🍞 Show realistic breadboard layout (Fritzing-style)
Power module 5V → red (+) rail → resistor → LED long leg (+); LED short leg (−) → green jumper → blue (−) GND rail. Swap the resistor value and watch the brightness change.
Reading Resistor Color Codes
Resistor
Color Bands (Band 1 · Band 2 · Band 3)
How to remember
100Ω
Brown ·
Black ·
Brown
1 · 0 · ×10 = 100
220Ω
Red ·
Red ·
Brown
2 · 2 · ×10 = 220
1kΩ
Brown ·
Black ·
Red
1 · 0 · ×100 = 1,000
10kΩ
Brown ·
Black ·
Orange
1 · 0 · ×1,000 = 10,000
Steps
1Set your power supply module to 5V. Connect the + and − rails on your breadboard.
2Insert the LED: long leg (+) in one row, short leg (−) a row away.
3Connect 5V → 100Ω resistor → LED (+) → LED (−) → GND. Notice the brightness.
4Swap in 220Ω, 1kΩ, 10kΩ one at a time. Record what you see in the table above.
🔬 The Science: Ohm's Law
V = I × R — Voltage = Current × Resistance. Higher resistance means less current flows, so the LED gets dimmer. The resistor is a "gatekeeper" that controls how many electrons get through per second.
🤔 Think About It
What happens if you remove the resistor completely? (Try it for just 2 seconds — feel the LED. Why do you think it gets warm so quickly?)
3
Dimmer Knob Light
★★★ELEGOO Kit
🎯 Use a potentiometer (a twistable resistor) to smoothly control LED brightness — just like a real dimmer switch.
🍞 Show realistic breadboard layout (Fritzing-style)
Pot: right leg → 5V (red), left leg → GND (green). The middle "wiper" leg → 220Ω → LED (+); LED (−) → GND rail. Turning the knob changes the wiper voltage, so the LED dims and brightens.
Potentiometer Pin Guide
A potentiometer has 3 legs. Looking at the flat front of the knob:
• Left pin → connect to GND
• Middle pin (wiper) → this is the output that goes to the 220Ω resistor
• Right pin → connect to 5V
Turning the knob moves an internal slider between the left and right pins.
Steps
1Set power supply to 5V. Insert the potentiometer into the breadboard (it has 3 pins, all in a row).
2Wire: Left pin → GND, Right pin → 5V.
3Wire from Middle pin (wiper) → 220Ω resistor → LED (+) → LED (−) → GND.
4Slowly turn the knob from one end to the other. The LED should smoothly brighten and dim!
🔬 The Science: Variable Resistance
A potentiometer is a resistor with a sliding contact inside. Turning the knob changes how much of the resistor's length is in the circuit — from nearly 0Ω all the way to 10,000Ω. More resistance = less current = dimmer LED.
🤔 Think About It
Why do we still need the 220Ω resistor even though the potentiometer is there? What would happen if the potentiometer was turned all the way to 0Ω with no safety resistor?
⭐ Bonus
Put a small piece of tape on the potentiometer shaft and mark "brightest" and "just barely on" positions. How many degrees apart are they?
4
Capacitor Fade-Out Switch
★★★ELEGOO Kit
🎯 Press a button to light the LED — then watch it slowly fade out on its own, like a hallway light that delays before switching off.
🪣A capacitor is like a tiny rechargeable bucket. When you press the button, it fills with charge in a split second. When you release the button, it slowly drains — and that draining current keeps the LED glowing!
⚠️ IMPORTANT: Electrolytic capacitors have polarity!
The leg marked with a "−" stripe (or shorter leg) must go to GND. Putting it in backwards can damage the capacitor.
Circuit Diagram
🍞 Show realistic breadboard layout (Fritzing-style)
5V → button → Node A. From Node A two parallel branches: (1) capacitor + leg → GND (the bucket that drains slowly), and (2) 1kΩ → LED (+) → GND. Release the button and the draining capacitor keeps the LED glowing. Watch capacitor polarity: + leg to Node A, striped (−) leg to GND.
Steps
1Insert the capacitor: longer leg (+) into Node A row, shorter leg (−) to GND.
2Wire: 5V → button → Node A → 1kΩ resistor → LED (+) → LED (−) → GND.
3Also connect Node A → capacitor (+) → capacitor (−) → GND (this branch is in parallel with the LED+resistor).
4Press the button: LED lights up instantly as capacitor charges.
5Release: LED slowly fades over 1–3 seconds as capacitor drains. ✨
🔬 The Science: RC Time Constant
Fade time ≈ R × C. With a 1kΩ resistor and 470µF capacitor: 1,000 × 0.000470 = 0.47 seconds. Use a bigger capacitor → longer fade. This "RC time constant" is used in real camera flash circuits, car courtesy lights, and more!
⭐ Bonus Challenge
If your kit has a larger capacitor (e.g. 1000µF), swap it in. Does the LED stay on longer? Time it with a stopwatch and record the difference!
5
Auto Night Light
★★★★ELEGOO Kit
🎯 Build a sensor circuit that automatically turns on an LED when it gets dark — no button needed, ever.
A special resistor that changes based on light: Bright light → low resistance (current flows easily) Darkness → high resistance (current barely flows)
🔌 PN2222 Transistor
An electronic switch with 3 legs: Base, Collector, Emitter. When enough current enters the Base, the switch "opens" and current flows from Collector to Emitter.
PN2222 Pin Layout (Flat Face Toward You)
Circuit Diagram
🍞 Show realistic breadboard layout (Fritzing-style)
Left = light-sensor divider: 5V → 10kΩ → Node A → LDR → GND. Orange wire taps Node A into the transistor Base (B). Right = LED branch: 5V → 1kΩ → LED (+) → LED (−) → Collector (C); Emitter (E) → GND. In the dark the LDR's resistance rises, Node A voltage climbs, the transistor switches on, and the LED lights.
Steps
1Set power supply to 5V. Insert the PN2222 transistor into the breadboard (3 legs in separate rows).
2Wire the left branch: 5V → 10kΩ resistor → Node A → LDR → GND.
3Connect a wire from Node A to the Base (B) pin of the transistor.
4Wire the LED branch: 5V → 1kΩ resistor → LED (+) → LED (−) → Collector (C) → Emitter (E) → GND.
5Power on, then cover the photoresistor with your hand. The LED should light up! Uncover it — it should go off.
🔬 The Science: Voltage Divider + Transistor Switch
The 10kΩ resistor and LDR form a voltage divider. In the dark, the LDR's resistance is very high, so most of the 5V appears at Node A — enough to turn on the transistor's Base. The transistor then acts as a switch, connecting the LED circuit and lighting it up.
⭐ Bonus Challenges
• Replace the LED with the buzzer from your Sntieecr kit — make an alarm that beeps in the dark!
• Swap the photoresistor for the thermistor — build a heat-activated indicator instead.
⚠️ Safety Rules
Breadboard voltage: Always use the 5V setting on the power supply module — never higher.
Something feels hot? Disconnect the battery immediately and check your wiring.
Capacitor polarity: Electrolytic capacitors must be inserted with correct + and − legs.
Don't short-circuit: Never connect + directly to − without a component in between.
LED eyes: Don't look directly at a bright LED at close range.
🏆 Progress Tracker
Challenge
Difficulty
Kit
Date Done
Series vs Parallel
★★
Sntieecr
Resistor Explorer
★★
ELEGOO
Dimmer Knob Light
★★★
ELEGOO
Capacitor Fade-Out
★★★
ELEGOO
Auto Night Light
★★★★
ELEGOO
Fill in the date each time you complete a challenge. Go for it, Jeremy! 💪⚡