Down Stepping 12V to .8V

Are you trying to step down the voltage from a car battery or something else? In any case, there are plenty of IC chips/voltage reducers you can buy at Radio Shack or other electronics components places. Most kits come with a circuit diagram. I would suggest you get or build one that has a variable voltage with a voltate gauge,that way you can use it for more than one experiment. I've done this many many years ago when I first learnt about zener diodes, transistors etc. It sure was much fun.