Published:2011/5/17 4:35:00 Author:Sharon | Keyword: Electric Blanket, Temperature Control | From:SeekIC
Electric blanket without temperature controller not only can hardly obtain a comfortable bed temperature, but also has huge energy consumption. What's worse, there may be fire hazard. Electric blanket with bimetallic thermostat although has improvements in energy-saving and security, but it's still difficult for it to adjust the temperature. Temperature control circuit with a PTC thermistor can overcome these shortcomings. 1. Principle circuit The electric blanket temperature control circuit is consistuted by the rectifier circuit and the temperature measurement and control circuit. Its principle is shown in Figure 2.11.1. Chart, RT1 and RT2 are the PTC thermistor for detecting the temperature of different regions, and also form a SCR VS trigger circuit together with the RP, C and VD6. RP also has the function of defaulting the constant temperature values. 2. Main components selectionPTC thermistor should be selected with Curie temperature 30 ℃, temperature resistance 5KΩ, and withstanding voltage 500V or more. VS should be chosen by the size of RL power. The circuit model selected here can meet the general use of electric blankets. C selects the best insulation performance polycarbonate film capacitors. 3. Installation and adjustmentThe recommended installation method is burying two PTC thermistors in the intensive sites of the electric wires. For example, the center of the feet and waist. In addition, the circuit is connected directly with the city electricity, and the PTC thermistor buried in the electric blanket and its terminations should have good insulation measures.
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