One of my small but very useful DIY projects was modifying a standard 230V power strip so it automatically turns on and off together with my PC. The goal was simple: power my 2.1 audio system only when the computer is actually on, without having to manually flip a switch every time.
I started with a normal 230V power strip equipped with a mechanical on/off switch. After disassembling it, I removed the original switch entirely. Instead of replacing it with a relay PCB board.
In place of the original switch, I installed a custom PCB with a 5V relay. The relay is wired so it switches the mains line exactly like the original power switch did, but now it’s controlled by a low-voltage signal.
To power the relay, I connected it to a 5V USB cable. This way, when the PC provides 5V, the relay closes and the power strip turns on. Simple and effective.
I realized a limitation of my PC, unfortunately, the USB ports on my motherboard remain powered even when the PC is turned off. This meant the power strip stayed on all the time, defeating the whole purpose. Some BIOS setups allow disabling USB power when the PC is off, but in my case, that option simply wasn’t available.
To fix this, I redesigned the activation method. Instead of relying on USB power, I created a custom adapter from an internal PC power supply connector to a 2.5mm DC power jack mounted on the back of the power strip.
Now the relay gets its 5V directly from the PC’s internal power supply, meaning it only receives power when the PC is actually on. When the PC shuts down, the relay releases and the entire power strip turns off automatically.
Notes
- read risk disclaimer
- excuse my bad english
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