Circuit Library

A circuit that turns on your garden lights at night. This circuit is connected between the power source of my garden lights and the lights. When the night comes, the lights automatically turn on. In the morning, they turn off again.

This is a gadget that notifies me whenever my daughter tries to sneak out of her room past bedtime. It's based off a standard 433MHz remote control and receiver unit that you can get on Amazon for a few dollars. Check out [the complete tutorial](https://www.build-electronic-circuits.com/door-open-notification-gadget/) for more details.

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 flow so the LED turns on.

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 up of only 4 components. Then you’ll add as many lights as you want.

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 to turn the lamp on/off.

This is a simple project that detects when you got mail! To build it, you need to place a permanent magnet in the lid of your mailbox. And you need to place the reed switch so that it's near the magnet when the lid is closed, but away from the magnet when the lid is open. The LED will turn on after the mailman has opened and closed the lid of your mailbox, indicating that you've got mail!

This project is a a very simple water-leak detector. Place two exposed wires on the floor near your washing machine or some other place where you want to detect leaks. As long as everything is dry, nothing happens. When water reaches the two wires, it conducts just enough electricity to switch a transistor on which turns on an LED.

This is an op-amp circuit that turns on a fan when the temperature goes above a certain threshold. The threshold can be adjusted with a potentiometer.

Never built a circuit before? Then start here. You can build this in a couple of minutes. It's a simple LED circuit that's powered by a 9V battery.

This shows a very simple flashlight project with a LED and a resistor. The switch controls if the light is on or off. Build this into a small casing, and you have yourself a homebuilt flashlight. You can use any battery voltage for this, as long as you adjust the resistor value to match.