[Nate True] states several times that there isn’t any good use for this project, but his wireless motion sensor is still fun. The transmitter features a passive infrared motion sensor. It sends the output over the 433MHz band to the receiver module. The receiver has a small piezo that plays sounds based on the PIR’s output. His project is featured The Bleeding Edge 006.
[Refik Hadzialic] has updated is site with a how-to that could be rolled into many different projects. Using a receiver and transmitter pair from Laipac he demonstrates how to communicate wirelessly between two microcontrollers. The pair costs about $12 and operates at 315MHz. He’s got a chunk of commented code in the article to give you an idea of how it works.
1-Wire is a low speed communications bus. OWFS is the 1-wire filesystem for Linux. Combine the two with a WRT54G and you’ve got a cheap wired/wireless network enabled data collection platform. 1-Wire devices are really low cost, only need one wire plus ground, are bus powered, and can even be wired in a branching pattern instead of a normal straight run. OWFS lets you check the status of the devices like they were parts of your filesystem (it’s built on FUSE). So, you can do really easy data collection just by writing some file management scripts.
This is a really simple way to measure WiFi strength. Actually, it will measure anything in the 2.4Ghz range, like your microwave. The device consists of a two element quad antenna, a Ghz sensitive diode and a variable capacitor for tuning. The sensor is plugged into a voltmeter for measurement. The page has links for locating the specialized diodes.
[h. p. friedrichs] (AC7ZL) has some great plans for building a crystal radio. The stator coil and output coil are wrapped around the outside of a CDR sleeve. The tuning capacitor is constructed by sandwich two clear CDs between metal and attaching this inside the top of the sleeve. The rotor shaft is mounted using the bushings from a pair of disassembled potentiometers. A hot needle is used to tap the stator coil through the housing every fifth turn. Even though the parts aren’t very traditional it looks like a really solid radio. He’s got instructions for building a matching ear piece out of tea tins too.
Reader [Krome] wanted a reliable, modular, weather proof WiFi bridge. The outer weather box was purchased for $50. The main radio is a proprietary Wi-Lan HP45-24. A lightning arrestor is included because this proprietary box was purchased before the WiFi band was official allocated and would be hard to replace. A Linksys WRT54G is used as the local access point and is connected to a Hyperlink 500mW amplifier. The Wi-Lan box and the amplifier have their antennas connected to panel connectors on the outside of the box. The WRT and Wi-Lan box are both powered by an ATX power supply while the amp is connected to the pass-through. Looks like a really solid setup and it should be easy to replace individual components if they fail.
Wondering how to get the best performance out of your homebrew WiFi antennae? This homebuilt SWR meter will help you measure and match the impedance of your antennae with your source. A good match will ensure maximum power transfer. Use the full schematics or you can just buy the meter from the site.
