Im a first year engineering student and i think i am misunderstanding something very basic here.
I simplified the circuit to just one led and resistor to wrap my brain around it better
my issue is this
I am getting ~4.7v from 5v to the NPN collector
so in theory the rest of my circuit see a voltage source of 4.7 , you know Thevenin and all.
so with a 220 ohm resistor i should expect a current of ~20mA or so… but i am reading 9mA .
and i do not understand why… is my led like a resistor too?
Voltage drop of the led reads 2.9
that leaves the resistor with about a 2.0v drop.
so i dont understand how my led will ever “see” 5v and 20mA
and voltage drop across one single resistor and a voltage source… how do you measure the voltage drop of a resistor is in essence what your measuring is the voltage source?
I know my theory is all messed. First year engineering student i just finished my DC class going into AC in the summer. I mean i learned a lot because it all made sense in class and measuring this and that but just resistors with other resistors, the led is throwing my expected values off, rather i am not sure how to satisfy the led to get it 5v from 5v voltage source and at the same time limit the current it sees to 20mA if after my resistor the led no longer sees 5v
schematic in the attachment below