This instructable will walk you through the process of dismantling and hacking a Schlage electronic deadbolt in order to control it with an arduino.
Step 1: Purchase the Lock and Unpack It
I got mine on sale for $99 at Lowe's.
Remove it from the box and take a look at what's there. The construction of the lock is really great. Anywhere that could even remotely see any moisture is surrounded with rubber sleeving or a rubber o-ring. The lock has 3 basic parts:
outside portion: This portion has a regular key cylinder, a knob for the deadbolt similar to what you normally see inside of a house, and a keypad for entering the code.
inside portion: This portion has a knob to operate the deadbolt, a housing for a 9v battery, and a switch to tell the electronics in the front of the lock when the lock is in use.
deadbolt mechanism: This portion is similar to any other deadbolt on the market.
Step 2: Take the Faceplate Off of the Lock
Turn the outside portion over and you'll see 6 #2 phillips screws. Remove them and you should see something like the second picture.
Step 3: Take the Intermediary Plate Off
Flip the outside portion over and you'll see what's in the first picture.
remove 2 T10 Torx screws seen in the second picture and you'll have something like what's in the third and forth pictures.
Step 4: Check Out All of the Neat Stuff
You should see the backside of the intermediary plate as well as the part of the mechanism that actually does the locking.
If you weren't careful, the long thin part that goes through the middle portion likely pushed its way out a bit and an almost invisible spring went shooting somewhere. Go find it. We'll call this assembly the working portion. Picture 2 displays how it goes together.
On the right you'll see a piece of plastic that resembles a backwards C. This piece of plastic uses a post on its backside between two coils of a spring attached to a motor. When it moves up, it pushes the mushroom shaped part of the working portion upwards causing the "stem" of the mushroom to stick out into some of the fingers of the star shaped piece on the rear of the intermediary plate. This allows the knob on the front of the lock to turn the working portion and operate the deadbolt.
It's pretty simple but very effective. Motor spins in one direction, plastic goes up and the lock works. Motor spins in the opposite direction, plastic goes down, lock freewheels.
In the next step, I'll show how to attach some wires to the motor so you can control them.
Step 5: Wire It Up!
Pull the control pad off of the motor and examine the rear. You'll see a black wire and white attached to the small motor. These are isolated from one another via the microcontroller on the Schlage circuit board so just find some small wiring ~24AWG and solder one to each post.
Carefully route these two wires around the Schlage circuit board and push them through the rubber sleeve so you'll have access to them once the lock is reassembled.
Step 6: Reassemble the Lock
Put the working portion in, put the intermediary plate on and then put the face plate back on the lock.
You should be able to use a 9v battery to control the lock's function.
Step 7: Create H Bridge Circuit
Follow this schematic and create your H bridge circuit.
You should now be able to pick any two digital outs on the arduino. Setting one low and one high will operate the lock's motor in one direction and obviously if you do the opposite, the motor will operate in the opposite direction.
I added a Parallax RFID reader and I can use the Schlage's keypad or an RFID card to open the lock.
I also am developing a new security product, Tactcess, that I've interfaced with the arduino.
Read more here: http://www.cribbstechnologies.com