BATTERY LEVEL MONITOR

             BATTERY LAVEL INDICATOR

 101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical ,

 This general- purpose 12V battery -level indicator  is build around the ubiquitous LED driver IC LM3914. It can check the  voltage level of any battery having output  voltage between 3V and 12V . 

The battery level is display in bar mode. When battery voltage is up to 12V ,LED1 through LED7 glow. similarly, when battery voltage is around 10.50V , LED1 through LED6 glow. A total of ten LEDs are used in this circuit . The battery under test power the  circuit .No addition power supply is required for this tester.

You can test up to 15V battery with this circuit  as it  has ten LEDs with  this circuit  as  it  has  ten  LEDs. The first nine LEDs 1 TO 9 will  glow  when  the battery  under test has 15V output .

 the  potential divider  comprising resistor R4 and R5 provides  reference input  signal  for IC2 at pin 5 . The visual indicator range depend  on the internal reference voltage of IC2 plus value of resistor R6 and preset VR1.With the components values used here the circuit  display between 3V(LED1) and 16.5V(LED10). 

In addition, a push-to read  arrangement  has been realised using popular timer IC LM555(IC1). IC1 is pressed momentarily of when the power is switched  on initially. Its output pin 3 goes high for about five seconds and transistor T1 conducts to provide positive supply at the common anode of LEDs.  This power supply is also ex tended to emitters of transistors T2 and T3 for activating the buzzer.  The LEDs up to the supply level of battery re main lit for the time duration of timer IC1 wired monostable multivibrator.  R2 and C2 determine the time period of the monostable multivibrator .
The circuit bunt around transistors and T3 sounds an alarm when the battery level goes low.  The audio alarm for the battery level can be decided by connecting the base of transistor T2 to a particular pin of IC2.  For example, if you want an alarm when the battery level goes to low 9V, connect the base of transistor T2 to pin 15 of IC2.  You will observe LED5 switching off and an alarm sounds.

Assemble the circuit on a  multi PCB and breadboard .  Before en closing the circuit in a box, calibrate the various voltage levels.  For calibration, connect the 15V variable regulated power supply and initially set it at 3V.  Press switch S1 and slowly adjust VR1 until LED1 lights up.  Similarly, increase the input voltage to 15V in steps of 1.5V.  Press switch S1 and slowly adjust VR1 until the corresponding LED (LED2 through LED9) lights up Re - check your calibration and when sure of its correctness, paint - lock preset VR1 and remove the variable power supply.  Now your battery - level monitor is ready for use!

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