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I would like to power a floppy drive without using a PSU out of a computer, and power it off something like batteries or a bench power supply, I know that the red wire is 5v and the black is ground and the yellow wire are 12v, however I want to know why there are two different power inputs the red and yellow wires.

I think there are 2 different power inputs as they control different things Ie the yellow (12v) controls the stepper motor inside and the 5v the floppy drive read head but I am not sure on this and would like some on to help clarify

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  • Basically it is just like you said.
    – arminb
    Commented Nov 17, 2016 at 15:48
  • Thanks for the help, i want to make a musical floppy drive and was seeing if i could use just 12 volts to power it making my life easier as i only have to step the mother and not actually read anything from the disks
    – TheMelonKing
    Commented Nov 17, 2016 at 15:51
  • I am not sure about that. The yellow wire provides the reference voltage for the stepper motor. I don't think it's a control wire. The controlling takes place in some chip inside the floppy hardware.
    – arminb
    Commented Nov 17, 2016 at 15:54
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    What size floppy drive are you referring to?
    – fixer1234
    Commented Nov 17, 2016 at 18:11
  • FYI - floppy drives have two motors: one for the R/W head, and another for the spindle. On 8" floppy drives, the spindle motor required AC line power. "power inputs as they control different things" -- No, power simply provides power (i.e. electrical energy), there's no "control" through power. Besides it's DC voltage, meaning it doesn't change. How can something that doesn't change control something else? @arminb - The floppy drive is just a transport device for the diskette. The floppy controller is external to the drive.
    – sawdust
    Commented Nov 17, 2016 at 21:06

3 Answers 3

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The 12V power is not used in 3.5" floppy drives for the last 25 years (I assume the question is about 3.5" formfactor). Everything is powered from +5V wire. The 12V is not used, it goes nowhere. That's why floppy drives fit USB enclosures, where only 5V is available.

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Yellow +12v does power the stepper motor. Red +5 does power logic+electronics. Since you will be using logical signals (5v logic levels) from an external floppy controller chip to control the floppy's stepper motor, both logic and stepper supplies are required - you need both +5v and +12v. And don't forget the two black ground wires - they are connected together inside the floppy drive.

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  • 2
    This information about 12V is at least 25-years old. All 3.5" floppy drives use +5V solely, the 12V on standard power connector simply not used.
    – Ale..chenski
    Commented Nov 17, 2016 at 17:58
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yellow (12v) controls the stepper motor inside and the 5v the floppy drive read head

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    Why are you answering your own question with incorrect information?
    – sawdust
    Commented Nov 17, 2016 at 21:10

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