In the past I damaged some components connected my PC by using the USB power for a 5V source when I connected a device backwards, so I built this circuit out of spare parts left over from other projects.
My goals which I succeeded at was:
1) Protect the USB power source from reverse voltage
2) Prevent the device connected to the output terminals from experiencing reverse voltage
3) Have at least 4.9V at the output terminals
4) Have a 1A fuse to prevent the circuit from pulling more than 1A in the case of an overload or short circuit
5) Not spend any money, only use parts I already have
My goals I did not succeed at was:
1) Protect the USB power source from short circuit of the 5V output terminals
2) Drain any left over power in the circuit once disconnected (as it is, once I disconnect the USB power input, if there is nothing on the output connection, there is still about 2.2v in the circuit)
I verified that if I connect a device expecting 5V in reverse to the output terminals, the USB power source is safe, and the BLUE LED becomes dimmer. If i measured the output test points, voltage drops to about 3.3V while a device is connected in reverse.
I am very happy that it is working this far, but I still want to solve the goals I did not succeed at (protect from short circuit at the output, and add a resistor to drain the leftover power)
What should I modify about my circuit to meet the goals I did not succeed at? How would you change the circuit to make it simpler & more effective?
Thanks for your help.
(Edited at 11:22PM PST: Realized i made a mistake on the schematic; fixed now)