Most people know about standby power (i.e. that many electronic devices continue to consume some power even when they are turned off). One way to eliminate standby power is to use a power bar or surge protector with a built in switch to turn off connected devices completely, but these are annoying and rarely get used in practice for 2 reasons:
1. Power bars are usually located under desks or are otherwise obstructed making the switches difficult to access.
2. The power bar switch controls all outlets on the power bar, but sometimes it is desirable to turn some devices off while leaving others on.
I build my own remote power switches to solve both these problems. I can turn off just the outlets I want with a switch placed exactly where I want it. See examples of some of my remote switch installations below. If you have enough mechanical and electrical aptitude to drill a hole and solder two wires together, you can make your own remote power switches too.
For information on this and other projects of mine see my website IWillTry.org.
Step 1: Materials
Here are the materials to make an illuminated remote switch. A non-illuminated remote switch is easier but I prefer this style since it provides visible feedback as to the current status of the electronic equipment connected.
The materials are:
Qty - description - cost
1 - rocker switch Digikey part no CH809-ND - $1.24
1 - plastic enclosure Digikey part no HM375-ND - $1.60
1 - surge protector with removable back cover - $15
6ft - 14 gauge 3 wire electrical cord (should have black, white, and green wires) - $5.00
2 - 2" lengths of 3/16" heat shrink (not shown)
1. Most power bars already have an illuminated switch. You could simplify this project by simply relocating that switch remotely, but I prefer to have a remote switch that only controls some of the outlets on the power bar allowing others to be "always on".
2. Costs for Digikey components decrease with quantity. It will also take you less time per unit if you build several at once. I purchased 10 each of the switches and enclosures for this reason.
3. This particular power bar was for a computer, so I used a surge protected power bar. Non-surge protected power bars are less expensive.
Step 2: Tools
These are the tools I used:
Power drill and 15/64 drill bit
Exacto knife (not shown)
Step 3: Schematic
The image below shows a generic schematic for any power bar. The power bar switch and surge protection circuitry are left out for clarity.
Effectively all you need to do is splice the switch (pins 1 and 2) in series with the hot wire (black) that goes to the outlets you want to control. The switch also contains a light. One side of the light is connected internally to pin 2 and is powered by the hot wire. The other side of the light is connected internally to pin 3 and needs to be wired to the neutral wire (white) inside the power bar.
Step 4: Cut the Enclosure
The hole dimensions required for the switch are 28mm long by 13.5mm wide. Scribe an outline with these dimensions on the side of the housing. Then use an exacto knife to carefully cut away the plastic to the scribe line. Check the switch for fit and adjust as needed.
The electrical cord I used was about 1/4" in diameter, but it could be squeezed through a 15/64" hole for a good tight fit.
Drill the 15/64" hole (or whatever best suits your cord) in roughly the location shown. Precisely locating the hole isn't very important.
Step 5: Wire the Switch Enclosure
Cut the electrical cord jacket back a few centimeters at one end.
Insert the cord through the hole you drilled previously. If you cut the jacket at an angle it will make inserting the cord easier.
Strip about 5mm of insulation off of each wire end. Pre-tin the wire ends and switch terminals with solder. Then solder the wires to the switch terminals as shown in the images and schematic.
Once you are satisfied that you have good solder joints and no stray strands of wire that could potentially cause a short, screw the lid onto the enclosure.
Step 6: Open and Inspect the Power Bar
Some power bars are easily opened by removing some screws. Others are not easily opened. They may be glued or riveted closed. When purchasing power bars, look for those than can be disassembled.
This particular power bar is easily opened by removing 7 Phillips screws from the back.
Once you have the power bar open there are a few things you want to look for:
1. Where is a good place to drill a hole through the side for your remote switch cord to enter?
2. Where is the hot wire (black) that feeds the group of outlets you would like to control?
3. Where is a good place to connect to the neutral wire (white)?
See the image below for the answers to these questions for my particular power bar.
Step 7: Drill a Hole in the Power Bar
Once you've decided on the best location for your remote switch cord to enter the power bar, drill a 15/64" hole in that location.
If the desired location is right on the seam where the two halves of the power bar housing meet, just reassemble the power bar before drilling. Be careful not to drill any deeper than you need to.
Step 8: Wire the Remote Switch to the Power Bar
Cut the electrical cord jacket back as much as necessary to have a reasonable length of wire to work with inside the power bar. In my case this was about 6".
Strip each of the three wires in the cord back about 5mm and pre-tin them with solder.
Cut the hot wire (black) in the power bar that you chose in an earlier step.
Strip the two cut ends back about 5mm and pre-tin them with solder.
Slide some appropriately sized heat shrink over the black and white wires of the cord and solder these wires to the black wire ends in the power bar. Make sure the black cord wire goes to the hot side of the black cut wire in the power bar. Likewise, the white cord wire should go to the outlet side of the black cut wire in the power bar.
After confirming good solder joints, slide the heatshrink down the wires over the joints and shrink it. Preferably you should use a heat gun, but you can also use a hair drier or the soldering iron itself (it just takes a bit longer and is a bit smellier).
Solder the green cord wire to the neutral (white) wire inside the power bar at the location you picked earlier.
Step 9: Re-assembly, Testing, and Savings Calculations
Reassemble the power bar making sure your wires are out of the way of all outlets and screw mounts and that the two pieces of the power bar housing still fit together nicely.
It's a good idea as a first test to plug the power bar into another power bar. That way if you inadvertently short circuited anything, you'll just trip the power bar breaker instead of your house circuit breaker.
Try plugging a lamp or other appliance into each outlet and test if you can control the outlets you want. Also check to see that the switch illuminates correctly (if it is always illuminated, then you swapped pins 1 and 2 in the schematic).
You may also wish to label which outlets are "switched" and which are "always on". It doesn't take long to forget.
Let's assume that an average remote power switch installation eliminates 15W of standby power. Assume further that the equipment is in use 40 hours a week (an office computer setup for example). Therefore, there are 128 hours a week when the equipment would normally have been in standby mode. That corresponds to 99.84 kWh per year. At roughly $0.07 per kWh (the price where I live), that is a savings of about $7.00 per year.
Therefore the time till payback on materials alone is at least a couple years. It's probably 5-6 years if you value your own time at a reasonable rate. But it does pay back eventually, and if you are running a lot of equipment (for example if you have a home business) the savings start to become significant.
There's also the convenience and coolness factor of turning off multiple pieces of equipment with a custom mounted illuminated switch. Honestly... you'll be surprised how much fun you'll have turning your equipment on and off once you install one of these switches.
For information on this and other projects of mine see my website IWillTry.org.