I am a very novice chiphacker and am asking for ideas on how I might implement something like this.
I am about to start an RFID project, which is the easy part. RFID readers are cheap, arduinos are cheap, and RFID tags are cheap.
But I want the ability to turn the RFID tag "on" or "off". I want to be able to say "when this happens, then allow yourself to be 'excited'".
The project I'm working on is testing for the presence of a liquid (which has ions in it.) So one high-level solution would be "separate the RFID chip from its antenna. When the liquid is spilled, it 'shorts' that connection and now the tag may be excited."
So my question is this: first, is there any mechanism for turning a tag "on"? There are plenty of ways to turn them "off" (basically destroy the tag) but nothing that works in the opposite direction. And how farfetched is the "liquid" idea?
Might there be some resource that could help me understand what possible workarounds would be, or different attributes of different kinds of RFID tags? Or even something that tells me why this won't work?