Battery Status Indicator with LED Circuit Schematic Diagram

Operate with 5 to 12 volt, this circuit can be useful to mainly monitor the capacity of the batteries, portable and easy to operate. LED D1 flashes to attire the user’s attention, signaling that the circuit are running. The circuit generate about two LED flashes per second with current consumption about 200uA. The sequence of LED flashes are generated with transistor Q1 and Q2 that wired as an uncommon complementary astable multivibrator. Both are off 99% of the time, saturating only when the LED illuminates, thus contributing to keep very low current consumption.


R1,R7—————————————–220R 1/4W resistors

R2———————————————120K 1/4W resistor

R3———————————————5K6 1/4W resistor

R4———————————————5K 1/2W trimmer cermet

R5———————————————33K 1/4W resistor

R6———————————————680K 1/4W resistor

R8———————————————100K 1/4W resistor

R9———————————————180R 1/4W resistor

C1,C2—————————————–4u7 25V electrolytic capacitors

D1———————————————BAT46 100V 150mA schottky-barrier diode

D2———————————————LED 5mm

Q1———————————————BC547 45V 100mA NPN transistor

Q2———————————————BC557 45V 100mA PNP transistor

B1———————————————5 to 12 V battery

This circuit will work with battery supply voltages in 5-12V range. When the battery voltage approaches the exhausting value, the LED flashing frequency will fall suddenly alert the users, and when the battery voltage fallen, the LED will remain permanently off. Range and the LED flashing can be stopped at the desired battery voltage by adjusting trimmer R4. This can be modified by changing R3 and R4 value slightly. The current consumption of the circuit can be reduced further on by rising R1, R7 and R9 values.

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