The Raspberry Pie (Raspi) is a credit card sized $30 computer. It has an ARM processor, digital screen output, USB interface for keyboard and mouse and other peripherals, an Ethernet port, and it runs Linux from an SD card. 

It also has an I/O port that can be directly connected to switches and LEDs, although if you get a connection wrong you can blow your Raspi. There are add on boards that can isolate the the connections and drive higher currents.

So why am I mentioning this in a model railway blog? I have a couple of Raspi’s but have not done much with them yet. I am always thinking of ways of using them in model railways. I notice that there are several signal levers available now with in built switches and with my interest in signalling may come up with an interlocking program, but that may take some time.

It has occurred to me that I could just use one to drive multiple LEDs on my diorama. At first it may seem OTT to use a computer more powerful than a BBC micro to drive a few LEDs, but with lights in multiple rooms a very realistic pattern of switching on and off could be achieved. Also, software could be used to create fire or arc welding effects. Connecting a light sensor to detect darkness would be easy.

The Raspi is so cheap that it can be used in distributed applications where several talk to one another to achieve an objective. They can also be run off a battery, but the Ethernet port consumes a great deal of current, so if you don’t need networking and want to run off a battery, use the model A which lacks this port.