I am using this board to learn how to multiplex properly on the software side.
I am in the process of building a clock using 7 Segment Nixie tubes. Hence the 25V requirement.
http://www.tube-tester.com/sites/nixie/dat_arch/IV-11_2.pdf
I started off using BCD 7 Seg drivers which was fine, but I would like to be able to control the segments from the code to display patterns etc.
So I decided to learn how to multiplex properly first, but with my end goal in mind which is why I had transistors everywhere.
Dean