In that case, a job very well done!
I'm an experienced electronics tinkerer, but my projects (even simple ones) take days to finish; 1 hr. thinking about a problem & how to solve, 5 minutes implementing the solution :-)
You're right, Hugh's solution is simple, and I've seriously considered building this design. However, the LED-issue (which is very easy to solve, BTW: unsolder one lead of each LED, and insert a resistor of about 1k (1000 ohm) in series; this limits current to normal levels) has made me wonder about other design flaws that I don't see yet. (am not an electronics engineer, just an experienced hobbyist).
There are plenty of schematics around of these kinds of regulators, also using MOSFets for dumping the load; I will have a look in my directories to see if I can find any that are easy to build, and will link to them here. Advantage of MOSFets over relays is reliability (relay contacts can/will burn out, bounce, etc.), while MOSFets are fully electronic components. Also, a MOSFet is easier to mount (even when it needs cooling) than a relay, IMO.
About reversing ICs; it happens to all of us. TIP: use an IC-socket, this way replacing one becomes a piece of cake. Remember one spectacular failure of a NE555 (timer IC) years ago, that I plugged in backwards: it projected parts of its black case straight into my face! (ever since, I wear glasses when working on electronics or soldering). After the even, you could see the bare silicium chip...
All in all, a job well done. (back at engineering school, we used to say that constructions engineerings (architects) were just those that couldn't cut it at mechanical engineering ;-) ). Or: mech.engineers make weapons, constructions engineers/architects make targets :-p
Peter,
The Netherlands.