Battery level indicator indicates the status of the battery just by glowing LEDs. For example six LED’s are glowing means battery capacity 60% remains. This article gives you an overview of how to design a battery level indicator. You can use this circuit to check car battery or inverter. So by using this circuit, we can increase the lifetime of the battery.
Battery Level Indicator Circuit Principle:
The heart of this battery level indicator circuit is LM3914 IC. This IC takes input analog voltage and drives 10 LED’s linearly according to the input analog voltage. In this circuit, there is no need of resistors in series with LEDs because the current is regulated by the IC
Circuit Components:
- Lm3914 IC
- LED’s -10
- SPST switch
- Resistors -18k,4.7k, 56k
- Potentiometer – 10k
- 12V battery
- Connecting wires
Battery Charge Indicator Circuit Design:
In this circuit LED’s (D1-D10) displays the capacity of the battery in either dot mode or display mode. This mode is selected by the external switch sw1 which is connected to the 9th pin of IC. 6th and 7th pins of IC are connected to the ground through a resistor. This resistor controls the brightness of LEDs. Here resistor R3 and POT RV1 forms potential divider circuit. Here pot RV1 is used for calibration. There is no needforf any external power supply to this circuit.
The circuit is designed to monitor 10V to 15V DC. The circuit will work even if the battery voltage is 3V. The operating voltage of this IC is 3v to 25v DC. Lm3914 drives led’s, LCDs and vacuum fluorescents. The IC contains adjustable reference and accurate 10-steps divider. This IC can also acts as a sequencer.
Lm3914 Features:
- Internal voltage reference from 1.2 to 12v DC.
- Programmable output current 2mA to 30mA.
- LED driver outputs are current regulated.
- No multiplexing interaction between outputs.
- It supports wide range of temperature from 0 to 70 degree Celsius.
- For bar graph display – connect 9th pin of IC to the supply
- For dot display – leave the 9th pin of IC
We can also connect different color led’s to indicate the status. Connect D1 to D3 red LED’s which indicates shut down stage of your battery and use D8-D10 green color LED’s which indicates 80 to 100 percentage of the battery and use yellow color for remaining.
Good one
Thank you for your feedback.
Could you please tell me, how did you choose the particular values of resistors? Anyway(Formula) to calculate the values of the Resistors?
the author only can explain how he calculated resistor here but i can give you a basic idea.
Ohm’s law is the RAMAYANAM for the circuit designer and V=I*R is the center principle of design the value of resistance. first you take the datasheet of particular ic or transistor and look for the current and voltage rating to be present in the particular port or leg and then apply ohms law then you can find the resistance value. for example if you take data sheet of BC 547 you can find 3 tems written their
1) Base voltage & current
2) collector current
3) gain of transistor (hFE value )
see how much current and voltage you require at base of transistor then subtract it from the potential of circuit and divide it with the particular voltage with current you required then the value you got will be the resistance in Ohms. multiply the base resistance value with current gain of transistor and the answer will be collector resistance. this is the way of designing the resistor designing in a circuit. if the designed resistance is higher than the required value, the component will not get sufficient current and result energy loss and the circuit efficiency will be low . hFe value (current gain ) can be find out via multi meter too.
then put it in the equation P=(v*v) /R and you will get how much power of the resistance to be connected