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 NXP Semiconductors

  • Over Speed Warning device for Vehicle

  • Created: Jun 04, 2014

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Traffic accident is a tragic event that costs lives, and based on statistics, the second major cause of car accident is speeding. Speeding is still a human error, the faster you drive, the harder for you to maneuver and slower reaction time to prevent a road accident. This project is designed to alert the vehicle driver that a designated speed limit has been reached.

This device will be installed in the vehicle to monitor its Revolutions Per Minute (RPM) by the engine’s spark plugs. Testing and setting must be done to determine the maximum speed allowed. After the correct settings, the circuit is ready for implementation, which will indicate a warning signal when the speed limit is reached.

The circuit starts with the inductor coil acting as the sensor, the inductor will pick up the electromagnetic pulses generated by the engine’s spark plugs. The generated pulse will then be inputted to CA3140 op-amp operating as differential amplifier. The 74ABT04D hex inverter is used to further amplify the pulses and provides a clean pulse squaring. The clean squared pulse output will pass through a monostable multivibrator 74ABT04D IC used as a frequency discriminator. The same 74ABT04D IC along with the BC238 transistors and associate components are used to provide timings to the signaling side.

After the installation of the circuit, the setting of the designated speed limit will follow. The vehicle must be driven (in stationary) until it reaches the speed assigned, and then the trimmer resistor will be adjusted to turn the indicator (light and buzzer) ON. At this state, if the speed slows down, the indicator turns OFF.



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