What I'm making (warning - it's totally useless, but cool) is a digital display that will show me the factor of the speed of light that I'm going. So, if I was going, say, 80mph, the meter would display "0.0000001192c". I think it'll be cool when I finish it. A link to a rudimentary, incomplete page:
http://www.igglybob.com/projects/sol_meter/ I need the -5VDC for the analog to digital converter I am using (the ICL7135). It says I can get away without it, but no matter how I try I'm not able to get it working without that -5VDC.
The second poster on the link you gave brings up an interesting point, but I'm not sure it can work. I would explain why, but I'd be diving into theory that I'm not 100% sure of at the moment and that's always a bad idea.
The easiest solution, of course, is if I can find myself a negative voltage source, but I'm not sure one exists.
Thanks for the help!