Patent ID: 8008604
Filing Date: 2011-08-30
Classification: F24C,F24H,H05B

Abstract:
1. A method of sensing an overheating condition in a portable electric heater having a heating element, a reference resistor having a known resistance of R_Reference, a plurality of thermistors organized into at least a first bank of multiple thermistors and a second bank of multiple thermistors and disposed proximate the heating element in substantially evenly spaced intervals, and a capacitor, the method comprising the steps of: placing the reference resistor in series with the capacitor to form a first RC timing circuit; determining an amount of time TIMER_Reference that it takes for a point between the reference resistor and the capacitor to reach a predetermined threshold voltage; switching, via a first control signal output from a microcontroller, only the first bank of multiple thermistors in series with the capacitor to form a second RC timing circuit; determining an amount of time TIMER_BANK# determining a resistance value R_BANK# performing a table lookup of a first temperature value corresponding to R_BANK# determining if the first temperature value is indicative of an overheating condition; switching, via a second control signal output from the microcontroller, only the second bank of multiple thermistors in series with the capacitor to form a third RC timing circuit; determining an amount of time TIMER_BANK# determining a resistance value R_BANK# performing a table lookup of a second temperature value corresponding to R_BANK# determining if the second temperature value is indicative of an overheating condition.