![]() We could use 10 MR resistors (It would be 0.0003 mA) if we were going to use low capacity batteries. 003 mA, especially for a battery with the characteristics we are using (4.5 Ah capacity), is a very good value. See, for example, if there were 4 resistors of 1KR, according to Ohm's Law, the loss would be: U = R * i => 12V = 4000R * i => i = 12V / 4000R => i = 3mA 3 mA constantly, but as we chose 4 resistors of 1 MR, we have: U = R * i => 12V = 4000000R * i => i = 12V / 4000R => i = 0.003 mA 0.003 mA of constant loss. What changes is the amount of current that would be lost in that system. Note that there could be 4 resistors of 5 KR, or 4 of 1 KR, or 4 of 330 R, or even 4 of 1 R, since, for the calculation of the voltage divider, the final result would be the same, calculate yourself. The value of the resistors was made according to the current drain, which naturally occurs in our load level measurement system. It is the time to explain the two points that remain unexplained, the first is why the resistors of 1 MR. This output voltage (V_OUT) will always be a fraction of the input voltage (V_IN) in relation to the values of resistors R1 and R2. The sensor itself, consists of a voltage divider, as seen in Figure 2, is a simple arrangement of two resistors and the ability to read the voltage between them. As there will be two batteries in series, the values we will use are 12 V, 4.5 Ah capacity, fluctuating from 13.5 to 13.8 V, in cyclic from 14.1 to 14.4 V, total.Īt the other end, we will use an Arduino analog port, which in the case of Arduino Uno, operate at a resolution of 10 bits and 5 V.įigure 2 - Scheme of a Voltage Divider and its formula There is some information that is crucial to build this circuit, the first is the properties of the battery in use, for example, for this experiment we will use two sealed 6 V lead acid batteries, 4.5 Ah capacity, in fluctuation from 6.75 to 6.90 V, in cyclic from 7.05 to 7.2 V, each. There is a simple way to measure this, so let's get to practice. ![]() So it is also called a sequential circuit.One of the main concerns of a project that will be powered by batteries is knowing exactly when they are about to discharge. This means that it will map input voltages. The Arduino Uno ADC is of 10-bit resolution (so the integer values from 0 - 210 1024 values). The IC contains adjustable reference voltage and an accurate 10-step voltage divider. Battery Voltage Indicator just read the value from Arduino Analog pin and convert it into a digital value by using the Analog to Digital Conversion (ADC) formula. So, the operating voltage of this LM3914 is 3V to 25V DC. The circuit will work even if the battery voltage goes down to 3V. The circuit is capable of monitoring about 10V to 15V DC supply. Here the preset is used for the calibration of the circuit. Here resistor R3 (56KΩ) and 10KΩ preset forms a potential divider circuit. This resistor usually controls the brightness level of the LEDs. Pins 6 and 7 are connected to the ground through a 18KΩ resistor. This mode is selected by the external switch 1 connected to pin no 9 of the IC. In this circuit, LEDs (D1-D10) are arranged in linear form to display the capacity of the battery level. Circuit Connection of Battery Level Indicator System We can extend this circuit to 100 steps by cascading LM3914 IC. In this circuit, each LED indicates a 10% battery level. This circuit is most suitable for indicating a 12V battery level. Now the circuit is ready to monitor higher and lower voltage ranges. Now disconnect the preset, measure the resistance across it and connect the resistor of the same value in place of R2. Connect a high-value variable resistor in place of resistor R2 and vary it until the D1 LED glows. Now remove the higher voltage from the input and connect the lower voltage to it. For that, we need to remove the resistor R2 and connect it with a higher voltage level and vary the preset until the D10 LED glows. Using some modifications, we can use this circuit to measure higher and lower voltage ranges also. Connect D1-D3 with a red LED which indicates shut down stage of your battery and use D4-D7 with blue colour LED which indicates the medium percentage of the battery and use green colour for D8-D10 to indicate maximum level achievement. ![]() We can also connect different colours of LEDs to indicate the actual status. For viewing the dot display, leave the 9th pin floating.For displaying bar graphs, connect pin no 9 to the supply voltage.It supports a wide range of temperatures from 0 to 70 degrees Celsius.No multiplexing interactions between outputs. ![]() LED driver outputs are current regulated.A programmable output current of 2mA to 30mA.The internal reference voltage of 1.2V to 12V.
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