So i wanted to have some of my peripherals turn off when my computer is off. Speakers and lamp and such. I made a simple one using USB power to switch on/off a power strip but modern PCs have USB powered on always. So without some intelligent circuitry, this will no longer work.
So what i use now is a power strip controlled by the PCs power supply. Essentially I have a relay that switches when the computers power supply is on. But with some added protection, so I wont damage anything inside the PC.
The PCs power supplies “12V” output is hooked into an isolation DC-DC converter, then a linear regulator. This protects the PC if there is a short or if the external wires touch a high voltage by accident. I put these all on a card to make it pretty, and more convenient. After the protection circuit a cable connects to the power strip. Inside the power strip a relay is controls the hot line of the power strip. I used a small power strip to save space and to remind me not to plug too much into it.
- Molex 8981 – Disk Drive Power Connector
- Digikey Molex 8981 Series connectors
- I took one off an old CDROM drive.
- VB1212LS-1W – Isolated 12V-12V DC-DC converter
- VB1212LS datasheet
- You can use any isolated DC-DC converter that allows Vin=12V and Vout>6.5V and max power > 0.1W
- 5V linear regulator
- You can use any 5V linear regulator or LDO that allows Vin=12V
- 5V relay
- You can used any 5V relay with switch voltage>=110Vac
- Note that the max switch current of the relay is the max current you can use on the power strip
- I used a 4.5V relay, because that is what I had. If you use a 5V relay remove the diode, “diode1”
- Can use any switching or rectifier diode. I used 1N914
- 1uF capacitors
- I used 1uF electrolytic capacitors
- Power strip