Stories about Software


Adding a Switch to Your Home Automation

Last time in this series, I covered turning a lamp on and off with a keychain. Today, I’m going to up the ante and describe how to control an overhead light with your same keychain. This will be accomplished by replacing the switch for the light that you want to control with a new switch that you’re going order.

The benefits include not only the ability to remotely control the light itself, but also adding dimming capabilities to previously non-dimmable lights. In addition, their “soft” on and off behavior dramatically increases the lifespan of incandescent bulbs.


A few things to check off your list before getting started:

  1. The light to be controlled must be an incandescent light with wattage of at least 40. Do not use on fluorescents, halogens, etc!.
  2. You must have the transceiver from the last post or this will not work.
  3. Needle nose pliers, screw driver(s), wire nuts, wire strippers/cutters, voltage tester.

Also, and perhaps most importantly, you’ll need some degree of comfort changing out a wall socket. I assume absolutely no responsibility for what you do here. Working with home electricity can be very dangerous, and if you are the least bit uncomfortable doing this, I recommend hiring an electrician to wire up the outlet.

Making the purchase

The first thing that you’re going to need to do is order your part. You’re going to want to order the X10 Wall Switch Module (WS467). The price on this varies, but you can probably get it for anywhere from $12 to $20. It is pictured here:

I recommend this one because it will fit into the same space as most existing standard toggle switches. If you are looking to replace a rocker switch, you can order WS12A, which tends to be a bit more pricey, but such is the cost of elegance.


The unit itself will come with instructions, but here is my description from experience:

  1. First, remove the wall plate from the box just to peer in and make sure there isn’t some kind of crazy wiring scenario going on that may make you want to abort mission and/or call in an electrician. This might include lots of different wires using this switch as a stop along the way to other boxes or outlets in the house, for instance. Careful while you do this as your electricity is still live.
  2. Once you’re satisfied that the mission looks feasible, head to your circuit breaker and kill the power. Make sure power is off by using your voltage tester with one lead on the hot wire and the other on ground somewhere (if you didn’t figure out which was hot and which was ground, try both leads on the switch).
  3. Once you’re doubly sure power is no longer flowing, pop the screws on the switch itself that are holding it to the junction box and remove the switch.
  4. Your old switch should have two connected leads, and each of these should have one or more wires connected to each lead. At this point, you can basically just swap the old wireup for the new module’s wireup — the colors don’t matter (though I’ve adopted a convention with these guys of wiring black to hot). You’re going to need your needle nose pliers and wire nuts because unlike most existing outlets, the X10 have wires instead of terminal receptacles.
  5. Once you’ve twisted up the wires and made sure no bare wires are showing anywhere, settle the switch into the junction box and screw it back in. You’re now going to restore power at the breaker box.
  6. When power is back on, verify that pushing the button on the switch turns lights on and pushing it again turns them off. This switch will always be manually operable. Also, don’t be surprised that the lights come on more gradually than you’re used to (it may seem weird at first, but I love this, personally).
  7. Once everything is working properly, you can replace the wall plate. However, in continuation from our first post, what you’re going to want to do now is match the dials on the switch to one of the remote settings, in terms of house code and unit code, before you replace the wall plate. You can always change this later, but you might as well do it now while it’s already off


Now, you’ve got it installed, and it should work manually or from your keychain remote. Generally speaking, wall switches are always operational both manually and remotely. These are not rocker/toggle switches but pushbutton switches, so they have no concept of state. Each time you press the button either on the switch or from the remote, the command boils down to “do the opposite of what you’re currently doing.” That is, there’s no concept of manual or remote push overriding the other — it’s just flipping the light from whatever state it was last in.

In addition to this functionality, you also get dimming functionality. If you hold the button in instead of simply pushing it, the light’s brightness will change. Holding it in when the light is off causes it to ramp up from dim to bright, and the opposite is true when the light is on – it will ramp down. On top of this, the light will ‘remember’ its last brightness setting. So, if I turn the light on by gradually bringing it up from dark and then turn it off, the next time I turn it on, it will ‘remember’ its previous brightness.

One final note is that there is a manual slide below the main switch. This is, in effect, a kill switch. If you push that, you will completely break the circuit and no amount of remote presses or X10 signals can activate it in this state. This is the equivalent of unplugging your transceiver module from the last post. If power is cut, the signals you send don’t matter.


So, now you’ve got a remote control capable of controlling two lights in the house. One is a lamp and the other an overhead light that can now be dimmed and brightened manually, as well as turned on and off remotely. (Next time I install a switch, I will take some pictures of what I’m doing and add them to the instructions above).