I have a circuit related issue. I intend to use S9013 instead of relay to switch 12V LED strip. I tried this circuit below and found out the brightness of the 12V LED is much lower comparing to directly hook up the 12V DC. I tried to replace the 10K resistor with 1K resistor and the LED seems brighter than the 10K resistor setting. The ESP8266 GPIO sends 3.3V signal. Should I hook up the GPIO directly to R1? How to calculate the suitable resistor of this circuit?
Is it safe to use transistor to switch 12v LED how to protect ESP8266 GPIO
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Re: Is it safe to use transistor to switch 12v LED how to protect ESP8266 GPIO
Max output current gpio is 12 mA
Let,s take 6 mA to be safe for our calculation
With 6 mA base/emitter current and transistor gain of 60 to 300 collector/emitter current could be 360 ... 1800 mA . Max c/e current of transistor is 500 mA
Output gpio 3.3 v voltage drop b/e 0.6 v = 2.7 v
Resistor value 2.7/0.006 = 450 ohms
So choice 390 ... 470 ohm for base resistor
Have a good day
Let,s take 6 mA to be safe for our calculation
With 6 mA base/emitter current and transistor gain of 60 to 300 collector/emitter current could be 360 ... 1800 mA . Max c/e current of transistor is 500 mA
Output gpio 3.3 v voltage drop b/e 0.6 v = 2.7 v
Resistor value 2.7/0.006 = 450 ohms
So choice 390 ... 470 ohm for base resistor
Have a good day
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