Introduction: Idea Turn an Obsolete PC Into an Electronics Engineering Experimentation Environment

PCs go obsolete at a furious rate. The 4-year old 1GHz PC just isn't adequate to run the latest bloatware, fast action games, video and photo editing, and so on. But it's still fast enough to do SOME stuff, surely. Shucks, the 8-year old 400MHz system show up in the trash and I'm SURE they can run a C compiler or plain text editor just as well as they ever did.

And there is all sorts of minor hardware and sophisticated (but generally free and open source) software that can turn a PC into a useful lab tool.

Step 1: Lab Power Supply

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There are already several instructables on making a bench-top power supply using an obsolete computer supply. There's no reason that you have to take the power supply out of the computer to do this; the average computer has plenty of spare power for a few experiments. And the popular +12 and +5V supplies are on nice convenient connectors (designed to attach to disk drives.) Put a panel with a couple of power jacks in a spare bay and you're golden...

With slightly more effort, you can add some fuses and ammeters, both of which are probably good ideas.

With significantly more effort, you should be able to come up with a variable voltage current-limited supply that still fits in a bay.

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Step 2: Oscilloscope From Sound Card Inputs

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There is assorted software on the net that lets you use the line inputs of your sound card as a crude oscilloscope, though of course it is rather limited in bandwidth capability (About 20kHz vs 20MHz for a low-end "real" scope), and not so easy to calibrate either. Still, there is lots you can do with a 20kHz uncalibrated scope.

With additional effort and $$, you can add a more complex analog front end for better range, isolation, input impedance, etc.

(with SIGNIFICANT $$ and little effort, you can buy a half-scope that connects to the computer via USB and has real scope-like functionality and bandwidth. It'd still be somewhat less than a real scope. (but then we're talking about $$$ where it would make sense to put this in a brand-new computer.))

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Step 3: Function Generator From Sound Card Output

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Likewise, there is existing software to turn the output of a sound card into a function generator, capable of generating sine, triangle, square, and complex waveforms at assorted frequencies.

An additional analog front end would provide greater output range and power drive capability, clipping to digital levels, etc.

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Step 4: Logic Analyzer Using Parallel Port?

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Supposedly you can also get a crude logic analyzer out of the parallel port. I have my doubts whether this would be as useful as the sound-card scope, but you could at least do a multi-line logic analyzer.
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The outputs of the parallel port could also be used for digital signal generation (but without the timebase of the sound card, exact timing might be difficult to get.)

Additional electronics creates more capabilities, up to "real" logic analyzers that connect via USB.

Step 5: Protocol Analyzer Using Serial Port

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Serial data is common enough in projects that one might as well use the serial port to analyze serial data. Also, assorted voltmeters, printers, device programmers, and so on might use the serial port as-is.

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Step 6: Assorted Simulators and Software Tools

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And of course there is lots of existing freeware from vendors.
Switchercad, MPLab, AVR Studio, spice, and many more.

Step 7: Summary

Most of this stuff already exists. What I'd like to see is a page collecting large SETS of them, with instructions and gotchas, all in one place. Maybe even a linux live-boot CD you could insert and get an Instant EE environment (but we need not restrict the tools to running on linux.) (But it would be nice to have full tools sets for MULTIPLE operating systems.)

I'm particularly soliciting recommendations for packages that people have used and found useful, as distinct from half-finished projects that never quite worked....


Sharingan Silk (author)2006-08-16

I'm not sure I'd quilify a 4-year-old 1GHz pc a obsolete. But if you have a pc that is really obsolete, say a good old 486DX or pentium 60/66/75/90..., you can still turn it into a network storage device using naslite. Cram a network card, four 300GB hard drives in it and you have a 1.2 TB network drive for less than 300€ (while a 250GB NAS costs about that much here in France). Of course, it works with a more recent pc but as mentionned above, obsolete is a word only you can define.

or you can buy a few of the 2Tb external hdd and then you have a super computer that never forgets a thing that you put on it... can you ever run out of mem on a 2tb external hdd???

Razanur (author)girrrrrrr22012-05-06

I already run out 2TB. Series are quite effective. If you have them in HD, one file is 2GB, one Series has up to 10 Seasons which has up to 24Episodes each.
Or imagine a photographer who has a good camera with RAW-pics, they can be up to 250mb EACH!

Razanur (author)girrrrrrr22012-05-06

I already run out 2TB. Series are quite effective. If you have them in HD, one file is 2GB, one Series has up to 10 Seasons which has up to 24Episodes each.
Or imagine a photographer who has a good camera with RAW-pics, they can be up to 250mb EACH!

westfw (author)girrrrrrr22007-07-30

Easy; edit video. about 12GB/hour for uncompressed video from miniDV cameras, so the 2TB is only about 150 hours worth. That's a lot of video, but by no means an inconceivable amount. My mac currently has about 200G of video plus still pictures, and I can easily imaging having 10x that amount by the time the kids have all moved out (and that's not even assuming that I'll move to HD video or >8MP jpegs.) Interestingly, one of by early computer-related memories concerns the ARPANet "Terrabyte storage project", circa 1979. DARPA wanted to see what the uses of having "virtually unlimited" online storage would be. So this contractor set up a robotic tape storage faciity; big room with a bunch of tape cartridge drives (2 inch video tape?) and a lot of tapes, to implement the full terrabyte. Relatively random people could get storage space (sorta "if you can access it, you must already have the correct prerequisites." Hmm.) Keep in mind that this was the timeframe when one of those large washing-machine sized 14inch disk drives held about 100MBytes, and the university mainframe hosting 10000+ students would usually have far less than 1GB total storage. So the advent of 1TB drives that you could just go out and buy (and carry home in one hand) was one of those "wow" moments...

girrrrrrr2 (author)westfw2007-07-30

wow that isnt much to have in a room... when now you can buy 1gig in a thing the size of a dime...

Cyberscann54 (author)girrrrrrr22011-04-15

try 32gig now in 2011 times are changing heck there are cell phones out now with more power then alot of home computers

westfw (author)girrrrrrr22007-07-31

Yeah. Of all the advances in computer technology, I think the advances in mass storage have been most visible and impressive. For some reason CPU and memory have been pissed away into relative invisibility (the computer doesn't SEEM to respond much faster than ye old mainframes, even though it's doing a lot more with a lot more data.) But mass storage... Even with photos and video, the amount of storage a mere mortal can lay their hands on is clearly huge...

girrrrrrr2 (author)westfw2010-03-07

with the huge amount of space that can be crammed into a small stamp sized hdd i think we should kinda put the we need more memory thing on hold and develop faster parts for the computers, and cheaper ways to make the parts also.

solpredator (author)girrrrrrr22010-03-04

Your statement is funny!   I remember years ago hearing people say "2 Gigabytes??!  Can you ever run out of space with that??"

SandLizard (author)solpredator2011-02-22

Hah! I remember when some people thought no one would ever need more than 64KB.

Razanur (author)Sharingan Silk2012-05-06

And after one year you just had to pay 600€ extra in electricity bills. Running a whole computer with 100+W just to run a few harddrives? It should at least do firewallinf for LAN stuff and participate in some of these scientific projects (like BOING).

throbscottle (author)2012-03-19

You've put into writing what's been in my head for years - good job sir! Pity I don't have a workshop...

Another idea for all those old computers lying around - connect them together with ethernet and run SSI (single system image) Linux on them - looks like one computer to the user. Space could be a problem though...

Kociubinska (author)2011-04-14

One good reason why this instructable is useful is that you can never have too many computers (though my wife thinks otherwise) and buying several state of the art machines is not a good solution. And the volume of replies is another proof of its usefulness.

jomac_uk (author)2010-12-19

When i first glanced at this instructable, i wondered if it was a waste of time, and was about to move on. I read it and it got me thinking, what else could be added to make this a dedicated workshop PC, Im involved in programming PICs, and that could be added, a technical database for PDF's and the list is endless. Add a variable supply fed from one of the rails, Maybe a decent oscilloscope as well as the sound card?

In hindsight, this is definately a 10 out of 10 instructable

h3rcul3z (author)2010-08-29

Thanks, Can you take it one step a head and show us how to make an oscilloscope probes as well as a signal generator probes.

tayebz (author)2010-08-09

i amhj a beginner so particular cmments avialable now.

davidprosser (author)2008-12-12

Finaly something to do with my crappy pc's lying about! I have an old one which works beautifuly on linux, so i think i will strip it of most of its apps, slap in a 5gig hard drive and hard wire a front panel for connectors for labsupply and terminals for oscilloscope :D

Saitam (author)2008-02-24

Thanks, this Oscilloscope from Sound card inputs thing wrilly helped me allot.

Odin49 (author)2007-12-26

I checked this site and the product is not free, but it has a 14 days free trial download.

sysadmn (author)2007-12-01

Here's another idea. If your lab/bench machine running Windows/Linux, and the software you need only runs on Linux/Windows, download the free VMware Server and a free VMware virtual machine. Install the software in a virtual machine you run only when you need that software! Have a "CAD" machine, an embedded development machine, etc.

Coleston (author)2007-11-18

Wow! That DSG link is JUST what I have been looking for. Kudos++ to you, much appreciated.

sysadmn (author)2007-01-22
1 Mhz USB digital o-scope: ( )

  • Very simple hardware design; most functionality provided by software.
  • Two 8-bit channels, each configurable as 8bit analog input or 8 digital inputs.
  • Sampling rate: Tunable in 8 steps from 50kS/s to 10MS/s.
  • Live transmission of data stream allows storage of nearly unlimited number of samples.
  • Analog input sensitivity: 1Vpp or 2Vpp, DC coupled with 2.5V common mode.
  • Digital input: Schmitt trigger, 3.3V or 5V CMOS levels.
  • USB-powered operation.

Another Design: ( ). Note that the FTDI USB interface is a $19.95 part nowadays - no trying to solder a 32 pin MQFP!
gabolema (author)2006-11-20

Hi! What would be the difference (besides the current) between that and a variable transformer (the one we with our electric appliances (1.5 to 12V) . Couldn't the transformer be used as well? (they aren't that expensive)... Thanks!

westfw (author)gabolema2006-11-21

Aside from the current capacity (which is a moderately big deal), a lot of the inexpensive "variable power supplies" are not regulated, which means that they could put out 7+V at light loads on their "5V" setting (if they even HAVE a 5V setting; since they're usually aimed at battery replacement they tend to go 3, 4.5, 6,... Also, this project yields a supply with 4 simultaneous outputs, so it can be equivilent to 4 of the inexpensive wall wartsm which starts to amount to a cost that is larger than "free."

suenoverde (author)2006-11-02

"Next time you buy a new computer, you should consider the cost to the environment of the faster and more powerful chip in the box, say researchers.
A study by a team at the United Nations University in Tokyo has found that, weight for weight, the average computer chip does more harm to the environment than the car. "


uCHobby (author)2006-10-29

I have an article about using the PC to supply power to electronics projects at

pmetro (author)2006-07-16

it's the old aurgument wheather the software requirements drives the hardware or visa versa. Maybe vista will require more graphics power but do you really need it ? 98 works fine and I agree if you max out the ram of an older machine it's sufficent for most applications. Also if you keep most of the older software, photoediting ,wordprocessors , DVD mp3 media players etc, they work just as well as newer computers, if you don't have the need to be cutting edge you can get many years out of a machine

zjgz (author)2006-07-10

i'm still using a brick-like 133Mhz laptop

ian (author)2006-06-16

I've read about TV tuner cards being used as high speed o-scopes (40 MHz?). I think there is even a certain chipset that has an auxillery input. I like the serial port monitor you mention. I will use that in the future.

Spoonman (author)2006-06-16

While I liked the idea you've presented, I must say I'm surprised by your initial comments. I still use a 1Ghz machine on a daily basis (it's a laptop) and use it for everything you said you can't use one for. About the only thing I can't run on this is Doom3. And, yes, it runs Windows. People are so influenced by Intel's marketing that they feel they have to just toss a perfectly good machine just because it doesn't match up with the specs they released five minutes ago.

rotor (author)Spoonman2006-06-16

I still use a 333MHz machine on a daily basis. Works just fine as long as you don't expect it to play games made in this century. What kills old machines is typically lack of RAM, not slow cpus - while you can run firefox just fine on a 333MHz machine, you just aren't gonna see decent performance if you try to run it on a machine with 128mb of ram.

Ismael (author)rotor2006-06-17

Indeed. I ran windows XP on a P2 300Mhz with 192Mb of RAM. It ran nicely. Don't expect to play newer games on it, but for browsing/email/old games/torrents it runs perfectly fine.

westfw (author)Ismael2006-06-17

You might do an instructable on "tuning" XP to run on older systems, especially with smaller memory. When my daughters PC showed up with 128M ram, I remember a HUGE difference in apparent speed depending on whether I used a picture or a pattern for the desktop background, for instance. XP has lots of eye candy that you really don't need.

spinach_dip (author)2006-06-16

This makes no sense. For people still running the older hardware this instructable means nothing. For people who have newer hardware, why would they dedicate an old work station to the job, wasting electrcity and space, when the new computer can also do everything?

westfw (author)spinach_dip2006-06-16

I, for one, use my good computer for a lot of things OTHER than debugging circuits, and I'd rather NOT have it connected to experimental electrical circuits. The lab computer is not the computer with the family photos and movies, the MP3 collection, the 25year email archive, and so on. Besides, your own castoffs aren't the only source of extra CPU power and chasis; there are OTHER people's castsoffs! I have a PII 266MHz that is my , and I recently gave away an eMachines 400i that was in good shape...

mikesty (author)2006-06-16

ATM my server is running a 1GHZ AMD Athlon XP w/ 256mb - Windows Server 2000, running Apache, MySQL, Winamp + Radio Programs, Ventrilo etc. It's nice :)

radioeyes (author)2006-06-16

I still have a 333 MHz slug laying around my house! Throwing an old version of debian Linux on it and using old mid-90's hardware, I've found it to be significantly easier to hack the parts into oscilloscopes or logic analyzers. BTW, try a printer port for a better logic analyzer. Pinouts of those aren't too hard to come by.

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