Thanks for the explanation of the project! I did something similar 15 or
20 years ago. This was strobe lights for motorcycles. I don't remember
what the regulator for the PIC was, but I used an LM317 as a current
regulator off the raw +12V. It connected to the anode of each LED series
string. I used high power white LEDs designed for camera flash. I think I
had four in series in each string. At the bottom of each string was an FET
driven by the PIC. The PIC sequenced the LED strings. The pulse width was
reduced for night use, reducing the apparent brightness. I MAY have used
another LM317 t regulate the +12V down to 5V to reduce the variety of
parts. Since the PIC was only driving FET gates, the power consumption
(and the regulator dissipation) was very low.

There are concerns about voltage spikes due to load dump in automotive
applications. There are some regulators designed especially to handle
this, but a series R and a transient voltage suppressor may be cheaper. If
the 5V power consumption is high, a switching regulator would be
appropriate. There are some inexpensive modules from muRata and others
that are drop in replacements for an LM7805. I think the muRata one can
take more than 32V input.

Good luck!

Harold



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