Automatically Turn Off the Power Strip of the Computer (monitor, Speakers, Etc.) When You Shut Down the Computer.

If you have a desktop computer at home, you will know better than me how boring it is to turn off the power strip of your computer every time we click on "shut down" to turn off monitors, speakers, any lights and so on.

Since I went through this situation before this project, today we are going to see together how to build a relay module that keeps all the devices of the desk on until the computer is turned off (even after an update).

To turn on the computer we have to press the button to bridge between "normally open" and "common" of the relay to turn on the computer (if you have the ignition from AC Back from the bios) and after this, the 5V of the USB will keep the relay powered and also the computer and the desk devices.

When we turn off the computer or after an update, the computer will shut down and remove the power from the USB which will de-energize the relay which will not keep the contact closed and everything (monitor, speakers and any lights) will turn off with it.

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• prototype board to solder (optional but highly recommended)
• 5V relay - 250V 3A
• Terminal connectors
• A USB cable
• A Push button 250V 10A
• Hot Glue

First of all, like all electronic projects, we need a drawing of a circuit that we will then build.

It is not only necessary to design the circuit but it is also very important to understand it in order to solve the problems at the source and not when we have already soldered everything.

In the circuit in the picture we have, starting from the left, the usual DC jack which will be connected to a male of the same jack which will finally be connected to the USB which will be connected to the computer.

I put this connector into the project because I have already put such a system in my workstation to turn on the modem when I turn on the computer and not to use two USBs. I need the jack to disconnect the relay module to move the desk but in your case I don't think you need it.

To the right, we find the heart of the system ... the 5V relay which supports a voltage of 250V and a current of 10A. Now there are thousands of these relays everywhere (for example, I unsoldered it from a sonoff basic on which I did not need the relay)

Obviously the relay must be for 5V so that it turns on without getting too hot. If we choose it with too high ignition voltage, it will not turn on. If we choose it with too low ignition voltage, it will turn on of course... enough to make flames!

Another thing to pay attention to is the size of the internal contacts. 10 amps for such a job are just fine but don't go below that value because otherwise the metal sheet that moves when the relay turns on would be too thin to carry the current load given by the computer, monitor, etc.

Finally, we find the last component which are nothing more than electrician clamps (in the photo there is an error: you see two of them but they are in parallel, put only one clamp of course)

After taking all the components, solder them in the same position as the schematic on the prototype board.

And it's done! It is a very simple circuit that, if you have the components, I suggest you replicate at least three times because it can be very useful.

Since you had to make traces on the prototype board, you will need to isolate the contacts and to do that, for this project (since I didn't want to put it in a box) I used hot glue.

In fact, when the circuit was finished, I turned it upside down and with electrical tape I created walls around the edges of the board of 3/4mm. After that, I warmed up the hot glue well and poured the glue from the top and waited for it to dry.

Once it dried, I removed the electrical tape and a beautiful layer of glue came out that insulates the board very well (as you can see in the photo).

The last steps are: mount the button that gives the ignition impulse to the computer and finally connect the USB to the computer.

As you have seen, it was very easy to make this circuit which is very functional. Obviously to make everything work you have to activate the option that turns on the computer when it is connected and also (but it should already be on) the option that turn the USB off when pc turns off (functions that are very easy to find in the BIOS).

I hope you liked it!