There are certain usage patterns that you will find all over the place, e.g.:
- Current-limiting resistors
- The resistor divider (two resistors between e.g. 3.3V and GND. The point between the two resistors will be between 3.3V and 0V, depending on the resistor values. Sometimes you need a certain voltage. For example to bias transistors.
- Delays, using a resistor and a capacitor. The values will determine the delay.
- Capacitors next to oscillators
- Filters, using a resistor and a capacitor. The order and the values will determine the cutoff frequency.
- Most capacitors on a PCB probably sit right next to a chip. Often, at least one per chip. They get rid of noise already on the line, and act as short-term energy storage for the chip next to it.
- Decoupling capacitors to get rid of the DC component of a signal (i.e. if there is a signal fluctuating between 4.5V and 5.5V before the cap, it'll be -0.5V and 0.5V behind the cap. Often, you need to add a DC component and later remove it, so that's two capacitors already.
Obvious but it never occurred to me that experienced person sees far fewer parts than layman when looking at the board, for expert its like yeah "file read there", "serialization here" (if I were to use programming analogy) but layman sees gazillion little parts magically working together.
They were quoting "The Matrix". But you're probably correct, even in the movies the existence of "The One" was a pretty serious security bug, and the entire need for "agents" was a workaround for other bugs.
"if there is a signal fluctuating between 4.5V and 5.5V before the cap, it'll be -0.5V and 0.5V behind the cap" if there's a resistance to ground after the capacitor. I've accidentally planned an audio amp with input decoupling capacitors, didn't add ground resistors before the capacitors, so if you plug it into an audio output with DC-blocking capacitors but not resistors to ground, the voltage in the middle could be anything.
Also worth mentioning are pull-up or pull-down resistors. They give a pin a default state when nothing is driving the pin. You will often see them on reset pins and on inputs from buttons.
- Current-limiting resistors
- The resistor divider (two resistors between e.g. 3.3V and GND. The point between the two resistors will be between 3.3V and 0V, depending on the resistor values. Sometimes you need a certain voltage. For example to bias transistors.
- Delays, using a resistor and a capacitor. The values will determine the delay.
- Capacitors next to oscillators
- Filters, using a resistor and a capacitor. The order and the values will determine the cutoff frequency.
- Most capacitors on a PCB probably sit right next to a chip. Often, at least one per chip. They get rid of noise already on the line, and act as short-term energy storage for the chip next to it.
- Decoupling capacitors to get rid of the DC component of a signal (i.e. if there is a signal fluctuating between 4.5V and 5.5V before the cap, it'll be -0.5V and 0.5V behind the cap. Often, you need to add a DC component and later remove it, so that's two capacitors already.