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Apple 5.25 disk drive current requirements? [message #388628] Mon, 11 November 2019 01:43 Go to next message
Anonymous
Karma:
Originally posted by: awanderin

Does anyone know how much current Apple 5.25" disk drives use on their
+5V, +12V, and -12V rails? If so, I would like to know.

--
Jerry awanderin at gmail dot com
Re: Apple 5.25 disk drive current requirements? [message #388631 is a reply to message #388628] Mon, 11 November 2019 03:07 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: James Davis

On Sunday, November 10, 2019 at 10:43:42 PM UTC-8, awanderin wrote:
> Does anyone know how much current Apple 5.25" disk drives use on their
> +5V, +12V, and -12V rails? If so, I would like to know.
>
> --
> Jerry awanderin at gmail dot com

IIRC, I saw it once, somewhere, but I don't remember where. Some ideas:

Have you looked in the Apple II Technical Notes for Disk II info?

Based on the limits for the Apple II power supply, the wire size/gage (AWG), it can't be much more than 500 milliamps, total. There are schematics, but do they show current draw?

Has anyone ever seen a Disk II Technical Reference Manual? Is there such a thing?
Re: Apple 5.25 disk drive current requirements? [message #388664 is a reply to message #388631] Mon, 11 November 2019 20:41 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
James Davis <JPD.Enterprises@outlook.com> wrote:
> On Sunday, November 10, 2019 at 10:43:42 PM UTC-8, awanderin wrote:
>> Does anyone know how much current Apple 5.25" disk drives use on their
>> +5V, +12V, and -12V rails? If so, I would like to know.
>>
>> --
>> Jerry awanderin at gmail dot com
>
> IIRC, I saw it once, somewhere, but I don't remember where. Some ideas:
>
> Have you looked in the Apple II Technical Notes for Disk II info?
>
> Based on the limits for the Apple II power supply, the wire size/gage
> (AWG), it can't be much more than 500 milliamps, total. There are
> schematics, but do they show current draw?
>
> Has anyone ever seen a Disk II Technical Reference Manual? Is there such a thing?
>

The +12v current will depend on both the design of the drive and its
rotational friction, which will also depend on the characteristics of the
diskette inserted.

The other currents should be much less variable, though +5v will be
affected by the design of the analog card.

Maximum permissible currents are specified by slot specs, but they are
frequently ignored by card designers. However, the Disk ][ Controller is
specifically designed (by Woz) to minimize idle power consumption.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Apple 5.25 disk drive current requirements? [message #388669 is a reply to message #388664] Tue, 12 November 2019 02:15 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: awanderin

Michael J. Mahon <mjmahon@aol.com> writes:

> James Davis <JPD.Enterprises@outlook.com> wrote:
>> On Sunday, November 10, 2019 at 10:43:42 PM UTC-8, awanderin wrote:
>>> Does anyone know how much current Apple 5.25" disk drives use on their
>>> +5V, +12V, and -12V rails? If so, I would like to know.
>>>
>>> --
>>> Jerry awanderin at gmail dot com
>>
>> IIRC, I saw it once, somewhere, but I don't remember where. Some ideas:
>>
>> Have you looked in the Apple II Technical Notes for Disk II info?
>>
>> Based on the limits for the Apple II power supply, the wire size/gage
>> (AWG), it can't be much more than 500 milliamps, total. There are
>> schematics, but do they show current draw?
>>
>> Has anyone ever seen a Disk II Technical Reference Manual? Is there
>> such a thing?
>>
>
> The +12v current will depend on both the design of the drive and its
> rotational friction, which will also depend on the characteristics of the
> diskette inserted.
>
> The other currents should be much less variable, though +5v will be
> affected by the design of the analog card.
>
> Maximum permissible currents are specified by slot specs, but they are
> frequently ignored by card designers. However, the Disk ][ Controller is
> specifically designed (by Woz) to minimize idle power consumption.

Thanks for this.

What I want to do is control an Apple II disk drive from outside an
Apple II, and so my power supply needs to be able to supply at least
enough current for the three power rails. The Apple II Ref Manual (1979
version) says the power supply provides:

[page 92]
+5V: 2.5 A
-5V: 250 mA
+12V: 1.5 A (2.5A intermittent)
-12V: 250 mA

[page 104] says a 48K Apple II and no peripheral cards draws:
+5V: 1.5 A leaving 1.0 A for peripheral cards
-5V: 0 mA 250 mA
+12V: 400 mA 1.1 A
-12V: 12.5 mA 237.5 mA

[page 107-108] state the current available for all peripheral cards:
SUPPLY divide by 8 and you get
+5V: 500 mA 62.5 mA
-5V: 200 mA 25.0 mA
+12V: 250 mA 31.2 mA
-12V: 200 mA 25.0 mA

I've looked in the tech notes but I didn't find it.

My hunch is that the Disk II system uses more +12V current than this
when the drive is spinning. I suppose I could take a look at the motor
part numbers and see if I can find data sheets on them in order to find
out their current draw.



--
--
Jerry awanderin at gmail dot com
Re: Apple 5.25 disk drive current requirements? [message #388670 is a reply to message #388664] Tue, 12 November 2019 02:19 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: awanderin

Michael J. Mahon <mjmahon@aol.com> writes:

> James Davis <JPD.Enterprises@outlook.com> wrote:
>> On Sunday, November 10, 2019 at 10:43:42 PM UTC-8, awanderin wrote:
>>> Does anyone know how much current Apple 5.25" disk drives use on their
>>> +5V, +12V, and -12V rails? If so, I would like to know.
>>>
>>> --
>>> Jerry awanderin at gmail dot com
>>
>> IIRC, I saw it once, somewhere, but I don't remember where. Some ideas:
>>
>> Have you looked in the Apple II Technical Notes for Disk II info?
>>
>> Based on the limits for the Apple II power supply, the wire size/gage
>> (AWG), it can't be much more than 500 milliamps, total. There are
>> schematics, but do they show current draw?
>>
>> Has anyone ever seen a Disk II Technical Reference Manual? Is there
>> such a thing?
>>
>
> The +12v current will depend on both the design of the drive and its
> rotational friction, which will also depend on the characteristics of the
> diskette inserted.
>
> The other currents should be much less variable, though +5v will be
> affected by the design of the analog card.
>
> Maximum permissible currents are specified by slot specs, but they are
> frequently ignored by card designers. However, the Disk ][ Controller is
> specifically designed (by Woz) to minimize idle power consumption.

Found this document on archive.org that has a graph of the 12V load and
it goes north of 2 A when the motor starts:

https://archive.org/details/Apple_IIc_External_Disk-1983-03- 09

--
Jerry awanderin at gmail dot com
Re: Apple 5.25 disk drive current requirements? [message #388673 is a reply to message #388670] Tue, 12 November 2019 04:06 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: James Davis

Most motors draw their highest current when first turned on, starting; some are designed to prevent it. Until a motor gets up to speed, there is less counter electromotive force to reduce its current draw. The higher the current, the higher the torque, the faster it starts. That is why it is always best to start a multispeed motor, like an oscillating 3-speed house fan, with oscillating and high speed switched in first, before you turn it on; it starts up fastest. If you do it the opposite way, and the fan is old and has sticky bearings, it may not start at all; it just heats up until it catches fire.

If you go by the maximums for an Apple II power supply, you should have enough capacity to run a couple of Disk II FDD's. You could use one of those replacement power supply kits that Reactive Micro (?) sells to power up your FDD's separately from an Apple II.

I suppose you could get one of those break-out boards for testing ribbon cables to test the currents with a multimeter, if you really want to know the specifics for the FDD's you are going to use.
Re: Apple 5.25 disk drive current requirements? [message #388684 is a reply to message #388673] Tue, 12 November 2019 10:24 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Ernie Soffronoff

This discussion reminds me of something I heard in the 80s that maybe someone can confirm or deny. Back then I heard there was some proto-malware that could fry your Apple II by turning on multiple floppy motors at the same time. Neither I nor anyone I knew back then had more than two Drive IIs and supposedly that wasn't enough to overload the power supply, but for people who ran big BBSes with lots of floppy drives it could theoretically work.

Anyone else remember this legend? Any truth to it?

--Ernie
Re: Apple 5.25 disk drive current requirements? [message #388691 is a reply to message #388628] Tue, 12 November 2019 11:15 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Frank M.

The Applesauce controller returns the following values, which seem typical for all drives I've tried. I'm assuming the motor and stepper are on the 12v rail, and only the logic ICs are on 5v (Idle).


Power Consumption in Amps:

Idle: 0.09
Motor: 0.23
PH0: 0.30
PH1: 0.25
PH2: 0.25
PH3: 0.31

f
Re: Apple 5.25 disk drive current requirements? [message #388714 is a reply to message #388670] Tue, 12 November 2019 14:32 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
awanderin <awanderin@gmail.com> wrote:
> Michael J. Mahon <mjmahon@aol.com> writes:
>
>> James Davis <JPD.Enterprises@outlook.com> wrote:
>>> On Sunday, November 10, 2019 at 10:43:42 PM UTC-8, awanderin wrote:
>>>> Does anyone know how much current Apple 5.25" disk drives use on their
>>>> +5V, +12V, and -12V rails? If so, I would like to know.
>>>>
>>>> --
>>>> Jerry awanderin at gmail dot com
>>>
>>> IIRC, I saw it once, somewhere, but I don't remember where. Some ideas:
>>>
>>> Have you looked in the Apple II Technical Notes for Disk II info?
>>>
>>> Based on the limits for the Apple II power supply, the wire size/gage
>>> (AWG), it can't be much more than 500 milliamps, total. There are
>>> schematics, but do they show current draw?
>>>
>>> Has anyone ever seen a Disk II Technical Reference Manual? Is there
>>> such a thing?
>>>
>>
>> The +12v current will depend on both the design of the drive and its
>> rotational friction, which will also depend on the characteristics of the
>> diskette inserted.
>>
>> The other currents should be much less variable, though +5v will be
>> affected by the design of the analog card.
>>
>> Maximum permissible currents are specified by slot specs, but they are
>> frequently ignored by card designers. However, the Disk ][ Controller is
>> specifically designed (by Woz) to minimize idle power consumption.
>
> Found this document on archive.org that has a graph of the 12V load and
> it goes north of 2 A when the motor starts:
>
> https://archive.org/details/Apple_IIc_External_Disk-1983-03- 09
>
> --
> Jerry awanderin at gmail dot com
>

Exactly—that’s why the 2.5A intermittent rating on the +12v line.
Essentially all of the drive load on +12v is the drive motor, whose running
current is a strong function of the turning friction of the diskette.

You’ll find that the load on the negative supplies is minimal, +12 is as
described above, and +5 is just the TTL logic on the analog card, probably
around 100mA.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Apple 5.25 disk drive current requirements? [message #388718 is a reply to message #388684] Tue, 12 November 2019 16:12 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: awanderin

Ernie Soffronoff <ernie.s@gmail.com> writes:

> This discussion reminds me of something I heard in the 80s that maybe
> someone can confirm or deny. Back then I heard there was some
> proto-malware that could fry your Apple II by turning on multiple
> floppy motors at the same time. Neither I nor anyone I knew back then
> had more than two Drive IIs and supposedly that wasn't enough to
> overload the power supply, but for people who ran big BBSes with lots
> of floppy drives it could theoretically work.
>
> Anyone else remember this legend? Any truth to it?

If you have multiple controller cards, it is possible.


--
Jerry awanderin at gmail dot com
Re: Apple 5.25 disk drive current requirements? [message #388719 is a reply to message #388691] Tue, 12 November 2019 16:14 Go to previous message
Anonymous
Karma:
Originally posted by: awanderin

"Frank M." <frank_o_rama@hotmail.com> writes:

> The Applesauce controller returns the following values, which seem
> typical for all drives I've tried. I'm assuming the motor and stepper
> are on the 12v rail, and only the logic ICs are on 5v (Idle).
>
>
> Power Consumption in Amps:
>
> Idle: 0.09
> Motor: 0.23
> PH0: 0.30
> PH1: 0.25
> PH2: 0.25
> PH3: 0.31

Thanks Frank, that is really helpful!

--
--
Jerry awanderin at gmail dot com
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