Temperature controlled hand held hair dryer - has thermistor detecting temp. of reflected hot air to regulate heat output

摘要

The hand-held hair dryer has a casing which includes an air intake, an air outlet and a handle. A fan within the housing draws in air via the intake an expels it via the outlet, and a heating element heats the air before it is expelled. A return air passage near the outlet contains a thermistor which detects the temperature of air reflected from the hair during the drying process. The temperature of the thermistor controls the intensity of heat supplied by the element, and progressively reduces this intensity as the drying process continues, so that as the hair becomes dry, overheating is prevented. The control of the heating element is performed by a thyristor in accordance with the resistance of the thermistor.