The circuit is drawn for measurement of acceleration from –1000 mg until + 1000 mg. It can be placed in kantra’n the car and be supplied from the sheath of electric lighter. The circuit includes one indicative LED and a screen LCD.
The measurement of acceleration becomes with the use of IC from Analog Devices, the ADXL202. The particular element contains 2 autonomous vertical between them sensors, for the measurement in two axes. For the particular application becomes use of only it’s one. Acceleration meter measures dynamic or static acceleration from –2g until 2g (where g is the acceleration of gravity) and when this is equal to zero, exit is a signal PWM, with Duty Cycle 50%. As long as the acceleration increases, increases also the Duty Cycle, with biggest response the 75% (in the 2g), while for acceleration –2g, the Duty Cycle is 25%. As conclusion from more, has that for change 1g, is altered also the Duty Cycle of exit at 12,5%.
For more detail: LCD Car Accelerometer using microcontroller