[How-To] Make a Relay Power Switch


Cocooner rrockoff (Rod) was kind enough to submit this How-To on making a relay power switch. His submission is detailed below:

How-To Make a Relay Power Switch

by rrockoff

Background: I am almost done adding a 7.1 surround system to my master bedroom with 2 extra music zones (bathroom and retreat). My 7.1 receiver has a powered zone 2 but zone 3 needed an amplifier. Lucky for me I had an old amp in my junk pile waiting to be used. I wanted the external amp to power on when the main 7.1 receiver is turned on. However, the max output of the switched plug on the back of the receiver is only rated at one amp. My external amplifier is rated at four amps. A $10 trip to hardware and Radio Shack fixed my issue.

I used the following parts to make a relay switch. You may need different parts depending on what you have laying around your house. Also I am not an electrician. I do not take any responsibility for any issue that can result from making this DIY project.

Materials Required
  • Six Outlet Power Strip
  • 12VDC relay - rated at 10A at 120VAC (Radio Shack part number 275-248)
    --You may want to use a different relay depending on the wall wart you use. --
  • 12VDC wall wart
    -- Use whatever you have. Mine just happens to be 12VDC 300ma. --
  • Msc. Wire
  • Soldering Iron
Here is how it works:

(Click on Picture for Full Sized Image)

12 volt wall wart plugged into the 7.1 switched outlet in the back of the receiver. Other end of wall wart (12VDC) connected to the coil of the 12VDC relay. Hot wire connected to Normally Open connections on relay. With this simple configuration, the power strip only turns on when the receiver turns on. Since the power strip is plugged into the wall, I get around the one amp limitation of the receiver.

I realize there may be better ways to accomplish this same task. This was just the quickest and easiest way for me. My hope is that you may see this idea and modify it to work for your own situation.

Step 1. Open up the power strip. There were 6 phillips head screw on the back of my power strip.

(Click on Picture for Full Sized Image)

Step 2. Solder approximately 2 inches of wire to the center contact for the coax power jack and 2 inches of wire to the shell contact.

Step 3. Drill a hole in the plastic housing of the power strip. The hole will need to be the same diameter as the end of the coax power jack. This is the location that the coax power jack will be presenting itself to the outside world.

(Click on Picture for Full Sized Image)

Step 4. Solder the opposite ends of the wire from step 2 to the coil connections on the relay.

(Click on Picture for Full Sized Image)

Step 5. Cut the black wire connecting from the power cable to the power cable to the power switch.

(Click on Picture for Full Sized Image)

Step 6. Solder the one end of the wire cut in Step 5 to the NO (normally open) connector on the relay. Solder the other end of the wire cut in Step 5 to the Com (common) connector on the relay.

Step 7. Wrap all solder connections with electrical tape. I actually used shrink tub for this.

Step 8. Mount the coax power jack in the hole from Step 3.

(Click on Picture for Full Sized Image)

Step 9. Reinstall the back cover of the power strip.

Step 10. Test your work.

Step 11. Connect the parts per the first picture.