What This Is
This project is for a small electronic unit that allows the user to sense the presence and relative signal strength of wireless hotspots. It can be worn as a pendant or carried in a pocket. It is “always on” and communicates the presence and signal strength of an in-range hotspot by way of sequences of pulses – like a heartbeat you can feel. The stronger and faster the “heartbeat”, the stronger the wireless signal detected.
It does not actually authenticate or otherwise interact with a hotspot in any way. It is a 100% passive device, meaning it transmits nothing — it can detect hotspots, but cannot be detected itself.
How It Was Made
This project consists of a microcontroller, some custom interface electronics, a small vibe motor, and an off-the-shelf Wi-Fi detector – the one I used is by D-Link and is keychain-sized.
Here is the sensor I used, and some pictures of the construction. Details of the design will follow.
How It Works
The microcontroller periodically “presses” the button on the detector to initiate a reading. Then the microcontroller “reads” the output from the indicator LEDs on the detector, and uses this as the basis for pulsing out a signal on the vibe motor, which the wearer can feel.
In this way, the unit keeps you updated on the presence and signal strength of a wireless hotspot in your vicinity. No pulses means no signal. Short pulses means a weak signal. Faster, more frequent pulses means a stronger signal. This feedback is very much like a heartbeat, and is extremely intuitive to interpret.
How To Make Your Own
First of all, I use a microcontroller in this project. If you aren’t familiar with terms like 12F629 or .HEX files and how to blast them into a PIC, you will have trouble with this project.
Read more: Build your own Wireless Network detector using PIC12F629