project report on battery level indicator pdf

[jaseela123d]

Normally in mobile phones the battery level is shown as a point or bar. This allows you to easily recognize the battery level. Here we present a battery level indicator circuit that allows you to know the battery level of a device based on the amount of LEDs that are shining. It uses ten LEDs in total. Then if three LEDs shine, it indicates a battery capacity of 30 percent.

Unlike mobile phones, in which the function of the battery level indicator is integrated with other functions, here only a comparison IC (LM3914) does it all. The LM3914 uses ten comparators, which are assembled internally in the voltage divider network according to the current division rule. Therefore, divide the battery level into ten parts.

Battery level indicator circuit

The circuit derives the power supply for its operation from the device's battery. It uses ten LEDs connected in a 10-point mode. The use of different colored LEDs makes it easier to recognize the voltage level depending on the calibration performed. The red LEDs (LED1 to LED3) indicate a battery capacity of less than 40 percent.

Orange LEDs (LED4 to LED6) indicate a battery capacity of 40 to less than 70% and green LEDs (LED7 to LED10) indicate a battery capacity of 70 to less than 100%. The brightness of the LEDs can be adjusted by varying the value of the preset VR2 between pins 6 and 7.

Diode D1 prevents the circuit from connecting the battery with reverse polarity. The tenth LED lights up only when the capacity of the battery is full, ie the battery is fully charged. When the battery is fully charged, the relay controller transistor T1 leads to energize the relay RL1. This stops charging through normally open contacts (N / O) of relay RL1.

For calibration, connect the regulated and variable 15V power supply and set it initially to 3V. Slowly adjust VR1 until LED1 lights up. Now, increase the input voltage to 15V in steps of 1.

2 V until the corresponding LED lights up (LED2 to LED10).

Now the circuit is ready to show any voltage value with respect to the maximum voltage. Since the number of LEDs is ten, we can easily consider an LED for 10 percent of the maximum voltage.