Drive logic/motor power supply

All you really need is one power supply at +12V DC. Then add a +5V regulator to the rails of the +12V DC. As long as you add a surge protection diode to the inputs of the motor, anode to ground, cathode to +, your pretty much safe.

Reread your question, it seems you WANT to use two different power supplys. Even though this isnt the best way, actually the wrong way (if you are not using a PSU, which provides the reg +5v already), Your not going to mess up anything, it should work perfectly fine. But as I said before there is no need for 2 different supplys. If you add a +5V Regulator to the +12V Line, the motor will still get +12V and the Logic gates will still get a regulated +5V. Regulator only need sub mA currents, so the amount of current you can use is still "virtually" the same.

I'd prefer using a single supply, really, but the main part of the project uses a 9v AC adapter (which I can't change), which of course gets stepped to 5v for its own logic, so I thought for simplicity's sake, I'd just borrow the 5v from that for the logic of the drive, and then use a separate AC adapter to run the drive motor directly. A more final design might warrant a nicer setup using a regulator and power switch mounted on a pcb (or better yet, the ability to turn itself off when it detects the main part of the project is off), but as just a hobbyist, I thought I'd see what was possible with the fewest parts first.

Using a compact flash to IDE adapter was also a thought, since it only needs 5v throughout, and if it's a decent CF card, it'd support 8-bit mode, saving me some of the glue logic to convert normal IDE to 8-bit.

In any case, thanks for clearing that up!

I thought I might also ask, what would the best amount of amps be to run disk drive motors? Would 12v at 1 amp do it fine? Or could it manage with fewer amps? Or possibly it needs even more than 1 to function adequately?

I found specs online somewhere a few months back. Some of the newer drives use 5 VDC at a low current IIRC.

DC Power Supply 5 V DC Power Consumption Operating(typ) Seeking 3.90 W Reading 1.60 W Writing 1.55 W Standard(typ) 0.04 W

So it looks like 5 VDC at 800 mA max.

You might also want to look at some hard drives for laptops. If I recall correctly, some of them only need low voltage, (5 or maybe less) and they are definately optimized for low current.

They need 5 volt, and will refuse to work if that is a few tenth of a volt lower. That might also be the reason why some of them do not like to work in an usb controller, with shaky contacts and high wire resistance. If you can choose, use 5.2 volts.

how much 5V and how much 12V is written on the drive.

In the future some drives will be using 3.3v too. (that or the orange wire on SATA connectors is just for show)

new ones typically want less than 1A of 5V and of 12V