Abstract: A temperature control circuit which is capable of operating a microprocessor on a very low voltage source. The temperature control circuit uses a pair of field effect transistors and a zener diode in an oscillator circuit to amplify the source voltage. A microprocessor is supplied by the amplified source voltage, and is connected through a transistor to a temperature sensing portion of the circuit. The microprocessor uses the transistor to turn the power to the temperature sensing circuit portion off between temperature samples. By turning the temperature sensing circuit power off between samples, the average power drain by the control circuit is an amount that can be met by the amplified voltage from the low voltage source.

Abstract: An oil fryer control system simultaneously controlling oil temperature and cooking time. A proportional, integral and derivative temperature control is used to maintain the oil temperature below and above a predetermined set point temperature. In addition, a cooking time control varies the cooking time within a predetermined range of temperature error as a function of a stored time-temperature relationship. The invention provides the capability of cooking different products having different cooking parameters in the same or different oil vats.