Force invariant touch sensitive actuator

In a control circuit for operating an electrical load in response to an output signal from a touch pad, said touch pad comprising an elongated manually touchable resistive area which produces an output signal at an output terminal, said signal representative of the location at which the touch pad is manually touched, said control circuit including a microprocessor having an input connected to said output signal and producing an output for controlling said load in response to the manual input to said touch pad, the improvement comprising a filter capacitor connected between said output terminal and a ground terminal to define a resistive-capacitive circuit with the resistance of said touch pad, said resistive-capacitive circuit characterized by a time constant and being adapted to prevent large transient voltage changes due to low pressure touches of said touch pad, said filter capacitor both charging and discharging through said touch pad.

In a manually operable control structure for producing an electrical signal dependent on the location at which a touch screen is touched;

• said control structure comprising a resistive touch screen having a control voltage connected to terminals at its opposite ends and an output terminal which is connected to said touch screen at the location of a local manual pressure applied to said screen by a user;
• a microprocessor having an input connected to said output terminal and producing an output related to the position at which said screen receives said local manual pressure;
• the improvement which comprises a filter capacitor connected between said output terminal and a ground terminal and defining an RC circuit with the resistance of said touch screen between said position at which said screen receives local manual pressure and one of its said terminals, said filter capacitor both charging and discharging through said touch pad.

A process for generating an operating signal from a resistive touch screen in which an output voltage on an output terminal thereof is related to both the location on the screen area which is touched by a user's finger and to the pressure of the touch;

• said process comprising the production of a usage detection signal in response to the touching of said screen at any location on its surface and the production of a position signal in response to the location at which the screen is touched, and applying said usage detection and position signals to a microprocessor;
• said microprocessor producing an output signal to a circuit to be controlled only when said usage detection signal is present and said position signal is also present at the end of a predetermined sample interval,
• wherein the position signal is substantially responsive only to the position of the point actuation on the touch sensitive front surface of the touch sensitive actuator and the usage detection signal is representative of whether an actuation is presently occurring, said usage detection signal having a faster response time than said position signal.