquely suited to measuring infinitesimally small variations in the magnitude of value of a capacitor. It is sensitive in the extreme. We call it, naturally,

The FDIT™ Method of Capacitance Measurement.*

Next, we have designed a very unique variable capacitor-like proximity detector and environmental transducer. It is very simple to construct, very easy to incorporate into an array, and is very sensitive. It is referred to as

The FDIT™ Sensor Cell.*

We couple The FDIT™ Method of Capacitance Measurement,an array of FDIT™ Sensor Cells, and a common, off-the-shelf micro-controller, together into a keypad device. After exhaustive development, we arrived at the perfect logic means (software algorithm) to determine, based on the measurements of the Cell values, what is a key press, what is an environmental shift, and what is noise. We call this logic means

The FDIT™ Software Algorithms.*

Together, these three attributes, any one of which represents a significant improvement over prior devices, form a truly revolutionary advance in the state of the art of keypad design.

*Patents granted and pending. 

Technology Benefits

Recognizing the trend toward "off-the-shelf" component integration, FDIT™ Keypad was developed in a modular fashion, separating the scanning and key detection modules from the host communication section. So far host communication modules for FDIT™ Keypad have been developed for IBM PC/ATs using the keyboard interface, Neuron™ network interface chips, SPI, full hand-shake serial bi-directional communication, and membrane encoders (for drop-in membrane keypad replacement). Custom FDIT™ Keypad layouts are easily generated, and any host communication software module may be selected. Naturally, a custom designed FDIT™ Keypad can be interfaced to any logic standard, such serial Async communication.

Field Disturbance Input Technology results in many benefits over existing keypads, just some of which are listed below:

• The FDIT™ Keypad is a superior OEM design-in keypad that has significant cost advantages over membrane technology, when all maintenance and service expenses are included, over the life of the product. Cost alone is competitive with membrane technology, when the keyboard encoder is considered.
• There is no physical contact between the operator and the active keypad elements; they need not be even in the same environment.
• Keypad may be hermetically sealed, rendering it impervious to dust, moisture, spillage, and corrosive or explosive vapors.
• FDIT™ Keypad units continually and automatically re-calibrate field sensitivity to compensate for environmental changes and component aging. They are completely unaffected by vibration, humidity, and temperature variations.
• Up to 2" thick glass, polycarbonate, thermoplastic, or other non-conductive cover capability, resulting in virtually bullet-proof survivability.
• Operation is unaffected by protective gloves, yet the FDIT™ Keypad can discern between a finger and a dropped object or projectile.
• Extremely low RFI and EMI emissions susceptibility and radiation.
• Key sensitivity may be altered remotely or locally on a key-by-key basis, which cannot be done with conventional keyboards. This allows operator sensitivity preferences to be set on the fly (by using special key combinations). Multiple key sizes may be mixed together in one matrix.
• Low profile design allows FDIT™ Keypad sensor thickness as little as 0.1 inch (with remotely mounted decoding).
• In many applications, FDIT™ Keypad CPU has as many as 70% spare cycles which can be used to replace existing logic performing other tasks, and minimize total system cost.
• Bidirectional communication with the host allows for remote diagnosis and status reporting. Each sensor cell can be tested for functionality and its status reported back to the host, on demand, with no additional hardware. Applications which require a "heart-beat" or "keep-alive" question/answer to verify system status are supported directly.
• Key to key sensitivity variations due to component tolerances can be automatically detected and compensated in software - a first for this class of products. "Out of ordinary" parametric values can be reported back to the host controller, minimizing production test equipment requirements (reduced number of test points in production, by using built-in A/D capabilities). Final test in production is greatly simplified because of self diagnosis and bidirectional communication capabilities.
• FDIT™ Keypad key sensing module has N key roll-over capability, monitoring the "ON" or "OFF" status of all keys independently. Key detection module is completely independent from the communication module, providing a bit mapped status of all keys in the matrix as the software interface to the communication module.
• Environment calibration routines are very flexible and can be customized for any particular application.
• Extremely low component count for the technology: a 15 key keypad with PC/AT interface can be implemented using just the following active components: 15 pcs. 2N2222 transistors, one 74LS05, one 28 pin, of-the-shelf microcontroller and two 1N4148 diodes.

Applications

• Automatic teller machine keypads or "keyless" security devices that have to be protected from vandalism or tampering.
• Appliances, such as microwave ovens, ranges, and dishwashers.
• Automotive dashboards, military equipment, and aircraft control panels.
• Data entry terminals in industrial environments, where airborne metallic powders and corrosive vapors prevent the use or limit the life of conventional keypads or keyboards.
• Pool-side equipment or automatic car wash systems.
• Heavy manufacturing equipment, where a shock resistant keypad is needed in a small enclosure, such as the control panel of an industrial crane.
• Vending machines, coin operated devices, elevators, and other public-access machinery.
• Point of sale terminals and cash registers, especially in fast food restaurants.
• Keyboards for applications where sanitation or easy "washdown" is of utmost importance, such as medical laboratory or food processing equipment.
• Museum, store window, or other public interactive exhibits or displays where "through window" key actuation would provide a more secure equipment environment with no "external" hardware.
• Can be applied anywhere there is a need for a keypad!

Contact Information

Field Disturbance Input Technology

To find out more, and have a "Hands On" experience with a keypad build using FDIT™ you will need to endorse a non-disclosure agreement (attached, Word for Windows and pdf formats) and forward an original copy to Epsilon Group Inc.

Epsilon Group Inc. stands ready to assist you at every turn. We offer a complete array of engineering design and support services. We can help you at every stage of product development, from product concept to customer support.