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To drive a 12v relay by atmega32 using BC547

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prathyks

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Hey everyone, i am not able to get a simple thing here.

I am trying to drive a relay by atmega32 using a BC 547 transistor.

my connections as of now are :

Relay Pin 1 (Coil) <------- +12v
Relay Pin 2 (Coil) ------> Collector (BC547)
From microcontroller -----> Base (BC547)(with 1k resistor in the middle)
Emitter (BC547) -----> Ground

further i have also connected a 10k resistor between base and emitter of a transistor..

But still relay is in always 'ON' state. Am not able to switch 'OFF' the transistor.

Thanks for the solutions.
 

prathyks, I recommend you to check the voltage at base... and then reply...
 

I don't see any problem with your connection so it must be your program
or you have done something previously to damage either the AVR pin or the transistor.

Disconnect the base resistor from the AVR, the 10K pull down will hold the transistor in off state,
then connect the !K input resistor to 12v, it should turn on.

You can either try with another pin or connected a led to the pin of the AVR
using a resistor about 330ohm for 5v,
then see if the led turns on/off.

Alex
 

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