not Ray here …
not sure which hw version you are running, but if you provide 5V regulated,
would the easiest is to remove Fuse F2 and Feed 5V into TP3 base on the schematic below … or which ever one that match your hw ?
https://github.com/rayshobby/opensprinkler/blob/master/OpenSprinkler%20Pi/hardware/ospi_v13_sch.png
Anh