Smart Socket USB – Power on Demand

I built a simple and efficient system to sync my soundbar’s power with my TV, eliminating unnecessary energy waste. Using a USB-powered relay (connected to the TV), the soundbar now turns on/off automatically with the TV—no smart home systems or idle power consumption needed. A practical, wired, and eco-friendly solution!

Why It Works:

- Eco-friendly: Eliminates standby power waste.

- Plug-and-play: No apps, cloud, or smart devices.

- Reliable: Mechanical activation via the TV’s USB signal.

The entire project is built with recycled parts, except for the relay board which I bought for less than 1 euro.

Reference for Purchase: 1-Channel 5V Relay Module with Optocoupler ( jumper set to high-level trigger )

Removing Plastic Ribs with a Dremel to Fit the Relay Board

Electrical connections

1. Connected the +5V DC pole to the relay's input signal (IN)
2. Secured the USB cable's +5V and GND wires to the screw terminal using ferrules (shown in white) for reliable contact
3. Other side relay board's:
4. Used COM and NO ( normally opened ) terminals
5. Wired a 230V cable to the power cord

Mechanical mounting

1. Secured the relay board in place using hot glue ( marked by arrows in the figure )

Simple automatic control using TV power state

When the TV is turned on, it powers the USB port → this sends a +5V signal to the relay's control pin (IN) → activating the relay → which closes the 230V AC circuit → supplying power to the electrical plug.

See this short test video, I power on a vacuum tool to verify operation. Enjoy!