Patent ID: 7293914

Claim:
A temperature detecting heater with an indicating structure for an aquarium, said temperature detecting heater has an electric power line extending through a top housing into a glass tube, said power line is connected with a printed circuit board to supply electric power; said printed circuit board is connected with a mica plate provided with a heating element, said printed circuit board and said heating element are sealed after assembling of said top housing with said glass tube; and an indicating structure is provided on said temperature detecting heater, said indicating structure includes a control circuit and a two-color LED indicating lamp, after said temperature detecting heater is turned on, a plurality of temperature detectors of said control circuit detecting a voltage generated and corresponding to a detected temperature of water to compare the detected temperature with a reference voltage generated in corresponding to a preset temperature at a set point; when said detected temperature at a detected point is lower than that of said set point, a heating element of said temperature detecting heater is controlled to work normally and makes said LED indicating lamp emits light with a first color; when said detected temperature at said detected point is higher than that of said set point, said heating element is controlled to stop working and makes said LED indicating lamp emits light with a second color, wherein amount of said temperature detectors in said control circuit is two, one of said temperature detectors is one used in dry electric heating for protecting a circuit during heating, while the other one is a water temperature detector to avoid overly high temperature of water, wherein said control circuit has a first comparator to compare a voltage generated in corresponding to a detected temperature of water with a voltage generated in corresponding to a preset temperature, and a second comparator to compare a voltage generated in corresponding to a detected temperature in electric heating with a voltage generated in corresponding to another preset temperature; said first comparator and said second comparator output signals to an OR gate; a third comparator compares an output signal of said OR gate with a signal at a negative input terminal of said third comparator; a coupling capacitor CAP is used to receive an output signal of said third comparator to couple with an alternating signal to activate a triac, said triac controls heating of said heating element when said triac is triggered, and said two-color LED indicating lamp emits light of said first color; and said heating element does not emit heat when said triac is not triggered, and said LED indicating lamp emits light of said second color.