Wednesday, February 2, 2011

A simple electronic lock using an iButton

My friend Bob (PICMAN), started this project a while ago (way before 1995 I think), he did lots of commercial applications with iButtons, and now he is a member (Senior Member and a leader) of our international freelancer group.

You can do lots of things with iButtons, from electronic door locks to security systems, this tutorial will show you how to make a simple but very useful iButton application for electronic locks.

Components required:
  • Door strike
  • PIC Microcontroller
  • 7 segment LED display
  • Power transistor
  • 5v regulator
  • Momentary switch
  • iButton reader
  • iButtons type DS1990A
  • 12v source



The PIC has the number of the iButton master programmed into the EEPROM.

When the master iButton is touched against the iButton reader the PIC goes into a routine waiting for a user iButton(s) to be touched against the reader.
When this iButtons is touched it is allocated a number 0 to 9 which appears on the 7 segment led display and the iButtons number is also written to the PIC’s EEPROM.
The user iButton when touched against the reader will now activate the door strike for 5 seconds.
The process can be repeated for another 9 user iButtons.

To deactivate a lost iButton, touch the master iButton against the reader, and push the switch a number of times until the number of the lost iButton appears on the 7 segment display, then touch the master iButton against the reader.

The hex file of the software and circuit diagram can be acquired by me, Ligeti:, please write iButton in the subject of the Email.

We also have a limited number of the iButtons and readers for sale.

A more secure system can be constructed by using an iButtons with memory such as the DS1992L.


 Please feel free to comment, and ask questions if you have any.

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