gallery · 34 circuits
Circuits you can open and run.
Every circuit here loads onto the live breadboard with one tap — flip its switches, swap its parts, break it, save your own version. The library is curated; the rest were shared by builders like you.
The library
First LightA flashlight. Tap the switch to open and close the loop.
Morse Code MessengerKey up, LED dark. Tap the switch to send dots and dashes.
Tabletop Traffic LightThree LED lanes in parallel, all lit together by one switch. For the sequence, see Traffic Light Sequencer.
Brightness LabTwo lanes: tap lane B's resistor to cycle values and compare.
Automatic Night LightDarken the room and the transistor switches the LED on.
The VaultTwo keys in series. Both must be turned for the light.
Sunrise AlarmThe night light's divider flipped: light wakes the LED.
Dial-a-BrightnessA 10 kΩ pot in series with a 220 Ω safety resistor. Tap the pot to turn the knob and watch the LED fade.
Cookie Jar AlarmOpen the lid (bright room) and the buzzer sounds.
DoorbellPress the button: buzzer plus a headphones-on light.
Push-Button FanHold the button and the motor spins. Flip the battery to run it backwards.
DimmerA 10 kΩ pot in series with the LED. Tap it to turn the knob.
One-Way StreetA diode only passes current one way. Tap it to turn it around.
Too-Hot AlarmWarm the thermistor (slide the temperature up) and the LED comes on.
Slow FadeHold the button to charge the capacitor. Let go: the LED fades out.
555 BlinkerThe classic 555 astable. Watch the capacitor's sawtooth on the scope.
One-Shot Timer555 monostable: tap the button and the LED stays on for about a second.
Pitch ControlA 555 at 480 Hz into a piezo. Tap the pot on the CTRL pin to change the pitch.
Traffic ControllerThe traffic light with a switch per lane. You run the sequence: red, green, amber.
Traffic Light SequencerA 555 clock steps a 4017 counter: red, green, amber, repeat. The real thing.
Do Not Disturb SignA green "chill" LED plus a switched red "leave me alone" LED — two lanes on one battery, and a switch that only touches one of them.
Handhold ChainThree switches in a line — the LED only lights when all three are closed at once. AND, one step past The Vault.
Two-Door SignalTwo slide switches in parallel, one shared LED — either switch alone lights the lamp. The OR gate, at Level 1.
Continuity TesterYour first real tool — two probe wires that beep and light up whenever the tips touch anything that conducts.
Panic DoorbellTwo buttons wired so either one fires the same buzzer and light — your first OR gate.
Two-Tone DoorbellTwo call buttons, one doorbell: LOUD rings the buzzer and lights the porch LED; QUIET starves the buzzer and shows why it can't just be dimmed.
Whisper AlarmA doorbell with a volume knob — the pot lives in the buzzer lane, so twisting it changes the beep without touching the light.
Curfew BeeperThe Automatic Night Light's brain with a buzzer where the LED used to sit — beeps the moment the room goes dark, so you never miss sunset.
Fever BeeperThe Warm Hand Alarm's brain wired to a buzzer instead of a lamp — silent in a normal room, beeping the second a warm palm covers the sensor.
Reading LightThe Automatic Night Light with a knob on top — turn it to dial in how dark the room has to get before the lamp fires. Your first tunable threshold.
Study LampThe Automatic Night Light with a force-on override — flip the slide switch and the lamp stays lit even in daylight, ignoring the sensor.
Trip Wire AlarmA thin wire across a doorway holds the alarm silent. Break the wire and the buzzer screams — until you connect it back.
Vacation NightlightThe Automatic Night Light with a manual override — flip the slide switch off and the lamp stays dark even in a pitch-black room.
Warm Hand AlarmCup your hand over the sensor and the LED lights up — a thermometer that turns into a switch.
Shared by builders
Nothing shared yet. Build something on the Workbench, save it, and tap Share — it shows up here.