I agree for the unconstant voltage of the alternator. That was why I was talking about filter which would act as regulator in this case.
If the ST needs more than 1A for its 5V, I will use a power transistor (TIP32 for example) upon the LM7805 to drive additionnal current from an other way than it. And with appropriated thermal discipators everything will be ok.
Don't worry I won't forget to add some fuses to preserve my ST if I do that one day. I am used to build power supply. I have done a 230V AC to [-12V +12V] 2A DC some years ago.
