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Battery Charging Light Circuit Answered

Dear All

I am building a small scale PV system and I want to implement a circuit that will allow a LED to light up when the battery is being charged from the PV cells

Currently I have a general purpose PNP transistor with a 2KOhm resistor for the base and a 1KOhm resistor in series with the LED, however when running this simulation the LED will not light, even when I lower the values of the resistors

Any help would be much appreciated 

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G4224T
G4224T

Reply 7 years ago

You probably haven't got enough voltage difference between the collector and base to switch the transistor on. The 1K resistor that goes across the supply rail will also be switched in parallel with your LED resistor too and would probably not provide enough current to light the LED.

Take the 1K resistor (the one at the rightmost of the circuit) out and add a 10K resistor from the junction of the transistor base / 2k resistor to ground to create a potential divider and it should work. Change the 1K LED resistor to a 680R resistor too to increase current.

I haven't tried it or calc'd it, its just a guess.

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EmptyCoffin92
EmptyCoffin92

Reply 7 years ago

Thanks ernestcraphead that worked perfectly :D