| 摘要 |
PURPOSE:To protect a machine from breakdown by providing a circuit for detecting the rotation speed of a fan motor and producing a signal when the rotation speed drops below a predetermined level. CONSTITUTION:When a fan motor 1 for radiating heat from the interior of an electronic machine is rotating steadily, output rotary waveform of the motor 1 is applied onto terminal A of a monostable multivibrator IC2 thus producing a low level voltage V0 from terminal Q. When the rotation speed of the motor 1 drops to a predetermined level, the IC2 detects the drop in the rotation speed of the motor 1 to produce a high level voltage V0 from the terminal Q. By such arrangement, the electronic machine can be protected from breakdown due to inner temperature rise. |
