Circuit Library

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 it will light up an LED when there's a bird moving inside the feeder. A PIR sensor stores an image of the infrared light it sees. Then everytime it sees a change in this image, for example from a bird moving, its output will go HIGH for a period of time.

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 press the Restart button. The specific song used in the example code is a traditional Danish Schnaps song. This project was built to fit into a Schnaps train that brings glasses of Schnaps around the table.

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 to practice your circuit building skills. The circuit is built around a [555 timer](https://www.build-electronic-circuits.com/555-timer/) in astable mode.

This is a simple project where you connect a buzzer to your Arduino to play a melody. You'll use Arduino's tone() function to play different tones and combine into a melody.

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 gets longer for each level. How many levels can you do?

This is a simple traffic light project that simulates the behaviour of European traffic lights: First Red. Then Red + Yellow. Then Green. Then Yellow. This repeats over and over. You can tweak the times for each stage in the code.

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 receiver, a capacitor, a JK flip-flop, and a relay module. You can connect whatever you want to control to the relay, and then use any IR remote control to turn it on or off.

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 the old television show Knight Rider. It's a really fun circuit to build. I once built a larger version of this for the inside of a party bus when I was a teenager. Unfortunately, I broke it the first day because I increased the voltage too much! But that's another story...

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 how many cups of coffee you've had today.

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 [this demo video](https://youtu.be/wSN8_ChDztw) to hear the circuit in action.