I'm a computer programmer by trade who has taken an interest in Arduino with the hopes of eventually producing a particular hardware project that has captured my hobby/side-business interest.
I understand only a very little bit of electronics and am trying to fix that. Please be gentle if my questions are very basic or silly. I'm really trying to understand some new concepts.
I'm reading "Introduction to Electronics" 5th Edition by Earl D. Gates. I'm really enjoying it and finding that it lays out material in a structured and helpful way. It was well worth the $1.00 I paid on Amazon! ;-)
I'm reading through a section that deals with Ohm's Law and Kirchhoff's Current Law, and I'm struggling to understand some concepts.
I can understand (or at least do the calculations for) the
I = E / R equation. It's basic math, so that's not hard. The explanation of what figures in a circuit go where is also fairly easy to understand.
The book has drawn circuits with
? values for various parts of the circuit (voltage, current or resistance), and I am able to successfully solve for the missing values. Not too hard, actually.
What is currently confusing me is "voltage drop". I have a question that gives the following circuit:
The question asks, "How much voltage is dropped across resistor R2 in this circuit?"
So, first, we solve for current, which calculates to I = 4.5mA. (Actually, 4.485981308mA.)
Then, knowing that current is the same for the entire circuit, we can set up the following equation:
I2 = ER2 / R2 (which, why is it suddenly ER2, not just E?)
0.0045 = E / 3900
Therefore, voltage drop is 17.55V.
But what does this mean?
Using the same calculations, voltage drop for the different pieces of the circuit are:
Resistor 1: 0.0045 * 5600 = 25.20V
Resistor 2: 0.0045 * 3900 = 17.55V
Resistor 3: 0.0045 * 1200 = 5.40V
And those total to 48.15V, so our math is close but has minor rounding issues.
But, again, what does this mean?
Does it mean that tapping into the circuit between resistors 1 and 2 would give me 22.8V (48V - 25.2V)?
If I have a sensitive electronic component that accepts 3V-6V, would it be safe to draw this power from the circuit after resistor 3?
Am I even close to a proper understanding?
What I'm interested in is working with some 3.3V components, starting with with an input voltage that's maybe 3.7V (LiPo), maybe 5V (USB), maybe 9V, etc. I understand that my Arduino Uno already has power regulators that output 3.3V @ up to 50mA, but HOW does it do that?
It says it can accept 6-20V (but USB is 5V!), and somehow it deals with all of that excess voltage to provide a steady, regulated 3.3V. What dark magic is taking place here? ;-)
I realize that there are many, many components out there that will "just work" to give me the electrical output I desire (I've been playing with a few, like the LM317), but I'd like to really understand what's going on, not just know which component works. Thus far, all attempts to actually get the LM317 to work have failed, because I apparently have a serious lack of understanding on this issue.
Anyway, I really appreciate if you've read this far. Thanks for any help!