There are many uses for RFID such as supply chain management, but access control is one of the most relevant applications for personal use. Many people use RFID access cards to get into buildings, use elevators, or even open the doors to those special penthouse type hotel suites. Setting up your own front door (or any door for that matter) with an RFID enabled access mechanism is pretty easy.
Most access control solutions use an electronic door strike, which gives way when activated so you don’t have to unlock or turn the doorknob; you just push (or pull) the door open. This is exactly what’s used to "buzz" someone in a door. That buzzing sound is AC power rushing through the magnetic coil windings in the door strike, pulling up and vibrating the pin that normally keeps the strike in the closed and locked position. You’re going to use DC power to operate your electronic strike, so all you should hear is a slight click.
There are many different kinds of strikes out there. Figure 1 shows a couple of different products from two different manufacturers. Some are small and expensive, and some are larger and fairly cheap. The important thing is that it fits your doorframe, and uses DC power between 5 and 12 volts to activate. Electronic Deadbolt
If you use a deadbolt to secure your front door, the electronic strike isn’t the best solution. The strike is designed so that you can push the door open without needing to retract the door latch. But when the door closes, the latch in the door is designed to push inward and snap back into place behind the strike. A deadbolt won’t retract when the door closes, it will smash loudly against the strike and possibly damage the door, the strike, the doorframe, or any combination of the three. It would be the same result as if you opened your door, locked the deadbolt with the door open, and then tried to slam the door closed.
One solution to the deadbolt problem involves getting one of those keypad deadbolts like the one shown in Figure 2. It’s a deadbolt that lets you use a standard door key or a number combination entered on a front keypad to retract the deadbolt and unlock the door. If you have a deadbolt in your front door and want to use RFID to get inside, you’re going to need to get an electronic strike and hack up one of these keypad deadbolts as well.
There are actual electronic deadbolts available that function like the electronic strike. They retract when power is applied, but they don’t have the option of unlocking with a standard key. You don’t want to be stuck outside because of a power outage or some other kind of Murphy’s Law type problem, so that kind of electronic deadbolt is out.
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