Yesterday I saw
this post and smiled. There is nothing that makes me happier than knowing that a buck saved some student a couple hundred dollars of grief.
We evaluated every single power input connection for protecting against reversed inputs, and added it only where it made sense. In general, high power devices are quadratically more expensive to protect than low power devices. By expensive, I don't just mean raw dollars: I also include power loss
and safety.
For example, the PD only reverse protects its power supplies, and does not protect the normal breaker outputs. The power supplies are ~50 Watts reasonable peak with mild pulse, and it cost a dollar. The entire robot is 2ish kiloWatts reasonable peak (with painfully higher pulse), and would have cost 40 dollars of FETs plus a heat sink plus a fan plus a significant drop in total robot performance.
There are two types of reverse input protection: Pass and Crowbar.
Pass solutions are things like series diodes or series FETs that have to handle (pass) the normal operating current. The control system components in blue plastic all use pass protection.
Crowbars are things like shunt diodes that short out the power input in an attempt to blow an upstream fuse before exploding. These make me nervous: It is a protection against incorrect wiring that assumes that the rest of the robot is correctly wired. In particularly badly wired robots, they can make the situation worse. I typically use crowbar protection in more controlled environments.