automatic light

GopherT

Joined Nov 23, 2012
8,009
On first guess, the transistor will only turn on when the DC charging voltage drops below the battery voltage.

It will likely turn on when there is a large draw from the battery and the capacitor is drained at each half cycle or if a connected battery has a voltage higher than the charger.

R2 is insuring the base voltage is pulled low to turn on the PNP transistor.

In the end, there is nothing to limit the base current at the transistor so I don't really like this circuit.
 

Thread Starter

aimaldaudkhan

Joined Jan 25, 2013
38
On first guess, the transistor will only turn on when the DC charging voltage drops below the battery voltage.

It will likely turn on when there is a large draw from the battery and the capacitor is drained at each half cycle or if a connected battery has a voltage higher than the charger.

R2 is insuring the base voltage is pulled low to turn on the PNP transistor.

In the end, there is nothing to limit the base current at the transistor so I don't really like this circuit.
why R2 is not working when main supply is on i use a simple wire instead of R2 it doesnot works but i take a resistor it starts work whats the main role of R2
 

BobTPH

Joined Jun 5, 2013
8,765
As already answered, the purpose of R2 is to turn on T1. If you replace it with a wire, you have shorted the power supply. Do you normally decide components are not needed and short them with a wire?

Bob
 

GopherT

Joined Nov 23, 2012
8,009
As already answered, the purpose of R2 is to turn on T1. If you replace it with a wire, you have shorted the power supply. Do you normally decide components are not needed and short them with a wire?

Bob
Thanks Bob ;),
I don't know what was missing in my explanation but, since he gave you the "thanks", my dribble didn't seem to do anything for the OP! HAHAHA!

This place is getting stranger and stranger!

GT
 
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