I am using this directory to store code for the Raspberry Pi 3B+ that I own wherein I take the GPIO kit and some goodies I bought on Amazon and screw around with circuits.

The maximum recommended draw from one of the 3.3V pins is 50 mA or 0.005 A.

Since

V / I = R

So..

3.3V / 0.005A = xΩ

Therefore we need at least a resistance of...

660Ω

My tests utilized resistors with 1kΩ or 1000Ω, which kept the Raspberry Pi safe. Here is the link to the kit I used. Pretty cheap @ <$15! Before using/buying this kit, you can see all of the data sheets on what is inside of the kit by downloading the zip file for this kit from the vendor's website.

Also watched a neat youtube video giving a high level overview of different components found in most circuits. This is a summary of the notes I took from that video.

Voltage, Current, Resistance Circuit - Closed loop that carries electricity. Current (electric) - The flow of electrons in a circuit. (Negative to positive) Hole Current - Positive directed current. (a.k.a. “I”)

Current is in ampere (A) or “I” = charges through a current, coolants per second

Voltage (V) or “V” = Push that causes the current to flow

Resistance (Ω) or “R” - Opposes the current flowing through a circuit

OHM’s LAW —————— V = I * R

DC / AC Direct Current = Constant Current Flow, direct and constant voltage (battery) Alternating Current = Current moves back and forth (wall socket)

Hz is the rate at which power frequency is going back and forth. Default is 60Hz (60 times per second)

Open Circuit - Lightswitch OFF, no flow Short Circuit - least resistance path that skips the functionality of the circuit and simply generates heat without resistance

Battery / Power Source Volts V

——(+ -)—— 

Resistor Ohms Ω

——v^v^v^v———

Capacitor Electric field

——-| |———

Inductor Magnetic Field

——-mmmmm——

Dioide One way circuit

——>|——-

LED Light emitting diode

——>^|——

Transistor Switch // amplifier

    /
——-<|
    \

Transformer Upgrade/downgrade voltage

——\    /——
   3||E
——/    \——

Follow at your own risk. No Guarantees that anything here works. Always remember to stay safe and have fun!