Patent ID: 8253072

Claim:
A data input device for heating at least one surface of the data input device, the data input device comprising: a heating circuit comprising: a heating apparatus; and a relay comprising: a first terminal connected to a power supply; and a second terminal grounded via the heating apparatus; and a temperature control circuit comprising: a variable resistor comprising a first fixed end, a second fixed end grounded, and a sliding end, wherein a determined temperature of the data input device is set through adjusting the variable resistor; a second resistor; a first diode comprising: a cathode connected to the first terminal of the relay; and an anode connected to the first fixed end of the variable resistor; and an integrated circuit chip comprising: a power pin connected to the cathode of the first diode; a control pin connected to the sliding end of the variable resistor; at least one input/output (I/O) pin grounded via the second resistor; and a ground pin grounded; wherein upon the condition that a temperature of the data input device is lower than the determined temperature, a reverse resistance of the first diode is high such that a voltage at the control pin of the integrated circuit chip is lower than a bias voltage of the integrated circuit chip, thus the integrated circuit chip is turned off, the relay is closed to activate the heating apparatus; the reverse resistance of the first diode reduces as the temperature of the data input device increases, thereby the voltage at the control pin of the integrated circuit chip increases; wherein upon the condition that the temperature of the data input device reaches the determined temperature, the voltage at the control pin of the integrated circuit chip exceeds the bias voltage to activate the integrated circuit chip, resulting in the power pin connected to the at least one I/O pins of the integrated circuit chip, which causes a part of current from the power supply to pass through the second resistor, thus reducing the amount of current through the relay, at which point the relay opens to shut off the heating apparatus.