The switch, and what open really means
A slide switch in the middle of a loop. Find out what a break in a circuit does, why the switch can go anywhere in it, and what a floating wire is.
Open it in the simulatorAll paths
Electronics basics
A breadboard and a few parts, with one Uno blink at the start and no processor after it. What current, voltage, time and logic really do.
0 of 20 done
What you will build
6 projects, built step by step
20 lessons in 11 chapters, about 10 hours on a simulated breadboard. Free, in your browser, every step checked by the simulator.
Branches in parallel
Two LED branches across the same supply. Each one sets its own current, the supply carries the total, and two resistors side by side come out smaller than either.
Open it in the simulatorA light sensor is a divider that moves
A light-dependent resistor changes its resistance with light. Put it in a divider and the voltage tells you how bright the room is.
Open it in the simulatorChoosing R and C for a delay you want
The same circuit, used the other way around: start from the delay, pick the parts, and find out which of the two you should change.
Open it in the simulatorThe 555 with a reset pin
The same astable, gated by a button on the reset pin instead of switched in the supply, driving a buzzer. Why gating a chip beats switching a load.
Open it in the simulatorFlip-flops that count
A D flip-flop wired to toggle halves a clock. Four of them in a chain count in binary, and the lamps spell out the number.
Open it in the simulatorThe map
Chapter by chapter
Each lesson opens when the one before it is done, and each chapter ends in a project.
Chapter 1
The first loop
Wire a loop by hand, let an Uno blink it, then read a circuit as a loop and light an LED on purpose.
- Open165 XP
Build your first circuit
Start with the parts in place. Draw every wire yourself, close the loop, press Run and light the LED.
0 of 5 steps
- Locked140 XP
Make it blink with an Uno
Two wires from an Arduino Uno to the LED you already know, then press Run and let a program do the switching. Four steps, no code to write.
0 of 4 steps
- Locked160 XP
A first circuit
One loop on a breadboard: five volts, a pushbutton, a resistor and an LED. Build the habit of reading a circuit as a loop, and work out the current in it.
0 of 6 steps
- ProjectLocked340 XP
The switch, and what open really means
A slide switch in the middle of a loop. Find out what a break in a circuit does, why the switch can go anywhere in it, and what a floating wire is.
0 of 7 steps
5 questions, graded as you go.
Chapter 2
Ohm's law
Volts, amps and ohms in one equation, and how to use it backwards to pick a part.
- Locked160 XP
Ohm's law: volts, amps and ohms
One resistor across 5 V. Change the resistor and watch the current change, then pick a resistor for a current you want. The one equation behind every circuit.
0 of 6 steps
4 questions, graded as you go.
Chapter 3
Series and parallel
The two ways to join parts, and the sums that go with each.
- Locked170 XP
Resistors in series
Two resistors nose to tail with an LED. One current everywhere, resistances that add, and voltages that share themselves out in proportion.
0 of 7 steps
- ProjectLocked340 XP
Branches in parallel
Two LED branches across the same supply. Each one sets its own current, the supply carries the total, and two resistors side by side come out smaller than either.
0 of 7 steps
5 questions, graded as you go.
Chapter 4
Dividers and sensors
Split a voltage in a ratio you choose, then let a light sensor move the ratio.
- Locked160 XP
The voltage divider
Two resistors in a row split a voltage in a fixed ratio. Read the middle with a meter, change the ratio, and build a divider for a voltage you choose.
0 of 6 steps
- ProjectLocked320 XP
A light sensor is a divider that moves
A light-dependent resistor changes its resistance with light. Put it in a divider and the voltage tells you how bright the room is.
0 of 6 steps
4 questions, graded as you go.
Chapter 5
The capacitor and RC timing
A part that takes time, and how to choose how much time it takes.
- Locked170 XP
Charging a capacitor
A resistor, a capacitor and a switch. Watch a voltage take time to get somewhere, and learn the one number that says how long.
0 of 7 steps
- ProjectLocked370 XP
Choosing R and C for a delay you want
The same circuit, used the other way around: start from the delay, pick the parts, and find out which of the two you should change.
0 of 7 steps
5 questions, graded as you go.
Chapter 6
The transistor switch
A trickle into one leg switches a much bigger current through the other two.
- Locked145 XP
The transistor as a switch
A tiny current into the base switches a big current through the collector. Switch an LED with a transistor and measure how much smaller the control current is.
0 of 6 steps
4 questions, graded as you go.
Chapter 7
Power from the wall
Four diodes and a capacitor turn the wall's AC into steady DC.
- Locked135 XP
From the wall to DC: a rectifier and a capacitor
One diode blocks the negative half of an AC wave, and a big capacitor fills the gaps. Watch AC turn into smooth DC, and see what a small capacitor or a heavy load does to it.
0 of 5 steps
4 questions, graded as you go.
Chapter 8
The op-amp
Two resistors set the gain of an amplifier, and the supply sets how far it can go.
- Locked110 XP
The op-amp: a gain you can choose
Two resistors set the gain of an inverting op-amp amplifier. Turn a tiny wave into a big one, then push the gain until the top and bottom get chopped flat.
0 of 4 steps
4 questions, graded as you go.
Chapter 9
The 555
Turn an RC into a square wave, and gate it with a button.
- Locked160 XP
Timing with no processor: the 555
A resistor, a capacitor and a 555 make a square wave with no code in sight. Measure it, then change the parts to change the rate.
0 of 6 steps
- ProjectLocked370 XP
The 555 with a reset pin
The same astable, gated by a button on the reset pin instead of switched in the supply, driving a buzzer. Why gating a chip beats switching a load.
0 of 7 steps
5 questions, graded as you go.
Chapter 10
Logic gates and a latch
Decisions in nanoseconds, one bit of memory, and four flip-flops that count.
- Locked145 XP
Gates, as real chips
AND, XOR and NOT with two buttons and three lamps. Fill in the truth tables by pressing, and find out what a real chip has that the symbol does not.
0 of 6 steps
- Locked145 XP
One bit of memory
Two NAND gates wired into each other hold an answer after the input goes away. The smallest memory there is, and the reason a switch stops bouncing.
0 of 6 steps
- ProjectLocked290 XP
Flip-flops that count
A D flip-flop wired to toggle halves a clock. Four of them in a chain count in binary, and the lamps spell out the number.
0 of 6 steps
5 questions, graded as you go.
Chapter 11
The shift register
Three wires in, eight outputs out, and as many more as you chain on.
- Locked145 XP
Eight outputs from three wires
A 74HC595 driven by a clock and a switch, with no processor anywhere. Load a pattern by hand, watch it march, and find out what the latch is for.
0 of 6 steps
4 questions, graded as you go.
Syllabus
Every lesson in the course
All 20 lessons, in order, each with what it covers. Any of them opens in the editor right away.
The first loop
- Build your first circuitStart with the parts in place. Draw every wire yourself, close the loop, press Run and light the LED.
- Make it blink with an UnoTwo wires from an Arduino Uno to the LED you already know, then press Run and let a program do the switching. Four steps, no code to write.
- A first circuitOne loop on a breadboard: five volts, a pushbutton, a resistor and an LED. Build the habit of reading a circuit as a loop, and work out the current in it.
- The switch, and what open really meansA slide switch in the middle of a loop. Find out what a break in a circuit does, why the switch can go anywhere in it, and what a floating wire is.
Ohm's law
- Ohm's law: volts, amps and ohmsOne resistor across 5 V. Change the resistor and watch the current change, then pick a resistor for a current you want. The one equation behind every circuit.
Series and parallel
- Resistors in seriesTwo resistors nose to tail with an LED. One current everywhere, resistances that add, and voltages that share themselves out in proportion.
- Branches in parallelTwo LED branches across the same supply. Each one sets its own current, the supply carries the total, and two resistors side by side come out smaller than either.
Dividers and sensors
- The voltage dividerTwo resistors in a row split a voltage in a fixed ratio. Read the middle with a meter, change the ratio, and build a divider for a voltage you choose.
- A light sensor is a divider that movesA light-dependent resistor changes its resistance with light. Put it in a divider and the voltage tells you how bright the room is.
The capacitor and RC timing
- Charging a capacitorA resistor, a capacitor and a switch. Watch a voltage take time to get somewhere, and learn the one number that says how long.
- Choosing R and C for a delay you wantThe same circuit, used the other way around: start from the delay, pick the parts, and find out which of the two you should change.
The transistor switch
- The transistor as a switchA tiny current into the base switches a big current through the collector. Switch an LED with a transistor and measure how much smaller the control current is.
Power from the wall
- From the wall to DC: a rectifier and a capacitorOne diode blocks the negative half of an AC wave, and a big capacitor fills the gaps. Watch AC turn into smooth DC, and see what a small capacitor or a heavy load does to it.
The op-amp
- The op-amp: a gain you can chooseTwo resistors set the gain of an inverting op-amp amplifier. Turn a tiny wave into a big one, then push the gain until the top and bottom get chopped flat.
The 555
- Timing with no processor: the 555A resistor, a capacitor and a 555 make a square wave with no code in sight. Measure it, then change the parts to change the rate.
- The 555 with a reset pinThe same astable, gated by a button on the reset pin instead of switched in the supply, driving a buzzer. Why gating a chip beats switching a load.
Logic gates and a latch
- Gates, as real chipsAND, XOR and NOT with two buttons and three lamps. Fill in the truth tables by pressing, and find out what a real chip has that the symbol does not.
- One bit of memoryTwo NAND gates wired into each other hold an answer after the input goes away. The smallest memory there is, and the reason a switch stops bouncing.
- Flip-flops that countA D flip-flop wired to toggle halves a clock. Four of them in a chain count in binary, and the lamps spell out the number.
The shift register
- Eight outputs from three wiresA 74HC595 driven by a clock and a switch, with no processor anywhere. Load a pattern by hand, watch it march, and find out what the latch is for.
Keep going
The next course on your track
Electronics basics is part of the electrical track, a ladder of courses from zero to expert.
Digital logic and memory
Build logic from individual gates, then make a bit persist, count and move through a register.
Open the next courseElectrical track
Current and voltage you can see, then transistors, op-amps, filters, power and PCBs. Every circuit runs in a real circuit simulator in your browser.
See every course on the trackKits
Build it on your bench too
Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts.
Find your kit
Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins.
See every kitQuestions
About Electronics basics
Is Electronics basics free?
Yes. All 20 lessons of Electronics basics are free and run in your browser, with nothing to install and no parts to buy before you start.
Do I need any parts?
No. Every circuit is built on a simulated breadboard, and the simulator checks each step as you go. When you want to build it for real, the same parts and wiring work on a real bench.
How long does Electronics basics take?
About 10 hours: 20 lessons in 11 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off.
What will I build?
Each chapter ends in a project that puts it together: The switch, and what open really means, Branches in parallel, A light sensor is a divider that moves, Choosing R and C for a delay you want, The 555 with a reset pin and Flip-flops that count.
Where do I start?
With "Build your first circuit". This course starts from zero: no electronics or code needed before it.