Main Features Contactless operation 90-100mm detection range No batteries (in tags) to go flat Stores up to 24 tag ID codes Easy tag addition & removal Works through any non-metallic material Audio feedback via on-board beeper Tamper detection Arm & alarm outputs Electric door strike output Suitable for home or car use Requires 12V DC @ 40mA (nominal)

Many home security systems include a keypad situated at the main point of entry or exit. More complex systems may also include a battery-powered remote control device. While these systems have their own merits, they can also be more than a little inconvenient.

Having to punch in a code repeatedly can be quite irritating, as can the discovery that the batteries in the remote have finally given up the ghost! This new point-of-entry system solves these problems because it requires no physical contact and no batteries.

Essentially, the system consists of a reader module and one or more "tags". Based on RFID (Radio Frequency Identity) technology, each tag is encoded with a unique identity.

When a tag is brought within range of the reader, it is energised by the reader’s magnetic field. It then transmits its unique code to the reader, which validates the code and arms or disarms the alarm system accordingly.

This system also includes the ability to operate an electric door strike. A simple wave of your hand and an "Open Sesame" incantation are all that are required for the door to your castle to spring open! Well – the "Open Sesame" incantation isn’t really necessary.

System overview

The RFID Security Module is built on a single PC board measuring just 50 x 70mm. In fact, it’s small enough to be concealed behind a standard Clipsal wall plate or similar. It can be operated as a stand-alone keyless entry system or as part of a larger alarm system.

Three open-collector outputs and a single digital input are accessible via a 4-way terminal block. One of the outputs is designed to drive a 12V DC solenoid-actuated door strike. These are available from major kit suppliers and most security equipment resellers.

The two remaining outputs can be hooked into an existing alarm system to supplement or replace an existing point-of-entry keypad or other remote control device.

The digital input can be wired to a tamper switch to detect removal of the cover or the unit from the wall.

To cater for varying installations, the module can be programmed to operate in one of four modes, as follows:

Mode 1: no alarm features (keyless entry only), door strike energised on tag validation.

Mode 2: alarm operation, door strike energised on disarming.

Mode 3: alarm operation, door strike energised on arming.

Mode 4: alarm operation, door strike energised on arming and disarming.

In most cases, the RFID module will be mounted outside the protected perimeter, so you’ll want the strike to be energised on disarming (mode 2). The desired operating mode is selected by performing a simple initialisation procedure, as we’ll see a little further on.