Up till now, I've had to use a second computer to talk to the relay box that controls the railway, because the USB - RS232 converters I had crashed the Raspberry Pi. Today, I put the new USB relay card on the job. So now I don't need the second computer. One lonely Pi runs the web site, and the webcam that you see the railway with, and it also talks to the relay board over USB, and that controls the power and switches the train on and off.
Next, I need to move the other functions done by that second computer (email stuff and some email processing) on to the PI (which I've mostly done already) and I can power the tower off permanently.
A USB to PS/2 keyboard converter arrived today. Up till now, I've been using flimsy USB keyboards for the Pies, with no real feel to them. What I really like, are the old IBM model M keyboards that are big and heavy, and make a very satisfying click when you type on them. You can get them now for around £50 (compared to £5 for a cheap plastic keyboard that I'm not enjoying typing on).
A few years back, I bought half a dozen genuine IBM "buckling spring" keyboards, because I didn't ever want to be without one. And now I want to use one of them with a Raspberry Pi.
So when the converter arrived, I opened up the packaging, and saw that the USB connector was big and fat and wouldn't fit on the Pi, not if I also wanted a mouse. However, a USB extension cable soon sorted that out, and now I can type on a model M on the Raspberry Pi.