My UNO switches off

When I power up my UNO it immediately powers down again. The pilot light at the USB socket glows momentarily then turns off.

I have a feeling this is bad news, but what is this telling me?

A solution might be to re-burn the bootloader, but from what I understand it doesn't stay on so i assume you can't connect it to the IDE. If its the standard UNO and not a SMD variant you can try to change the chip or try to burn the bootloader on it with another arduino. I have no experience with this so I don't know how this exactly works, but its worth trying since your arduino is probably dead at the moment :(

noelvissers: since your arduino is probably dead at the moment :(

I changed the UNO - same result. First UNO works fine with another sketch. Don't think it's the UNO that's the problem.

NOTE: if I disconnect the power to the circuitry and chips the problem does not occur. The pilot light stays on. It looks like a problem with my circuitry.

Question now is, what sort of circuit problem would cause the UNO to switch off?

A short circuit? A high load even ;)

I had one of my 74HC595 shift registers in the wrong way round. :confused: I shudder to consider what mayhem that may have created. :disappointed_relieved: