Sound Activated Outlet

The Clapper was a popular gadget in the 80’s and 90’s. It let you turn appliances on and off just by clapping. This can be pretty useful, but it has some limitations. First there is the problem of loud noises accidentally turning the lights off. Also, you can’t control multiple outlets independently of each other.
So I decided to make programmable version of the Clapper using an Arduino microcontroller. The Arduino lets you set codes for each outlet. This eliminates false triggering and lets you control multiple outlets independently. Your lamp could be turned on and off with one clapping pattern and your fan could be controlled with another pattern.
The Arduino also lets you program how the outlets are turned on and off. For instance, if your internet router needs to be reset, you could program it to turn your internet router off for ten seconds and then turn it back on automatically. Or you could turn a heater on for a few minutes and automatically turn itself off.
Sound Activated Outlet

Step 1: Watch the Video

Here is a video walkthrough of the project.

Step 2: Materials

Here are the materials and tools that you will need for this project.
Arduino microcontroller
Electret microphone
2 x 10 kohm resistor
100 kohm resistor
3 x 100 ohm resistor
0.1 microfarad capacitor (capacitor code 104)
White LED
Green LED
Small Switch
Jumper wires
Power MOSFET (such as IRF510)
Diode (rated for at least 1 amp)
5 Volt Relay
Extension cord
printed circuit board
Insulated project enclosure
5V power supply/ USB charger
Soldering Iron and solder
Wire Cutters
Wire Strippers
Screw Driver

Step 3: The Circuit Design

The circuit for this project can be divided into two main parts. There is a microphone assembly and a relay driver.

The microphone assembly is composed of an electret microphone element, two resistors and a capacitor. When the microphone picks up sound vibrations, the output voltage fluctuates in response. This signal is sent to one of the analog input pins on the Arduino.

The relay driver is composed of a power MOSFET transistor, a diode and a relay. The power transistor is added because the relay requires more current than the digital pins on the Arduino can output. So the output signal that is sent from the digital pin activates the transistor and the transistor connects power to the relay and turns it on. The relay either connects or disconnects power from the AC outlet to the attached appliance. The diode acts as a suppression diode and protects the Arduino from voltage spikes that occur when the relay is turned off. If you don’t want to build a relay driver from scratch, you can use a commercial relay shield or a Power Switch Tail.

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