Step 1: Shopping List
I used two 110V solenoids out of an icemaker, but you may want to build your lock using DC solenoids. Some of them are very strong, and your options for powering the lock in the event of a power outage are greater. Just something to think about. IMPORTANT! -- Make sure you get a continuous duty solenoid, some solenoids are only meant to be energized momentarily, which will cause a problem if you leave them energized and walk away. Read up on the various types of solenoids here.
I got my X10 controller (Keychain Remote type) on eBay for about $15.00 shipped. This is a simple kit that includes the receiver/appliance module and one remote. Search for "X10 Keychain Kit" or "RC6500" on eBay to find the one I bought.
In addition to the above, you'll need 2 return springs per solenoid used, 1/2" steel dowel rod (about $6.00 for 3'), an extension cable long enough to reach your outlet with enough to spare for some additional wiring, and possibly some bits of steel for reinforcement. Depending on what kind of connections your solenoids have, you'll probably want to get some crimp-on connectors. Solder and shrink tubing work better, but are harder to get apart if you should need to.
Optionally, you can buy a couple of magnets to mount inside the recessed mounting hole. This will help the bolt to stay extended, and make a great noise as the bolt closes.
Another improvement on my design would be to use a small hobby box as an enclosure for each solenoid. This would look a lot cleaner and keep the electrical contacts under wraps.
Step 2: Assess your situation
For my door, I had to add a vertical support for the bolt to pass through. I used the left-over wood to make the horizontal mounting surface that the solenoids attach to. I reinforced the vertical pass-through with some framing hardware I found at Home Depot. The strike plates (the metal plates mounted to the door frame) are scrap steel I had laying around. Holes were drilled through the strike plates, steel reinforcements, and wood to accommodate the steel dowel.
IMPORTANT! --Make sure that you line up the holes well before drilling, and check your work after every step to make sure everything still lines up.
Step 3: Assembly
Refer to the picture to see how I attached the return springs to the solenoid. You need to separate the legs of the retainer clip and thread the spring end through before inserting into the pivot pin, bending and clipping the ends off. The other end of the spring will be secured to the mounting surface, but wait until the very end to attach the other end. You may need to make adjustments, and the springs will get in your way.
With the pivot pin, dowel, spring and solenoid all attached now, you'll start to get a better idea how best to mount this up. Take your measurements and figure out the distance of throw on your solenoid. With this information you should now have an idea of how far away to mount the solenoid, and how long you need the steel dowel to be. Now would be a good time to measure, and cut your dowel. If you're planning to use more than one solenoid, you'll need to repeat the above process over again.
Step 4: Mount the Solenoids
Step 5: Wiring
I used a very long PC Power cord for my lock. Any extension cord long enough to get you to your wall outlet should work great. It may be a good idea to route the cord, maybe even secure it along its route before beginning to wire the solenoids. My wiring is depicted (poorly) below. I went with a grounded 3-prong power cord, but haven't yet connected the ground to anything. Once everything is wired, plug the end into a spare power strip (turned off) and turn the strip on to test your wiring.
The image below looks like the white (gray) and black wires cross. They do not in real life. I apologize for the crappy MS-Paint picture, but follow the colors and not the wire paths and you should be good.
Step 6: Connect the X10 Module
Step 7: Connect the Springs!
Since this is controlled by X10, you could easily integrate this into a home automation setup, and unlock your door using a remote, computer, or via a Windows Media or LinuxMCE home theater PC on your television!
Hopefully you're still with me, and this instructable works well for you. If you have any questions, please feel free to leave me a comment, and digg it if you dugg it!
Check out my other instructables!