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'[EE]: Paralell port powered little device.'
2000\06\05@132545 by Edson Brusque

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Hello,

   I'm doing a little device to be attached to the paralell output of a PC.
I want to take the power to the device (5V, about 40mA max) from the
paralell port.

   I'm looking at some datas and it says the four control pins are
open-collector. This means I cannot take +5V from it... :(

   Anyone have already made something like this? How can I do that?

   Best regards,

   Brusque

2000\06\05@133210 by Tim Hamel

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Brusque,

I do not think you'll be able to suck that much current from the parallel
port without frying it. The max you'll get from maybe the data pins is (I
think, don't quote me on this) 1-2mA per pin. The newer port controller chips
often have IEEE-1284 Level 2 outputs, which can source 12 milliamps at 2.5V,
so maybe you can use a step-up chip?

Regards,

Tim Hamel

In a message dated 6/5/00 10:26:25 AM Pacific Daylight Time,
spam_OUTbrusqueTakeThisOuTspamFLYNET.COM.BR writes:

> Hello,
>
>      I'm doing a little device to be attached to the paralell output of a
PC.
{Quote hidden}

2000\06\05@134217 by Dan Michaels

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Brusque wrote:
>Hello,
>
>    I'm doing a little device to be attached to the paralell output of a PC.
>I want to take the power to the device (5V, about 40mA max) from the
>paralell port.
>
>    I'm looking at some datas and it says the four control pins are
>open-collector. This means I cannot take +5V from it... :(
>
>    Anyone have already made something like this? How can I do that?
>

40 mA, good luck!! Drawing more than a couple of mA off an
Rs-232 or parallel port is usually more than can be hoped for.
Especially if you want the thing to work off more than just
the computer you initially used.

Open-collector means it "sinks" power, does not source it. It
wants/needs "your" juice.

Sometimes, however, you can get away with wiring several "source"
lines of the **same** voltage in parallel, with each connected thru
a small [eg, 10 ohm] resistor, for some minimal isolation. MAybe can
get a few mA from each, adding up to something usable.

- Dan Michaels
==============

2000\06\05@140912 by Arthur Brown

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Why not take the power from the keyboard conecter or a games port
40Ma from the printerPort is not easy to do, as some motherboards use open
collecter outputs if you reduce your Ma request you could take a small
voltage from unused datapins at the lower ttl high voltage.
Art
{Original Message removed}

2000\06\05@184523 by Bob Ammerman

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Dongles manage to scrape up a usable amount of current out of a parallel
port!

My handy-dandy PC tech ref identifies pin 35 on a standard 36 pin centronic
printer cable as +5V via 3K3 ohms. This pin does not appear on the DB25 at
the PC end though.

Bob Ammerman
RAm Systems
(high performance, high function, low-level software)

2000\06\05@190218 by Edson Brusque

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Hello all,

Arthur Brown wrote:
>Why not take the power from the keyboard conecter or a games port
>40Ma from the printerPort is not easy to do, as some motherboards use open
>collecter outputs if you reduce your Ma request you could take a small
>voltage from unused datapins at the lower ttl high voltage.

   Take power from the keyboard connector seens to be the option. I could
make an adapter using a pair of din connectors and take the signals from pin
4 (GND) and pin 5 (+5VDC/VCC) to power my little gadget. What about using a
pair of resistors (say, 47R)in series with the GND and VCC to limit the
current in case of short-circuit?

   Best regards,

   Brusque

2000\06\05@195846 by Mark Willis

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I have seen more than one Parallel Port card modified such that the DB25
connector's pin 18 is re-defined as +5V (even one re-wired to have +12V
on there IIRC.)  IF you do that, document it WELL, hang a notice tag off
the card and off the printer cable, and still expect to some day have
problems (Fuse the +V line going into DB25 pin 18, ok?)

Try to cut down from 40mA, definitely, if you want to power off the
parallel port.  And check for patents on this (I know one local company
(?IQ Technologies?) had patented this same trick on Serial Ports.)  I'd
bet Parallel Technologies might have a patent here, if IQ Tech doesn't?
(Worked with both places somewhat.)  Not a problem for personal
non-profit use, though.  (It's been a while since then!)

Tricks here:  Have your PC-based code intentionally drive all of these
data lines high, as much as possible.  Siphon power off each of these
pins with a Schottky.  Cap right off those to supply power to the
device.  Obviously you have to do this intelligently...

With 8 pins, you can probably get ~4.6V while drawing 16-20 mA (as an
estimated upper limit.)  Use a plug-in Parallel Port card for this in
case you blow the card up.  Obviously, your protocol has to have room in
it for some of the data lines to be pulled up most of the time from the
PC side - Think "Pull all 8 lines high when in Idle state."  If you can
get by with less current, obviously you only need to pull the lines you
have diodes on, high.

Earlier PC ParPort's Data Out pins: 74LS374 octal latch, sources 2.6 mA
MAX, damaged if pulled low too hard.  Don't want to use a 10,000uF cap
on the other side of those Schottky's, 1uF or so is about it IIRC.  (it
HAS been a while.)

 2   D0          Data Bit 0
 3   D1          Data Bit 1
 4   D2          Data Bit 2
 5   D3          Data Bit 3
 6   D4          Data Bit 4
 7   D5          Data Bit 5
 8   D6          Data Bit 6
 9   D7          Data Bit 7

You cannot do too much with these, as they're OC Outputs (7405's
originally.)
 1  /STROBE      Strobe
14  /AUTOFD      Autofeed
16  /INIT        Initialize
17  /SELIN       Select In

I'll second Arthur's idea - Joystick port will source quite a lot of
current (Ahem, it's NOT fused inside the PC, usually, and the smell of
smoking ribbon cable's NOT very nice, so be careful you wire it right.)

Keyboard port's also do-able (I'm about to put a laptop on my tech
bench, with an adapter inline with the keyboard cable.)  Buy a
polyswitch to replace the (usually 2A) keyboard picofuse WHEN you blow
it, ask if I can help you fix your laptop.  And I can find those fuses
if you cannot <G>

For information:
http://home.rmi.net/~hisys/parport.html
http://www.senet.com.au/~cpeacock/  has MOVED to
http://www.beyondlogic.org/ - that's Craig Peacock's pages, GOOD info,
take a look as it's better IMO than before
http://ftp.sunet.se/hwb/ for pinouts on most everything else, BTW <G>

 Mark

Edson Brusque wrote:
{Quote hidden}

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

2000\06\05@203020 by Mark Willis

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Edson Brusque wrote:
> Hello all,
>
> Arthur Brown wrote:
> >Why not take the power from the keyboard conecter or a games port
> >40Ma from the printerPort is not easy to do, as some motherboards use open
> >collecter outputs if you reduce your Ma request you could take a small
> >voltage from unused datapins at the lower ttl high voltage.
>
>     Take power from the keyboard connector seens to be the option. I could
> make an adapter using a pair of din connectors and take the signals from pin
> 4 (GND) and pin 5 (+5VDC/VCC) to power my little gadget. What about using a
> pair of resistors (say, 47R)in series with the GND and VCC to limit the
> current in case of short-circuit?
>
>     Best regards,
>
>     Brusque

Why 2 resistors?  And why 47R (1.88V drop at 40mA - Apiece!)

I'd suggest perhaps 10R instead, 0.4V drop at 40mA, but then your Isc is
0.5A and your keyboard fuse probably will be safe.

 Mark

2000\06\05@204932 by Bob Ammerman

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----- Original Message -----
From: Mark Willis <.....mwillisKILLspamspam@spam@FOXINTERNET.NET>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Monday, June 05, 2000 8:28 PM
Subject: Re: [EE]: Paralell port powered little device.


> Edson Brusque wrote:
> > Hello all,
> >
> > Arthur Brown wrote:
> > >Why not take the power from the keyboard conecter or a games port
> > >40Ma from the printerPort is not easy to do, as some motherboards use
open
> > >collecter outputs if you reduce your Ma request you could take a small
> > >voltage from unused datapins at the lower ttl high voltage.
> >
> >     Take power from the keyboard connector seens to be the option. I
could
> > make an adapter using a pair of din connectors and take the signals from
pin
> > 4 (GND) and pin 5 (+5VDC/VCC) to power my little gadget. What about
using a
{Quote hidden}

Of course, at 0.5A, your 10R resistor will end up dissipating 2.5W, which is
quite enough to turn a 1/4W (and probably even a 1/2W) resistor into a fuse!
You might be better off with an actual low-current fuse or polyswitch
device.

Bob Ammerman
RAm Systems
(high performance, high function, low-level software)
[And occasionally a little (digital) hardware :-) ]


>   Mark

2000\06\05@211456 by Dale Botkin

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On Mon, 5 Jun 2000, Edson Brusque wrote:

>     Take power from the keyboard connector seens to be the option. I could
> make an adapter using a pair of din connectors and take the signals from pin
> 4 (GND) and pin 5 (+5VDC/VCC) to power my little gadget. What about using a
> pair of resistors (say, 47R)in series with the GND and VCC to limit the
> current in case of short-circuit?

You definitely do want to limit the current.  Most system boards have a
picofuse on the keyboard Vcc line.  If you draw too much, you blow the
fuse -- which results in what appears to the consumer as a dead
motherboard.  Not a nice thing for anyone concerned.  Yeah, a techie can
find & replace the fuse, but not Joe Average.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

2000\06\05@213411 by rottosen
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I have posted an example of a minimal PIC circuit I built a long time
ago that draws a fraction of a milliamp from the parallel port.

See   http://www.idcomm.com/personal/ottosen/  under the Stupid PIC
Tricks heading for the "Printer Tester".

Good luck getting more than a milliamp or so. Designing the circuit for
operation using a low voltage version of the PIC and other circuits
should help some though.

-- Rich



Dan Michaels wrote:
{Quote hidden}

2000\06\05@222045 by William Chops Westfield

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Nowdays, you could consider getting power from the USB ports, I think...

BillW

2000\06\05@223521 by Bob Ammerman

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USB guarantees 100ma on each port!

(500ma for 'high power devices, but you need a real USB device to request
the power and not all environments actually support the higher power).

Bob Ammerman
RAm Systems
(high performance, high function, low level software)


----- Original Message -----
From: William Chops Westfield <.....billwKILLspamspam.....CISCO.COM>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Monday, June 05, 2000 10:18 PM
Subject: Re: [EE]: Paralell port powered little device.


> Nowdays, you could consider getting power from the USB ports, I think...
>
> BillW

2000\06\06@121732 by Harold M Hallikainen

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       Has anyone seen these keyboard power splitters available commercially?
I've seen them packaged with some products, but have not seen them on
their own. Also, the ones I've seen have been for the old "big DIN"
connector, not the new "little DIN". Do they exist for the little DIN?
Finally, you can use a PTC thermistor for overcurrent protection without
getting as much voltage drop as with the suggested resistor.

Harold



On Mon, 5 Jun 2000 19:29:36 -0300 Edson Brusque <brusquespamspam_OUTFLYNET.COM.BR>
writes:
{Quote hidden}

FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

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2000\06\07@043759 by Tom Handley

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  Mark, PC parallel port DB-25 pin 18 is pretty much `the' standard GND.
I've seen pin 25 used for power but, like you said, I'd document it, send
up a flare, and put on a flashing red-light... What I do (when not using
a wall wart), is get the power from the Keyboard. The typical power budget
has room to spare and it's easy to make an in-line connector to bring out
the power. One issue is how close the Keyboard GND is to the Parallel GND
on the motherboard.

  - Tom

At 04:58 PM 6/5/00 -0700, Mark Willis wrote:
{Quote hidden}

PC.
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

2000\06\07@060529 by Michael Rigby-Jones

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I have also been looking for these with no success.  The best type have a
PS2 plug at one end and a din socket at the other and are supplied with a
PS2/Din converter.  By plugging this on one end or the other of the power
splitter you can use iether PS2 or Din keyboards.  Easy enough to make
someting in small quantities, but a PITA for anything higher.

Mike

> {Original Message removed}

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