This can be used for anything that needs a trigger such as electric screen, projector etc... Also you don't have to use a 12V power supply. Since you're switching the PS on/off with the relay you can use any voltage the relay will handle. In fact it will also switch AC so it can be used to control just about anything as long as it doesn't exceed the specs of the relay.
I made this because I have an Onkyo TX-NR809 Receiver that I use as a Pre/Pro. I use external amps to drive my system's speakers of which I have 3. An ATI 1505, ATI 1502 and Behringer NU3000DSP. None of them have remote trigger inputs. I do however plug everything into a Monster Power Line conditioner/power outlet component which does have a 12V remote trigger input that switches 4 of the outlets.
This receiver has 12V triggers for zones 2+3 but Onkyo in their infinite wisdom did not include a 12V trigger for zone 1 on this receiver nor do I believe on any of their recent receivers! What's a guy to do? Use the unused USB on the back of the unit to trigger it!
How can that be done? Well the Monster will accept 9V-12V to trigger the switched outlets but the USB only supply's 5V. I needed more voltage. So I googled a bit and discovered that a relay is what I needed along with a 12V power source.
Below is a diagram of how this all works. It took me and my non EE brain a bit to understand this very simple circuit. I hope that this diagram will help someone else out there.
So being the overkill guy that I am I decided to make this unit in a project box with individual jacks for all the connections to allow the most flexibility with cable lengths.
Here is the 5V relay module I used. I picked it up on Amazon for under $10. It has connection terminals and PCB mounting holes which made it easy to mount in the box with self adhesive backed stand-offs. There is a High/Low jumper that allows some flexibility on how it's wired too. I used the L setting and jumpered the DC- to the IN terminal to energize the coil.
Here it is wired up before closing the box and then with plugged everything in.
Now when the receiver turns on it powers the USB which in turn activates the 12V signal to the MP. The amps then turn on. When I turn it off the amps turn off.
PROBLEM SOLVED! :grin2: