15 Feb
2006
15 Feb
'06
5:23 p.m.
I'm guessing so. Am wondering if the 1.67 amp 24 vdc
regulated wall warts from BGMicro are sufficient to
power an 8" floppy drive (NEC FD1165-A). Needs 24 vdc
@ 18 watts. Would love to devise a circuit to get the
5 vdc (@ 5 watts) off the same brick, but that may be
asking too much ;).
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17 Feb
17 Feb
12:14 a.m.
On 2/15/2006 at 5:23 PM Chris M wrote:
I'm guessing so. Am wondering if the 1.67 amp 24
vdc
regulated wall warts from BGMicro are sufficient to
power an 8" floppy drive (NEC FD1165-A). Needs 24 vdc
@ 18 watts. Would love to devise a circuit to get the
5 vdc (@ 5 watts) off the same brick, but that may be
asking too much ;).
One of mine doesn't--just uses a transformer with 2 secondaries and a small
rectifier/filter/regulator PC tucked into the case in about 2" of speace
behind the drive. Works fine on a Qume DT-8. That 24vdc supply you
mention should do just fine, but the 5vdc draw may be heavier than you
think, particularly if you have the standard 220/330 terminators installed.
Cheers,
Chuck
2:46 p.m.
behind the drive. Works fine on a Qume DT-8. That
24vdc supply you
mention should do just fine, but the 5vdc draw may be heavier than you
think, particularly if you have the standard 220/330 terminators installed.
I've yet to see a floppy drive that used 220/330 ohm terminators. Every
one I've worked on just has a 150 ohm resistor to the +5V line. It'll
still draw the current if that line is pulled low, though.
-tony
4:39 p.m.
On 2/17/2006 at 10:46 PM ard at p850ug1.demon.co.uk wrote:
I've yet to see a floppy drive that used 220/330
ohm terminators. Every
one I've worked on just has a 150 ohm resistor to the +5V line. It'll
still draw the current if that line is pulled low, though.
You're right--I was thinking of MFM hard drives. But the approximately 4V
dropped through the 150ohms x 8 input signal lines is still about 200 ma, a
signficant current. I note that on the 8" drive specs that I have, max 5v
current is about 150% of typical, so one needs to make sure which number is
being used.
In any case, I'd probably over-design a PSU for one of these rather than
use one that just meets it.
Cheers,
Chuck
3:27 a.m.
In article <20060216012335.87648.qmail at web61020.mail.yahoo.com> you write:
I'm guessing so. Am wondering if the 1.67 amp 24
vdc
regulated wall warts from BGMicro are sufficient to
power an 8" floppy drive (NEC FD1165-A). Needs 24 vdc
@ 18 watts. Would love to devise a circuit to get the
5 vdc (@ 5 watts) off the same brick, but that may be
asking too much ;).
24v 18W is .75 A, well within the stated specs.
5v 5W is 1A, so a liniar regulator would overload the wart, besides
needing to dissipate 19W.
A switching regulator should have no problem doing the 24v to 5v 1A
conversion. http://romanblack.com/smps.htm has some lower current
examples.
--
Blars Blarson blarson at blars.org
http://www.blars.org/blars.html
With Microsoft, failure is not an option. It is a standard feature.
1:25 p.m.
Basically:
1.67 Amps X 24 Volts = 40 Watts. (I*E=P)
40 Watts - 18 Watts = 22 Watts of remaining capacity.
You need 5 Volts at 5 Watts, which is the same as 5 Volts at 1 Amp. A
series pass regulator delivering 5 Volts at 1 Amp from a 24 volt source
will waste 19 Watts of heat. (24V - 5V = 19V; 19V X 1 Amp = 19 Watts)
19 Watts + 5 Watts = 24 Watts required. Not Quite enough!
Your rated power requirements may be absolute maximums. Your drive may
actually use less than rated, so it *could* work, but a separate supply
would be best.
-Bryan
Chris M wrote:
I'm guessing so. Am wondering if the 1.67 amp 24
vdc
regulated wall warts from BGMicro are sufficient to
power an 8" floppy drive (NEC FD1165-A). Needs 24 vdc
@ 18 watts. Would love to devise a circuit to get the
5 vdc (@ 5 watts) off the same brick, but that may be
asking too much ;).
2:34 p.m.
I'm guessing so. Am wondering if the 1.67 amp 24 vdc
Nothing _needs_ a switch-mode PSU. All a disk drive needs is the right
voltages, at sufficient current, and with low ripple/noise.
I've been working on an Epson drive recently, and have been using an
RS-branded drive exerciser. The manual for that says that swtiching
supplies might put noise on the supply lines, and that it's often easier
to see the alignment patterns if you use a linear supply.
There have been plenty of disk drive units that use linear supplies.
regulated wall warts from BGMicro are sufficient to
power an 8" floppy drive (NEC FD1165-A). Needs 24 vdc
@ 18 watts. Would love to devise a circuit to get the
5 vdc (@ 5 watts) off the same brick, but that may be
asking too much ;).
24V at 18W is 0.75A. 5V at 5W is 1A. Since your PSU can only supply a
total of 1.67A, less than the sum of those 2 currents, you would need to
design a switching regulator for the 5V supply. A linear regulator cannot
give out more current than it draws from the input supply.
One other thing to be wary of. Those power ratings might be the average
power when in operation. Many drives take a much higher peak current to
start the spindle motor (an 8" drive might have a mains motor, though) or
load the head, or... You do not want the supply to drop momentarily when
this hapepns, it will cause all sorts of problems. Personally (based on
too many problems with wall warts), I'd design the whole PSU from scratch.
-tony
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