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- Using NPN transistor as switch 3 answers
I have a NPN transistor (2N3904), I would like to be able to turn on my LED panel - 37v (don't know the amps) with my Arduino Uno, which gives output of 5v, 0.2 amps.
As far as I understood, the Arduino will be connected to the base of the NPN transistor. if I put a diode or a resistor between the Arduino and the NPN transistor's base, following the tutorials it "should" work, but I don't want to burn my Arduino down.
I don't understand, if the transistor is a 'switch', when I give electricity to the base, why is there electricity coming into the base from the collector? shouldn't it go straight to the emitter? how can I know how big of a resistance to put, between the Arduino and the base of the transistor? In addition, should do 'GRD' from Arduino go to the LED's negative terminal? Thanks