Electronics > Electronics

Contact sensor with identification exchange?

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dlynch13:
Capacitive sense is an interesting idea.  I thought that it could only detect humans?  I am going to experiment with that idea and see if I can detect the difference between my other bots versus other objects.  I really just need to know that I hit another bot, then I can use the timestamps to see which one I hit.  But I still wonder if other inert objects might "look" like my bot.

jwatte:
Here's an idea:

Each bot is covered in wire (cage, fur, mesh, etc) that carries a signal, which is at first approximation a square wave at some particular frequency. This uses capacitive coupling both for signal generation, and for signal sensing.

Each bot has its own particular frequency, where the difference in frequency between any two bots is at least 1 kHz to allow for short contacts (a few milliseconds) to be discriminated. This means carrier frequency must be in hundreds-of-kilohertz up to megahertz range -- approximately the radio AM band range of frequencies.

Each bot analyzes the signal it actually sees on the contact shroud for beating frequencies, which are generated when some other frequency is present in addition to the specific bot's emitted frequency.

This will tell you if there is a contact, and what the ID of that other bot is.

Right before the men in black from the FCC breaks down your door for operating an unlicensed radio transmitter :-)

johnwarfin:

--- Quote from: dlynch13 on October 05, 2013, 10:37:20 PM ---Capacitive sense is an interesting idea.  I thought that it could only detect humans?

...

I still wonder if other inert objects might "look" like my bot.
--- End quote ---

actually metal objects work better than humans. its the water in people that conducts but metal does that a lot better. if tuned sensitive enough it can trigger up to an inch or two away but for my "tuna-bot" (chicken-of-the-sea frame) actual contact was required at the charging station. once this occured bi-directional communication was a cinch. very reliable even if electrodes corroded and noisy due to the nature of the capacitive link.

of course each bot needs unique id stored in ee so we can tell who is who.

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