I am looking at creating a stand-alone device that will sit between a switch and a few PCs. My goal is to handle multiple 1000BASE-T port disconnects on a timer. Instead of unplugging a cable from the patch panel or doing a port shutdown via a switch command like a sane person, I want the ports to be disconnected by this device.
I have found single cable A/B switch/cutoffs that are physical, but nothing solid state. I was browsing sparkfun recently looking at Arduino projects to try out and saw some relay/timer guides and thought of this idea. I know you are scratching your head because this is redundant but I want to give it a shot as I will be going into a few areas that I have little/no skills currently.
While my electronics knowledge is beyond the average dummy, I am 100% a beginner in this space. My experience normally includes retro/arcade repair type things, (burning EEPROMS, replacing caps, fixing traces, etc.) I want to try making something from scratch and try PCB design, etc. I built a CNC and figured I’d try routing a PCB design out if suitable for this project.
Here is where I am at:
The actual timer/trigger:
This will be the easy part and is more in line with the sort of stuff I normally play with. I have an Arduino Nano and am currently working on the code for a simple countdown timer and LCD output. At zero, the Arduino will either stop triggering a pin to cut power to the ICs handling the Ethernet via a relay, or to trigger the SEL pin if I go with an Ethernet switching IC. I think no matter what the solution is configuration will be similar.
Actually handling the network traffic without destroying the signal:
I am aware that there are complexities handling 1000BASE-T on a PCB, and see there are many guidelines to follow if you don’t want to cause signal degradation, cross talk, etc. I have found half a dozen manuals/guides on the subject and am currently reading through best practices for PCB design regarding Ethernet. Im sure Ethernet on PCB is common enough of a task that I can gather enough data to make good choices. (I am certainly open to input though)
That said, the part where I am struggling the most is on deciding what components can handle these signals without degradation AND be able to stop them on demand.
After a few hours browsing through several TI and MAXIM products, I have a few ideas, but they don’t feel right.
The first component I considered basing the design on is a MAXIM MAX4890E 1000 Base-T LAN Switch. I started reading up and my thought was to route the Ethernet in and then only connect one of the outputs. I would then use the SEL pin to switch to the connected output pins when I want the port to be up. I am now reading into it further and if I am understanding correctly I would need to use Ethernet Transformers on both sides of each chip so it could handle the signals. In trying to keep cost semi- reasonable (I will probably have 8 ports or so), and coupled with wanting the traces as short as possible for signal quality, this solution seems flawed.
I later started looking into signal conditioners and redrivers. I found some TI chips that seemed to be promising, however just slapping 8 of these in again seems less than ideal. I have looked at several different ICs like CB3Q3245 and SN74CB3T3245 as I just need to cut off the connection. I see skew/bandwidth limitations on most devices that I would think may impede the signal. I feel like I am either over complicating this idea or reading too deep into some way to do is in a more simple manor.
Someone please tell me how off course I am! Thanks!