door opener science project

Posted on Feb 4, 2014

This button, with a few hacks, now makes it so we can open up our office with our Nexus Ones, iPhones or even SMS. Located near the reception desk, this button opens an electronic latch on the front door. Pulling the assembly out of the wall revealed the system to be about as simple as possible: the button simply connects two wires. Bridging them with a screwdriver fired

door opener science project
Click here to download the full size of the above Circuit.

the latch (from their small gauge and uninsulated connections, it was obvious we weren`t dealing with dangerous voltages, but please don`t start pulling cable from your walls unless you know what you`re doing). Connecting two low-voltage wires electronically isn`t a particularly hard trick, so I decided it`d be fun to spend some evenings building a system to expose that switch to our network. I`ve built a few projects in the past that make use of custom router firmwares and Arduino microcontrollers, so I decided to use those tools for the job. I`m a big fan of this approach - it`s a great, inexpensive way to add a scriptable network interface to your microcontroller projects (if you`re interested, I talk more about this technique here ). Ultimately, I ran into difficulty getting this particular router`s serial connection to work, so I abandoned the Arduino - it was overkill anyway. Inspired by the excellent new MAKE: Electronics book, I decided to build a circuit to do the job. Here`s the finished franken-router, hooked up to the switch: So how does this all work Well, let`s start with the router. It`s a Linksys WRT54GL, a still-Linux-friendly descendant of the WRT54G, the router which jump-started the custom firmware scene. There are a lot of custom router firmwares available - DD-WRT, Tomato, Gargoyle - and they can all make your consumer-grade router do some professional-grade things. For this project I used OpenWRT,...

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