Raspberry Pi
Rpi-3 Test Bench (Rpi-4) Infrastructure Environment Server
Rpi Info

I started playing with Raspberry pis (rpi) a couple of years ago and have put some to decent use.   I've found that the Rpi-3 is a good platform to run Ubuntu headless server, and Rpi-4 runs full Ubuntu desktop OK.  

Rpi-3

I run a headless server on the Rpi-3s because the 3 doesn't quite have enough resources to run X very well.   By running Ubuntu on the Rpis I can always "talk" to them via ssh.

My electronics bench with an Rpi-3 running Ubuntu 20.04 Server on the work top.  



A little closer look at the desktop.   I really like this portable keyboard and monitor, they make it easy to see whats running on those rare occassions when I need to look at an Rpi without removing it from it's assigned duty.



Close look at the Rpi-3.   Note the USB plug, its the bluetooth interface for the keyboard/mouse.



Environment Server

The Environment Server actually runs on an Arduino Nano, but it is accessable to everything on my network via an Rpi-3 running Ubuntu 20.04 headless server and my infrastructure.   The systems in my woodshop communicate with RS232, the Shop Gateway allows everything on my network talk to them or anything else I might add.  

This is the Rpi-3 running Ubuntu headless server with the shop gateway software under my infrastructure.   Note it has a sheld or hat, and on the shield is a CYT1070 level translater from 3V to 5v for Rs232 talking to an Arduino Nano.   I've had some thoughts about letting it communicate with the Automated Dust Collectors in my shop.



Bottom of the shield, showing the RPIO connector.   I left the pins long enough so it would mate with the Rpi-3's GPIO connector inside it's plastic case.
BTW: this same shield fits both Rpi-3B+ and Rpi-4B+.  



Top of the shield showing the connector for the level translator.  



Shop gateway mounted on the door frame in the shop.  



The Rpi-3 talking to the Nano while testing.  



Test Bench (Rpi-4)

My electronics test bench, you can see it's Rpi-4 attached to the inside, upper left of the hutch.   It's monitor is on the left extension and it's keyboard mouse is on the keyboard pull-out.
I have realized I can take the Rpi-4, folding monitor, and portable kbd as a traveling computer.   I also have an Amazon Fire Hd 10+ with keyboard which travels well.



Closer look at the Rpi-4 on the test bench.