Has anyone got any experience using multiple fathom X interfaces on a single tether?
I am aware this is theoretically possible, but wondered if anyone had practical experience. If not I will do some experiments.
Our use case is for a cave diving project with submerged habitats. where we would like to place multiple IP cameras at different distances into a flooded cave. Horizontally roughly 25 m, 50 m and 120 m. We are trying to minimise the number of cables for safety reasons, so would like just to run a single ethernet or even a slim ethernet with minimum twisted pairs.
All help and comments much appreciated, and I will feedback as I build a system.
Hi @JonD
Welcome to the forums!
I’ve had success with multiple Fathom-X modules sharing the same twisted pair - connecting two cameras to the same box, but using 3x Fathom-X. “Daisy-chaining” the two wires with the modules also works.
For your case, with not very noisy power draw, you could run both signal and power over the same two wires! You could use standard fathom tether and combine all 8 wires, running positive voltage on 4x and ground on the other 4, while also connecting these lines to the green Fathom-X +/- terminals. In each housing, you would convert the voltage to power the Fathom-X and camera if necessary, and be able to connect the ethernet directly. The slim tether may not have enough copper to carry the power required, depending on what voltage you supply. This calculator can help!
Those distances should be fine, but there is a limit in bandwidth. Overall, you likely won’t be able to exceed 60-80 Mbps… That should be fine for just a few cameras though!
Thanks for that, it has given me plenty of inspiration!
We actually run quite a lot of copper into the cave already as we have a surface supplied heating system for divers decompressing. We run 4 cores in two pairs at 36v (14AWG/2mm^2 each) to avoid line losses and then drop it down to 12v in each habitat.
You have now made me realize we can probably use these existing cables for the data. Though I am also interested in getting other sensors into the habitats so may go to the trouble of running an ethernet or tether cable.