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  • Car Battery Level Monitor

  • Created: Jul 27, 2015

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The battery plays a big role on the startup process of any car automotive system. It supplies the necessary current to start the engine. After starting the engine, the alternator begins to generate power and becomes the main source of electrical power to all electrical components within the car. When the current supplied by the alternator is not enough, the battery acts as an electrical reservoir and supplies the additional current required. Usually, failure in battery monitoring and maintenance causes problem to the start-up process of a car and in some other electrical components. That is why the goal of this reference design is to provide a simple circuit to display the battery level using a S912XHY128F0CLM microcontroller, a passive network sensor and an LCD display.

The operation of this circuit can be simplified into three stages: reading battery voltage level, conversion, display battery level. The microcontroller, using its analog pin (AN00), reads the battery voltage level through the passive network composed of R1, R2 and C13. The diode MBRS120 serves as a reverse polarity protection to prevent damage to the microcontroller in case of reverse polarity connection. The resistors (R1 and R2) act as a voltage divider network stepping down the voltage coming from the battery for over-voltage protection and at the same time to equalize the maximum voltage of the battery to the reference voltage of the Analog-To-Digital (ATD) converter module of the microcontroller. The analog value read by the microcontroller will be converted into digital value. Based on that value, the microcontroller will display the battery level to the LCD screen. In order to accurately display the battery level, the ATD of the microcontroller must be calibrated with respect to the passive network sensor. The calibration process is done through software programming of the microcontroller.

The S912XHY128F0CLM microcontroller ATD converter module has 12 channel multiplexed analog inputs. Its ATD converter module can convert a single reading as fast as 3 microseconds. The ATD converter module high resolution feature (8/10 bit resolution) enables the S912XHY128F0CLM microcontroller to deliver a much more accurate display of the battery level used in a car automotive system.