Automatic heater controller
OwnerRonald S. Scharlackinventor
Life of this patent
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Abstract
A system for controlling the temperature of the heater element of a heating apparatus by controlling the resistance of the heater element. In a preferred embodiment, the control system monitors a sensing excitation voltage at the heater element for comparison with a reference voltage, preferably at or near the zero-crossings of the heater power source cycle, and thereupon operates so that power to the heater element is always applied and terminated at zero-crossings of power cycle. In a preferred embodiment, the controller is arranged to permit only integral cycles of power to be applied to the heater element to avoid a DC bias buildup and undesirable loading of the power line.
Claims28
A system for controlling the temperature of a heater apparatus having a heater element therein, the electrical resistance of said heater element determining the temperature of said apparatus, said system comprising
- means for providing a heater voltage for said heater element;
- means responsive to said heater voltage for detecting zero crossings thereof;
- means responsive to said zero crossing detecting means for providing sensing excitation voltage at or near said zero crossings;
- circuit means including said heater element and responsive to said sensing excitation voltage for sensing the excitation voltage at said heater element and for providing a reference voltage;
- means for comparing said excitation voltage at said heater element and said reference voltage for producing an output representing the polarity of the difference therebetween;
- and
- control means responsive to said zero-crossing detecting means and to the output from said comparing means for controlling the application of said heater voltage to said heater element at or near said zero crossings.
Dependencies are inferred from the claim text.