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Drive logic/motor power supply

F

FyberOptic

Hiya, I was considering adding either a floppy and/or hard drive into a
project I'm working on, and since either requires 12v to run the
motors, I got to wondering about something. Are the logic and motor
components of such a drive totally isolated from one another? I mean,
if I want to power the logic board of a drive from the power source of
the project itself, but I want to power the motor from an independent
external source, is this possible without frying the other side? One
would think this would be the case, but I thought it's best to confirm
before I start sticking things together!
 
M

Mr. J D

FyberOptic said:
Hiya, I was considering adding either a floppy and/or hard drive into a
project I'm working on, and since either requires 12v to run the
motors, I got to wondering about something. Are the logic and motor
components of such a drive totally isolated from one another? I mean,
if I want to power the logic board of a drive from the power source of
the project itself, but I want to power the motor from an independent
external source, is this possible without frying the other side? One
would think this would be the case, but I thought it's best to confirm
before I start sticking things together!

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.
 
M

Mr. J D

FyberOptic said:
Hiya, I was considering adding either a floppy and/or hard drive into a
project I'm working on, and since either requires 12v to run the
motors, I got to wondering about something. Are the logic and motor
components of such a drive totally isolated from one another? I mean,
if I want to power the logic board of a drive from the power source of
the project itself, but I want to power the motor from an independent
external source, is this possible without frying the other side? One
would think this would be the case, but I thought it's best to confirm
before I start sticking things together!

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.
 
F

FyberOptic

Mr. J D said:
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!
 
F

FyberOptic

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?
 
H

Homer J Simpson

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

http://www.mitsumi.com/products/floppyspec.html

So it looks like 5 VDC at 800 mA max.
 
M

Martin

FyberOptic said:
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!

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.
 
S

Sjouke Burry

Martin said:
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.
 
J

jasen

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?

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
 
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