Hi – I’m working on developing a GPS / LoRa tracker for Diamondback Terrapins (DBT) with some colleagues. DBTs spend a lot of time in brackish water and we’re considering adding a salt water switch to the tracker to limit GPS power consumption but don’t have knowledge about what type of switch to use or how best to add it to the bundle. Any advice or pointers to resources would be appreciated.
The project is still quite young but if anyone is interested in our initial ideas I’m happy to share. Once we have a better idea what the final package will look like I’ll figure out a platform for posting progress with the hope other folks will benefit from our work.
Ned
23 May 2024 2:54am
I'm going to use a TTP223 module as a solution. This is a capacitive touch switch, used to turn things off and on. It's not just human touch that triggers it, anything somewhat conductive and grounded, like a body of water, in close proximity, will set it off. This means it can be placed inside a waterproof enclosure and still be able to detect when the enclosure is submerged. I'll update when I've actually used it in anger.
31 May 2024 5:27pm
Hey Ned,
If you want to add a transmitting component to your tag, let me know. I would happily provide the open-source Argos boards and some free satellite service time.
31 May 2024 6:43pm
Hi, @nedhorning, sounds fascinating! I'm going to listen in to hear how things progress, including with the capacitive sensor described in this thread. That sounds wise as it insulates the electronics.
Also wanted to mention that we use a comparator circuit following a reference design from TI that I can't find at the moment but probably could with more digging if desired. We described its basic design and use in a saltwater switch in this paper (open access) if you want to read a bit more.
Harold Tay