Circuits
Circuits to build on a breadboard, each with its schematic, layout and parts list.
Dark-enabled Device
This circuit turns on something when it gets dark. It can be light-bulb, a lamp, or something entirely different.
Controlling 5 LEDs
One Arduino pin switches five LEDs together through a BC547 transistor, so the pin doesn't have to supply all the current.
Arduino Memory Game
This is a simple Memory Game game built with Arduino. The point of the game is to repeat the sequence of colors that the Arduino comes up with. The sequence…
Arduino Musical Potentiometer
Turn the potentiometer to set the pitch and press the button to play it on the buzzer: a small Arduino instrument.
Arduino: Buzzer
A passive buzzer connected straight to an Arduino pin, so you can play tones and simple melodies from code.
Arduino with Buzzer and Potentiometer
A potentiometer on an analog input controls the tone an Arduino plays on a passive buzzer.
Simple Rain Detector
This project is a a very simple rain detector. When a drop of water hits the rain sensor board overlapping two neighboring strips, they create a bridge where current can…
Arduino LDR with LED
A photoresistor in a voltage divider tells the Arduino how bright it is, and the LED responds to the light level.
Arduino Light Sensor
A photoresistor and a 1 kΩ resistor form a voltage divider that an Arduino analog input reads as a light level.
Arduino Potentiometer LED
A potentiometer on an analog input sets the brightness of an LED, which the Arduino dims with PWM.
Blinking Holiday Lights
Blinking holiday lights are always fun. This circuit is easy to build and it’s something you can put to use right away. The blinking part of the circuit is made…
Running LEDs (Knight Rider Style)
This circuit creates a light that "runs" back and forth using a 555 timer and a decade counter. It's effect is similar to the light bar on the car from…
555 Timer: Police Lights
This project sets up two flashing LEDs, one red and one blue, to create a police lights effect. You can use this circuit to integrate into a toy, or just…
Arduino Reaction Game
Five LEDs and a pushbutton on an Arduino: press the button at the right moment and see how fast you react.
Arduino Running LEDs
Three LEDs, each with its own resistor, that the Arduino lights one after another to make a running light.
Arduino Button with LED
Read a pushbutton with an Arduino and light an LED while it is pressed. A 10 kΩ resistor keeps the input steady when the button is released.
Arduino Blink LED
The first Arduino circuit: one LED with a resistor on a digital pin, blinking on and off from code.
Plant Watering Notifier (Arduino)
A plant watering notifier built on an Arduino UNO. It monitors soil moisture and lights up an LED when it's time to water. The Arduino reads the sensor value twice…
Plant Watering Notifier (ATTiny85)
A compact, battery-powered plant watering notifier built around the ATtiny85. It monitors soil moisture and lights up an LED when it's time to water. The ATtiny85 spends most of its…
Automatic Night Lamp
This is an automatic night lamp. The lamp turns on automatically at night. Tweak the value of R2 (or replace with a potentiometer) to adjust the amount of light needed…
Universal IR Remote Switch
This project shows you how to create a simple remote-controlled on-off switch that will work with most IR remote controls. And you only need four components to build it—an IR…
Running LEDs
This circuit creates a light that "runs" from one side to the other, using a 555 timer and a decade counter.
Creating Sound (using inverters)
This is an oscillator circuit that will generate a frequency that you can hear and play it on the passive buzzer.
LED Fade In-Out Demo
When this circuit is connected correctly, the light should fade in when you push the button and fade out when you release the button.
Blinking LED (using inverters)
This is a simple LED blinker circuit. Once connected, the LED will flash on and off.
LEDs in parallel
This is a demo circuit that shows how you can connect several LEDs in parallel.
ON-OFF Touch Switch
In this project, you'll build an ON-OFF touch switch with two separate touch switches; one for turning the LED on, the other for turning the LED off.
Light Detector
In this project, you are going to build a light detector. A photoresistor in series with a potentiometer creates a voltage on the base of the transistor that turns the…
Your First Breadboard Circuit
This is one of the simplest circuits to build. It's just a resistor that controls the current through an LED. When you power it on, the LED lights up.
Blinking LED (using 555)
Here's how to build a simple LED blinker using a 555 timer. The 555 timer is configured as an astable multivibrator, which means the output will turn on and off…
Touch-Activated LED
In this project you'll build a touch sensor. When you touch the sensor, your finger acts as a resistor that creates a current through the base of the transistor so…
Scoreboard Display
A simple project that counts the number of times you've pressed the button. Can be used as a scoreboard display for a game. Or to keep tracks of things like…
Secret Code Checker
This is a simple electronic code lock. The output of the lock in this example is a transistor that turns on an LED when you input the right code. But…
Delayed Buzzer
This circuit shows how you can use a capacitor to delay the turning on of a buzzer. For example to wait a few seconds before an alarm sounds after it…
RGB LED Test
This is a simple demo circuit to test the colors of an RGB LED. By pressing different buttons you can mix and match different colors.
Delayed LED
This is a simple demo circuit that will turn on the LED only after a small delay. The delay is decided by the resistor and capacitor. The higher the value,…
Resistors in Series
Imagine that you only have 100 Ω resistors at your disposal and that you want to turn on a 2V LED with your 9V battery. If you connect one 100…
LED Fade In-Out Demo
This is a demo project for fading and LED both in and out. When you press the button, the LED fades in. And when you release the button, it fades…
Flickering LEDs
Three LEDs on Arduino PWM pins 9, 10 and 11, flickering at random like candlelight.
Build your own NOT Gate
This is an example of how to build a NOT gate using a transistor and resistor, also called Resistor-Transistor-Logic (RTL). Basically, this is just a transistor set up as a…
Blinking Many LEDs (with NPN)
A CD40106 inverter oscillator sets the blink rate and a BC547 transistor switches six LEDs at once, more than the chip could drive on its own.
Separate ON-OFF Buttons
One pushbutton turns the LED on and another turns it off. A 555 timer remembers the state between presses.
Basic nMOS Transistor Switch
The basic way to use an nMOS transistor as a switch: a pushbutton on the gate turns an LED on and off.
Automatic OFF Timer
Push the button and the LED turns on, then switches itself off after a while. A 555 timer does the timing, set by a resistor and a capacitor.
Blinking Many LEDs (with nMOS)
An inverter oscillator sets the blink rate and an nMOS transistor switches six LEDs at once, more than the chip could drive on its own.
Creating Sound (using 555)
This projects creates sound for a passive buzzer, or potentially a small speaker. And you can change the frequency by adjusting the potentiometer.
Basic NPN Transistor Switch
A simple demo circuit to test turning an NPN transistor on and off. You’ll use an LED with a resistor to indicate when the transistor is on.
Resistors in Parallel
A circuit to demonstrate that placing a high-value resistor in parallel with low-value resistors won't affect the total resistance in any significant way. No matter how hard you look, you…
Bird Feeder Detector
Do you want to know when there's a bird in your bird feeder? There's a circuit for that! This uses a PIR motion sensor that works with infrared light. And…
Schnaps Song Player
This is a simple circuit to play a song with ATtiny85. It plays the hardcoded song one time at start-up, then stops. To play the song again, you need to…
Relay Blinker Finished
This is a simple circuit for blinking an LED using a relay and a capacitor.
Powering 7 LEDs
This is a demo circuit that shows how to connect many LEDs in parallel.
LEDs in Parallel
Three LEDs connected in parallel, sharing one 1 kΩ resistor and a 9 V battery.
Two LEDs in Series
Two LEDs connected in series with a 1 kΩ resistor and a 9 V battery, so the same current flows through both.
LED Fader Demo
This is a nice demo circuit to build to see the effect that the capacitor adds to a circuit. By using a capacitor, you add a time delay to your…
LED Dimmer Demo
In this experiment, you are going to build a dimmer circuit for an LED. Using a potentiometer, you can change the resistance in a circuit and thereby change the current…
Relay Blinker Ohmify
This is a simple circuit for blinking an LED using a relay and a capacitor.
555 Machine Gun
This "machine gun" circuit generates a sound that mimics the sound of a toy machine gun. It is based around a 555 timer IC in a feedback loop. Check out…