Component Field Guide

Power source

Supplies the voltage that drives current around the loop, out of the + terminal and back into −.

Symbol: the long line is +, the short line is −.
In real life: our power supply — red wire = +, black wire = −, supplying 5 V. (Inside it: a rechargeable battery.)
Unit: volts (V).
Watch out: red touching black with nothing in between is a short circuit — safety rule 1.

Wire, pinch & jumper

The connections. Any solid line in a schematic; everything a line touches is one node.

Symbol: a plain line. A dot where lines meet = joined there; no dot = just crossing.
In real life: a finger pinch (lesson 1!), a jumper wire, or a breadboard row's hidden metal strip.
Resistance: ≈ 0 Ω — current flows through for free.
Watch out: in a pinch, metal must press metal (skin can't conduct for you) — and a jumper can be broken inside its plastic. Beep-test when in doubt.

Resistor

The current limiter. Adds a known amount of resistance to the loop, which sets how much current flows — and protects components that would otherwise draw more than they can survive.

Direction: either way — no polarity. The most forgiving part in the kit.
Unit: ohms (Ω). 1 kΩ = 1,000 Ω. Bigger number = harder squeeze = less current.
In real life: a little tan cylinder with colored stripes — the stripes are its value (chart below).
Bonus fact: the energy it absorbs becomes heat. A resistor asked to absorb too much gets hot.

The resistor color code: first stripe = a digit, second stripe = a digit, third stripe = how many zeros to hang on the end. Most resistors add a gold stripe (±5% tolerance) — gold marks the end, so start reading from the other side.

Color	Digit
black	0
brown	1
red	2
orange	3
yellow	4
green	5
blue	6
violet	7
gray	8
white	9

Kit value	Stripes
220 Ω	red·red·brown
470 Ω	yellow·violet·brown
1 kΩ	brown·black·red
4.7 kΩ	yellow·violet·red
10 kΩ	brown·black·orange

Not sure? The multimeter's Ω mode settles every argument — part out of the circuit, fingers off the metal.

LED light-emitting diode

Turns current into light — but only in one direction. The triangle points the way the current flows.

Direction: one-way street. Long leg = + side (toward the supply's +). Legs trimmed? The flat spot on the dome's rim marks the − side.
Voltage drop: red/yellow/green ≈ 2 V · blue/white ≈ 3 V — the datasheet name is forward voltage. In series, drops add.
Backwards? Nothing happens — it just blocks. Flip it.
Watch out: never power an LED without its resistor bodyguard — a naked LED can pop. Safety rule 2.

Slide switch

A drawbridge for the loop: open = broken loop, closed = complete loop. It works anywhere in a series path.

Symbol: a lever and a gap — only two terminals, because a schematic cares about one thing: is the loop open or closed? Your real part has three legs; the symbol doesn't draw the one you leave empty.
Legs: three. The middle leg is the common one — it connects to one end leg or the other, depending on the slider. Use the middle plus either end.
Direction: either way around.
Watch out: wiring the two outer legs skips the middle — that "switch" never conducts in either position. Classic head-scratcher.

Arriving later this semester

Potentiometer lesson 5

A resistor with a knob: the arrow is a slider ("wiper") that taps any point along the resistance.

Also called: a variable resistor — or just "a pot." Same part, all three names.
Legs: three. The outer two are the ends of a fixed resistor; the middle is the wiper.
Value: ours are 10 kΩ — measured outer leg to outer leg, and that never changes. The knob doesn't change the pot's size; it changes where the split falls inside it.
The trick: it's an adjustable voltage divider — turn the knob, move the split.
In real life: every volume knob you have ever turned.

Capacitor lesson 6

A bucket for charge — fills up, then empties, and takes time to do either. Time is what we'll use it for.

Unit: farads — but a whole farad is enormous, so ours are marked in microfarads (µF) and nanofarads (nF). 1 µF = 1,000 nF.
Ceramic (small discs): either way around.
Electrolytic (little cans): polarized! The striped side is −, the long leg is +.
Reading the value: cans print it outright (1000 µF). Discs use a three-digit code instead: 104 means 10 with four zeros, in picofarads — 100,000 pF, which is 100 nF.
Watch out: an electrolytic wired backwards heats up and can burst its can. Stripe to −, always.

Transistor lesson 7 · NPN

The electric lever: a trickle of current into the base (B) lets a flood flow from collector (C) to emitter (E).

Legs: three — base, collector, emitter. The symbol's arrow sits on the emitter.
In real life: a little black half-cylinder with three legs and a flat face.
Check first: which leg is which varies between part numbers — always check the lesson's diagram for your part before wiring.
Watch out: the base behaves like a small LED — it opens at ≈ 0.7 V and drops that much no matter what. So the base never connects straight to 5 V: it always gets its own resistor, exactly like safety rule 2. A bare base across the supply is a cooked transistor.

LDR lesson 8 · light-dependent resistor

A resistor that changes its mind: bright light = low resistance, darkness = high resistance.

Also called: a photoresistor — same part, both names are everywhere.
Direction: either way.
Try it: put your meter on Ω and cover it with your hand — watch the number climb.
The payoff: team it with a divider and a transistor and you've built a night-light.

555 timer lesson 9 · your first chip

A whole circuit sealed in a black box: it makes steady on-off pulses — blinks you can see, and later, tones you can hear.

Legs: eight. The notch or dot marks pin 1; count counterclockwise from there (viewed from the top).
On the board: it straddles the ravine, one row of legs per side.
Watch out: a chip plugged in backwards gets hot fast. Notch first, power after.

Piezo / speaker lesson 10

Turns the 555's pulses into sound — the same on-off signal as the blinker, just fast enough that your ear hears a tone where your eye saw a flash.

Direction: either way around.
In real life: the piezo is a brass disc about the size of a coin; the speaker is a miniature version of the cone in your headphones.
Watch out: a speaker's coil is nearly a short circuit — a few ohms — so it gets a resistor in series, the LED's bodyguard idea all over again. A piezo sips current and needs no such help.

In your kit now