Increasing voltage from 5 (or 20) to 24.

You will need a boost voltage converter- typically, this is an oscillator and inductor, diode and capacitor, and a regulator to smooth it out. Switchmode power supplies can do this. But be aware that if you boost 5 volts to 24 volts, whatever current your motor draws will also be multiplied by about 5 times plus losses. What that means is if your motor draws an amp at 24 volts, the switching supply will draw about 5 amps at 5 volts.

Cheers!

Chip Shults My robotics, space and CGI web page -

That will do. I suspect 12V would probably be enough to step the motor (at reduced torque etc).