Archive for the ‘RFID’ Category

Arduino Wiegand door access module

Tuesday, September 25th, 2012

A few years ago now I was implanted with an EM4102 compatible RFID tag in my left hand and since then I have created quite a few projects based on reading the tag for various tasks – Mostly access control.  One of my more recent projects was to create a ‘Door access module’ but this one would be different.  In the past I have interfaced with an ID-12 chip from innovations which has a generic serial output. While this is easy to interface with, the readers are expensive and somewhat awkward to use as far as mounting, waterproofing and tamper proofing.

This inspired me to come up with a way of interfacing to industry standard readers.  These readers use the Wiegand data format which comes from the days of mag/swipe cards but it also means this project can be used with almost any Wiegand reader.

This means I can use generic, cheap readers from ebay that generally cost less than $10 coupled with a $20 arduino and a homebrew shield for about $40 total cost. This is about the cost of the ID-12 chip alone.

Initially this project was a very simple reader with grant/deny access and nothing more but I reworked it a bit later on to be a complete online version as well (with Arduino ethernet module and POE).  For now lets look at the basic version.

This simply works by programming in a set of tags to EEPROM and when a card is read it is compared to those in EEPROM and if one matches, access is granted, if not, access denied.  No advanced control is used.  This is handy in scenarios where all users are trusted and you have no care for the time that they get ‘access’.

I made a simple shield that interfaces to the reader via a pin header, a couple of buttons, an output for the strike and a BD681 darlington transistor to handle activating an electronic strike or whatever other high current device you desire.

Downloads: Sketch and Shield in Sprint Layout format