First grab some fact´s that we need to know about a Floppy Drive.
As Sample I took a NEC FD1231H drive cause it is very often to get on Ebay or Second Hand Shop´s. information’s can be found here.
NEC only give us 5/12V and 1/4W as comments. So we need around 300mA on 5V or 125mA for 12V. There is no advice about the used Voltage… Does it needs 12V or just 5V or both? NEC says it requier´s min 5V.
The big Question is, das USB gives us enought current?
USB 1.X ~ 100mA max.
USB 2.X ~ 500mA max.
USB 3.X ~ 900mA max.
We need 2 external PCB´s, a Arduino Mini-Pro and a FTDI232 or a generic interface to get the Data from the Floppy. The Pro Mini takes around 200mA max. The FTDI max rating´s are 24mA. But what about the Floppy if it´s in bad shape?
So best way is to use an external Power Supply 12V and 1A to be on the secure side.
You can order a PCB for few bug´s soon on ALLPCB.COM , you can plug and play put your hardware at home on the PCB and just need to connect the Floppy to it
A Bundle PCB with all needed part´s except the Floppy and Power Supply, can purchased soon. A Privat to Privat sale and not Commercial. Same for other PCB´s that you can get here too.