[sdiy] power supply reverse polarity protection

[Grant Richter]

John Blacet has the best solution I have seen. A combination of heavy
reverse polarity diodes and self resetting poly fuses.

See: Protecting modules from Power Supply Problems

http://www.blacet.com/tech.html

> A thing that is more threatening is wrong polarity.
> It may happen during construction , on the work bench
> or with self made lab equipment (banana plugs)
> that power supplies are swapped to the wrong.
>