Battery Indicator Using Zener Diode

[gauravkothari23]

Hi all.
I need to make a battery indicator where a LED glows when the voltage is below 3.6V. i have attached a circuit diagram of battery indicator using 3.6V zener diode and PNP transistor. can anybody please let me know if the things would work or need to change something.

 

[KlausST]

Hi,

The circuit seems to be from a simulation tool. Does it work in simulation?

Can you describe the function principle?

Is it really a good idea to switch ON a LED when charge is low? This may lead to extensive draining out the battery ... and most probably this will kill the battery.

Klaus

 

[gauravkothari23]

Hi,

The circuit seems to be from a simulation tool. Does it work in simulation?

Can you describe the function principle?

Is it really a good idea to switch ON a LED when charge is low? This may lead to extensive draining out the battery ... and most probably this will kill the battery.

Klaus

i am using a 1.5V x 4 alkaline battery for my project. the basic principal is when the voltage is above 3.6V the current would flow through the zener diode and will keep the PNP transistor base high which would keep the led OFF. and when the voltage reaches below the 3.6v the diode would resist the flow of current which would make the transistor base pin low with the help of R15 resistor, which is pulled down to GND, which will make the LED glow. but while stimulation the LED does not go OFF at any voltage. i tried it from 12V to 2V. but the LED stays ON.
yes it will kill the battery when the system is on and voltage is above 3.6V, so what changes can i make to let the battery drainage to be nominal

 

[KlausST]

Hi,

basic principle of a BJT:
If there is no base current ... then there willl be no collector current.

Similar: if base-emitter voltage is low, then LED is OFF.

There is something wrong with your idea.

Klaus