OWL - One Wire Lock

Introduction

This page describes a project that started out as a way to use iButtons to open and close a garage door. The project is much more than an iButton garage door opener. It is really an iButton keyed switch (i.e. electronic lock). Since that doesn't lead to a catchy acronym, the project is instead called One Wire Lock, which has the catchy acronym OWL.

The hardware/software configuration described here is rather limited because it only supports one relatively local lock (i.e. keyed switch).  If multiple locks (or one less local lock) need to be supported, it would be more appropriate to use a DS2409 at each lock, but that would be a different project altogether.  For simple situations where only one relatively local lock is required or running lots of 1-Wire (i.e. twisted pair) cabling is undesireable, this project is very useful.

WARNING: This page is in the early stages of development!!

Hardware

All of the hardware gets mounted directly on the Rev A Socket board and the socket board still fits into a Eurocard enclosure.

Complete Component List

• 1 Rev D TINI (software requires on-board DS2433 for key storage)
• 1 Rev A Socket Board w/o parallel I/O circuitry (Rev C should also work)
• 1 PNP transistor with 2 built-in 10 kOhm biasing resistors (NTE2356)
• 1 5VDC Normally Open Reed Relay (Radio Shack Cat. No. 275-232)
• 1 Diode (1N914, though similar diodes would be suitable)
• 1 Pair of screw terminals (taken from STEP+ board)
• 1 iButton receptor (I used a Blue-Dot receptor for prototyping)
• Some 30 gauge wire wrap wire
• Some 22 gauge solid hook-up wire

Schematic

• The schematic of the OWL hardware added to the TINI Socket Board

Images of Working Prototype

The links below will take you to images of an actual modified (and working) Rev A Socket Board. Be sure click on the "Detail" link for a close-up view of the added hardware. These images were made by placing the Socket Board directly on the scanner glass. Due to the tall capacitor on the top of the Socket Board, the images of the top of the board are not so good because the board itself was farther from the scanner glass. (See how many cold solder joints you can find!)

• The bottom of the modified Rev A Socket Board (Detail)
• The top of the modified Rev A Socket Board (with TINI removed) (Detail)
• The edge of the modified Rev A Socket Board (with TINI installed) (Detail)

Software

The software works well, but only uses the 1-Wire address of the iButton to determine whether the "key" is valid.  If stronger or more versatile security were required, the software could be reworked to use SHA-1 buttons which could contain, in addition to the 64 bit secret, things like hours during which the "key" is valid, etc.

Downloadable software coming soon...