Hackaday member CNLohr has created some stunning images of a Wi-Fi network using a remarkably simple technique. He documented his experiments on his Hackaday project page.
He achieved the results by capturing wireless signal strength using a Wi-Fi chipset hooked up to a single multi-color LED. The LED rapidly changes color depending on signal strength. He then captures long-exposure photographs of the LED, as his buddy, holding the piece of kit, moves around a space. The result is a multi-colored graphic with variations representing signal strength.
Pinging the chipset
This simple, but apparently effective, signal strength measurement is created by pinging the chipset from a PC. Software on the PC then looks at the receive power and sends a unique color command to the Wi-Fi module, which delivers it to the LED.
The changing LED colors indicate the relative changing of signal strength. In other words, wherever you wave the chipset-connected LED, the LED's color indicates the receiver power at that point in the space.
Hence the graphic. Blue indicates powerful signals and green represents areas where signal is less powerful.
Tools used include a four-dollar, quarter coin-sized ESP8266 Serial-to-Wi-Fi module. The ESP8266 is a self-contained Wi-Fi networking device with TCP/IP and an on-board processor that allows it to host applications.
It's also a good choice, by the way, for those wishing to experiment with the Internet of Things. You might be able to run a web server on it, if you can figure it out.
Lohr provides power to the kit with a 1S mini-drone lithium-polymer battery at 3.7V. He uses a Hubsan battery, but I'm sure any 1S lipo would work just fine.
The video below provides a full run-down of the experiment, including further details on the kit.
CNC milling images
The second phase of his experiment includes using a computer-mapped CNC Mill, a tool ordinarily used to create machined parts. He attaches the Wi-Fi module and uses a zigzag grid pattern. This grid-mapping, where the scans occurs uniformly, allowed him to create an in-depth 3D image.
In the CNC experiment, he recorded the position of the mill, along with the Wi-Fi strength to create the data. He then uses gaming non-euclidean ray-tracing graphics software to create the 3D image, which he exports to a browser. You can see the final animated result here.
Other mapping tools
Lohr's system isn't the only tool out there if you're interested in not-spot mapping your Wi-Fi network. Some off-the-shelf solutions can do the trick too, although they're mostly limited to 2D images.
How-To Geek explains how to create a heat map using a free copy of Ekahau HeatMapper. The Windows-based software works best if you can import a blueprint of your space—like an architectural drawing of an office.
And I've used Farproc's Wi-Fi Analyzer for Android, which I think is one of the best analyzers, because you can download the app on a smartphone and walk around with it easily.
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