Building A Mesh Networked Conference Badge

[Andrew] just finished his write-up describing electronic conference badges that he built for a free South African security conference (part1, part2). The end platform shown above is based on an ATMega328, a Nokia 5110 LCD, a 433MHz AM/OOK TX/RX module, a few LEDs and buttons.

The badges form a mesh network to send messages. This allows conversations between different attendees to be tracked. Final cost was the main constraint during this adventure, which is why these particular components were chosen and bought from eBay & Alibaba.

The first PCB prototypes were CNC milled. Once the PCB milling was complete there was a whole lot of soldering to be done. Luckily enough [Andrew]’s friends joined in to solder the 77 final boards. He also did a great job at documenting the protocol he setup, which was verified using the open source tool Maltego. Click past the break to see two videos of the system in action.

11 thoughts on “Building A Mesh Networked Conference Badge

  1. I think there’s some confusion with the word “open source” and developer features like Maltego Scripting Language. You still have to pay almost $1000 USD to get setup but they allow you to do your own scripting. I know that’s not the true sense of open source.

    OK I do not get what HaD is doing here. I think we would like to see this thing in operation at the South African Security conference. How about some backgrounding? How did someone present the author with a problem and how did he solve it? Mesh networking is quite intriguing as it does present some interesting solutions to message propagation. But please explain how that is accomplished with this application.

    Is it infrared, radio, what? How does the user MAKE a message? Does (s)he type it, speak it, or select canned messages from a menu? What is the learning curve for an end-user? I see a bunch of confusing button presses but have no idea what’s happening. Why would a conference goer use this when (s)he could just as easy use their cell phone to send SMS messages to others?

    It sounds like it could be a revolutionary idea for SMS on a larger scale but this HaD leaves me needing more information. Did you patent it yet?

    1. Hey,

      Actually you can just grab the free community edition of Maltego (but it has some limitations) from the website.

      The way it all works is covered in the blog post, but the TL;DR version:

      All badges transmit their badge number as well as relationships they know about other badges pick up those transmissions and send them on around the network and the main PC picks them up to display all the relationships on the screen.

      End user doesnt need to do anything (menu system provides other functionality), the idea was just that you could track and visualise user-to-user interactions to see how people were interacting at the conference, as seen in these pics: (testing) (at conference)


      1. Fascinating…

        Curious… I see that the geographic relational positions are displayed on main PC screen. Is this an actual geographic position or just conceptual? If it is actual geographic, how does the badge “know” what it’s geo-position is in the building? Using mesh network would mean that there are no 433 MHz satellite transceivers (repeaters) in the ceilings as each badge serves as it’s own satellite transceiver (so to speak).

        If the main PC is using some sort of automatic radio direction finding (RDF), how does it get a proper parallax fix to be able to do the needed trigonometry for azimuth and distance? If it’s time domain distance measures, then how do you get azimuth?

        If it’s all just conceptual then I guess my question is moot.

        1. Ha, no these badges worked at the conference, so there was no conceptualness to them :)

          The badges do not track positions but only interactions, so that graph really just shows people who were close enough together that their badges sync’d up (most likely that they were talking).


          1. That’s what I meant by “conceptual”. I know your badges worked and did so very well too. I was just wondering if the PC screen was showing TRUE geographic location in the building or not. You answered my question – they are not.

            Have you thought of this idea?: I was reading an article about a system that linked people of like mind together using a badge type of idea. I believe it was called GAYDAR. Of course it’s not important that it was only meant for gay people. It was a shame that no one thought to evolve the idea away from sexual-preference to a more socio-collaborative idea.

            Ideally I envisioned using such a gadget to enter in your likes, dislikes, hobbies, bio-info, and desire to connect with a like individual. It would work great at seminars and conferences as you could filter out the boring types and focus only on the people that pique your interests (and vice versa).

            It would buzz, beep, or flash when someone you’d like to meet is near you by a few feet. It would transmit your bio-data, description, and photo image to them and theirs to you. You could set up filters that would filter out any unwanted social connections. It could even have a QR code or a URL code labeled on it to allow someone to go to your more detailed webpage (or bio-page) using their cell phone camera or just typing in the URL code on their browser screen.

            Here’s an idea for geolocation service. Make some badges that are only for marking a grid coordinate in a building. Station them at that grid coordinate plugged into AC power. They could just hang out of the wall outlet. Their RF transmitter is set to a power to limit range drastically and prevent overlap. They would not need a receiver. They only transmit the grid coordinate over and over like a beacon to any badge that’s nearby. Any of your badges pick up the signal and record that the badge is or was near that beacon. If the signal is low enough you could pinpoint someone’s present or past location by a few feet.

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