Post by thread:[EE]: Paralell port powered little device.

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

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 ==============

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

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

----- Original Message ----- From: Mark Willis <.....mwillisKILLspam@spam@FOXINTERNET.NET> To: <PICLISTKILLspamMITVMA.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}> > 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. 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

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

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}> > 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 > ==============

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 <brusquespam_OUTFLYNET.COM.BR> writes: {Quote hidden}> 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 FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: dl.http://www.juno.com/get/tagj.

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}>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: >> Hello, >> >> I'm doing a little device to be attached to the paralell output of a PC. {Quote hidden}>> 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 ------------------------------------------------------------------------ Tom Handley New Age Communications Since '75 before "New Age" and no one around here is waiting for UFOs ;-)