Hi all,
I see this posting about selecting a resistor for a different circuit but it doesn't explain to me what I need for this particular implementation. http://forum.allaboutcircuits.com/showthread.php?t=43775
What I'm looking for is a way to tell what resistor I need for a Raspberry Pi GPIO (3.3v out, up to 50mA) to NP3904 base.
I've heard horror stories of hooking up circuitry to the Raspberry Pi and frying the board and I'm hoping someone here could help before I get to that point.
I've selected an NP3904 (due to it being the only one available at RadioShack which would saturate at 3v). I currently have the base connected directly to the Raspberry Pi GPIO pin, the Collector to my load (12v), and the Emitter to common ground.
It works as-is, but I'm worried about tidying everything up and reattaching to the wall if I'm going to need to replace this when it burns up in the future. Here is the NP3904 datasheet http://www.fairchildsemi.com/ds/2N/2N3904.pdf
What am I looking for in order on that datasheet to figure out which resister I need in between the Raspberry Pi's GPIO and the base of the NPN?
Is there a way for me to figure this out on my own in the future?
Thank you for your time, I'd appreciate any help!
I see this posting about selecting a resistor for a different circuit but it doesn't explain to me what I need for this particular implementation. http://forum.allaboutcircuits.com/showthread.php?t=43775
What I'm looking for is a way to tell what resistor I need for a Raspberry Pi GPIO (3.3v out, up to 50mA) to NP3904 base.
I've heard horror stories of hooking up circuitry to the Raspberry Pi and frying the board and I'm hoping someone here could help before I get to that point.
I've selected an NP3904 (due to it being the only one available at RadioShack which would saturate at 3v). I currently have the base connected directly to the Raspberry Pi GPIO pin, the Collector to my load (12v), and the Emitter to common ground.
It works as-is, but I'm worried about tidying everything up and reattaching to the wall if I'm going to need to replace this when it burns up in the future. Here is the NP3904 datasheet http://www.fairchildsemi.com/ds/2N/2N3904.pdf
What am I looking for in order on that datasheet to figure out which resister I need in between the Raspberry Pi's GPIO and the base of the NPN?
Is there a way for me to figure this out on my own in the future?
Thank you for your time, I'd appreciate any help!