Abstract: An adaptive keypad which has one or more keys includes, for each key, a pressure transducer positioned below a semi-rigid faceplate where the pressure transducer has a resistance which decreases as the pressure compressing the transducer increases. The transducer is connected in series with a capacitor to define an RC circuit for each key. Each RC circuit has a charge time proportional to the pressure applied to the key. A time capture circuit initially and thereafter intermittently, obtains the charge time for each RC circuit for each key and computes a conductance value from that time. The initial conductance value is stored in a memory. A comparing circuit intermittently compares the initial conductance value with each subsequent conductance value generated for a key. If the comparison value generated is greater than a predefined amount, a signal is generated indicating that a key has been depressed.

Abstract: A two-axis tilt sensor, or inclinometer (10), uses a spherical reference element (18) floating in an inert fluid (20) and including a magnet (42) to produce an asymmetrical weight distribution. The asymmetrical weight distribution maintains the spherical reference element at a constant orientation with respect to gravity, while the position of the magnet on the spherical reference element with respect to a housing (12) is detected by opposing pairs of Hall effect sensors (22) mounted on the housing. The outputs from opposing pairs of sensors are processed by differential amplifier circuits (80) to determine signals corresponding to the tilt of the inclinometer about the axes.

Abstract: A pressure transducer includes a base ply, a resistance ply disposed on the base ply and at least two spaced apart contacts juxtaposed in relation to the resistance ply whereby at least one of the contacts may be pressed against the surface of the resistance ply. The resistance ply is made by spraying or silk screening a mixture of resin resistive to electrical conduction and a conductive particulate and then curing the composition to form a thin resistance ply having a surface with a multiplicity of micro-protrusions formed by the conductive particulate. The ratio of conductive particulate to resin is such that the mean distance between microprotrusions is greater than about five time the size of the conductive particles. The particles are in the range of about 0.5 to 10 microns and the resin layer is about is 0.4 to 0.8 microns thick.

Abstract: A pressure transducer includes a base ply, a resistance ply disposed on the base ply and at least two spaced apart conductors juxtaposed in relation to the resistance ply whereby at least one of the conductors may be pressed against the resistance ply. The resistance ply is made by spraying or silk screening a mixture of a continuous matrix conductive resin and a stannous oxide particulate and then curing the composition to form a solid resistance ply having a surface with a multiplicity of micro-protrusions formed by the stannous oxide particulate.

Abstract: A multipurpose keyboard incorporating an electronic pressure sensing device, a digitizer pad featuring spatial minimization of a pressure contact area capable of locating the leading and trailing edges of the pressure contact area is described. A processor coupled to the electronic pressure sensing device is programmed to sense when various regions on a simple, fully interchangeable template overlay and the underlying electronic pressure sensing device are depressed. The sensed region is associated by the processor with a particular key identification on the template overlay. The variation of the resistance in the digitizer pad enables the processor to detect the actuation of more than one key on the template overlay at the same time, thereby defecting key rollover. A method of fabrication for a multipurpose keyboard is also described.

Abstract: A digitizer pad apparatus includes at least one digitizer ply where each digitizer ply has a first and a second resistor strip, each with a resistance gradient along its length, oriented in spaced apart relationship. A plurality of conductor traces are interconnected along the length of each resistor strip to extend toward and be interleaved between each other to define a sensor pad region. Each sensor pad region defines a dimensional direction. A shunt ply is positioned to face the sensor pad region in normally non-conducting relationship so that when a selected area is pressed into contact with the conductor traces, conduction between adjacent conductor traces via the shunt ply will occur in the selected contact area. The selected contact area has a first edge and a second edge opposite the first edge along the defined dimensional direction.

Abstract: A digitizer pad includes at least two base plys, each having thereon at least three terminals, a resistor ply disposed between two of the terminals with a plurality of conductors extending from each resistor ply which are spaced apart and interleaved with a plurality of conductors extending from each third terminal. The respective base plys' conducting surfaces face each other and are sandwiched about a nonconductive ply that includes a pressure sensitive conductive layer on each side, the area of which layer covers a portion of the area encompassed by the interleaved conductors on each base ply. The resistor plys and conductors on each base ply are at predetermined angles to those on the base ply, hence the conductors of each base ply form two predefined axes. A voltage source is sequentially coupled, by suitable switching means, across a selected pair of terminals on each ply to measure the selected location along the parameter dimension defined by the terminals across which the voltage source is coupled.

Abstract: A digitizer pad includes at least two sets of terminals where each set has at least a first and second terminal positioned to define a parameter dimension therebetween. A resistor ply is disposed between the terminals of each set. The resistor ply has an electrical contact surface with a resistance gradient profile between the terminals in each set. An output terminal is electrically interconnected to a selected location along the contact surface of the resistor ply. A voltage source is sequentially coupled, by suitable switching means, across a selected subset of terminals in each set of terminals whereby the voltage at the output terminal is a measure of the selected location along the parameter dimension defined by the terminals across which the voltage source is coupled.