The best solution is not to run from the motor supply. Find an old 12V adapter and run from that. If the board were to draw 100mA (I'm not sure what it actually draws, probably less than that) then the regulator needs to dissipate 3.5W or so at 40V drive. That is way too much. If you put in an external resistor, you just move the problem to another component - there is still 3.5 W that needs to go somewhere. |