Hi,
I am controlling a 5V relay using a microcontroller (NodeMCU) operating on 3.3V. So the GPIO pins will only provide 3.3V. Hence I have used a BC547 to control the relay. But I am confused if the BC547 transistor will be fully closed when i give 3.3V and deliver enough current to trigger the relay
I have attached the graph below that shows the collector current value for different base voltage. If my VBE is 3.3V then there is no collector current at ambient temperature. I think I am missing something here. Can some one pls help
thanks for answer gupta, but how can it be done? What value of resistor should i use? Also resistor is only used to control the current right?
Thanks for the answer i am slowy getting to understand this.
So the above graph is useless? I also did not find a graph for base current vs collector current.
So how much base current should i provide to base pin of bc547 if my collector current should be 70mA. Please help me with this. I also want to know formulae for calculating resistor value if my base voltage is 3.3V
All information given by the datasheet is useful from different aspects.
https://circuitdigest.com/article/npn-transistors
Follow the above link. I hope this will provide all answers of your quarries.
Sourav Gupta
PermalinkUse proper base resistor.
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Joined February 12, 2018 696Monday at 02:11 PM