HIGH_SPEED_WARNING

Published:2009/6/28 22:31:00 Author:May | From:SeekIC

Audible alarm tone generator drives waming Ioudspeaker to supplement 2-digit speed display that can be set to trip when vehicle speed exceeds 55-mph legal limit. Engine speed signal is taken from primary of spark coil. Switch in transmission activates circuit only when car is in high gear. All functions are performed by sections of LM2900 quad Norton opamp. A1 amplifies and regulates sparlocoil signal. A2 converts signal frequency to voltage proportional to engine speed. A3 compares speed voltage with reference voltage and turns on output transistor at set speed. A4 generates audible tone. Circuit components must be adjusted for number of cylinders, gear and axle ratios, tire size, etc. 10-μF capacitor connectea to A3 can be increased to prevent triggering of alarm when increasing speed mo-mentarily while passing another car.- Linear Applications, Vol. 2, National Semiconductor, Santa Clara, CA 1976, LB-33.



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