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Building a Cheap Oscilloscope Using Your PC?

Cliff posted more than 12 years ago | from the but-where-would-you-plug-in-the-probes dept.

Hardware 247

JohnMadison asks: "As a engineering student, I have a lot of projects, but not much test equipment at home. I was wondering if anybody has advice on using my PC as an oscilloscope. I've downloaded a couple of shareware programs that use the sound card for input, but they weren't really useful. I am looking for a good way to make a cheap, yet decent scope. Any sugestions?" While something like this would be an interesting hack, I'm at a loss as to what you would use for probes. The submitter mentions using the sound card as an input, but would that be the best solution? If you were going to make a custom add-on to the PC to do this, what would it need? Does such an add-on already exist? Interestingly enough, this fits in well with an earlier article we did.

cancel ×


If this is an FP (-1)

Fecal Troll Matter (445929) | more than 12 years ago | (#2673365)

I'll suckie suckie yer throbbing hot member.

that slurping sound you hear... (-1, Offtopic)

Anonymous Coward | more than 12 years ago | (#2673593)

is my cock in your mouth

Shut up, you infant anal spasm. (-1)

KingAzzy (320268) | more than 12 years ago | (#2673617)

JonKatz is watching you. You should know better.-RecTalWarT

Soundcard fool (-1, Troll)

Anonymous Coward | more than 12 years ago | (#2673368)

use your soundcard, fool

eat a cock taco

RAdioshack? (1)

ender_wiggins (81600) | more than 12 years ago | (#2673370)

They have some inexpensive Scope type software/hardware...

Re:RAdioshack? (5, Informative)

Breakerofthings (321914) | more than 12 years ago | (#2673399)

Radio Shack "ProbeScope" ... about $100, plugs into your serial port, uses 9v battery for power ... comes with pretty decent software (16 bit win, but I have seen linux software that claims to support it).
It also has a little lcd screen that will show you the waveform, and will act as a digital multimeter.

Re:Radioshack? (2, Informative)

Hal-9001 (43188) | more than 12 years ago | (#2673526)

I think it might be this one [] . If not, check out this page [] to see the other options available at Radio Shack.

Yet another person who has never heard of Google (-1)

The Turd Report (527733) | more than 12 years ago | (#2673381)

Lame lame LAME!

What is this Googlehmesh you speak of? (-1)

Fecal Troll Matter (445929) | more than 12 years ago | (#2673467)

Eat shit, troll! []

Hmm... (1)

Merik (172436) | more than 12 years ago | (#2673389)

Wouldn't the pc cause problematic interference to any readings taken?

Re:Hmm... (-1, Troll)

Anonymous Coward | more than 12 years ago | (#2673469)

No. Go back to Pokemon, little boy.

Re:Hmm... (1)

Doppler00 (534739) | more than 12 years ago | (#2673682)

Most likely. Just the signals coming from the CPU or any other device on the motherboard would interfere. This would be especially true with a low quality sound card.

ep (-1, Troll)

Anonymous Coward | more than 12 years ago | (#2673390)

This early post for Ida! She's Cool!

Need better inputs! (3, Interesting)

multipartmixed (163409) | more than 12 years ago | (#2673391)

The sound card might offer reasonably sensitive voltage comparisons in the 1V range, but really wouldn't be an ideal way to go, IMHO.

Looking at the game ports (two ADCs each) might be one option, and probably "safer". (Game boards are practically free).

Another might be look at the tape port. You have a true IBM-PC, don't you? :)

Re:Need better inputs! (5, Informative)

Colin (1746) | more than 12 years ago | (#2673478)

Game ports don't actually have ADC's on them. The standard design is to discharge a capacitor, then charge it through the resitance of the joystick pot, and tim ehow long it takes to get to a specific voltage. This is related to the resistance. So, you can't use the game port for measuring voltages directly.

Picotech [] have addons for PCs to convert into a datalogging scope. I've never used one - and note that they tend to connect via the Parallel port. You can't get a whole lot of data through that port, so a 100Mhz scope won't actually show on the screen in real time. This doesn't usually matter, but you do want to bear in mind the delay between the measurement being made, and it actually appearing on the PC monitor.

On the plus side, they normally have data processing facilities that you only find on top of the range digital scopes - things like "trigger before", and FFT's.

Re:Need better inputs! (2, Informative)

Nate Eldredge (133418) | more than 12 years ago | (#2673518)

Do the game ports really have true A/D converters? I seem to recall reading that since the joystick input is just a variable resistance, that the game port just puts a capacitor in series with that resistance and times how long the capacitor takes to charge to some predefined level. So this wouldn't really be useful for sampling variable voltages.

I suspect the main issue with the sound card is the low sampling rate. 48 KHz isn't fast enough to see a lot of the signals you might want to see, especially in electronics. So any other approach would have to sample much faster. You'd need special hardware for that. Then if it gets too fast (into the megahertz), you start to have the issue of whether the CPU can read and process the samples that quickly.

I think there's a reason why oscilloscopes are usually dedicated hardware. I suspect you'll be better off trying to pick up an old/used scope for cheap. Unless you have especially high-speed circuits, an older analog one should be sufficient for most purposes, though maybe not as sexy as the latest 824 GHz digital networked uber-scope in your lab :) Try surplus stores, or see if your university has old ones they're trying to get rid of.

Re:Need better inputs! (2)

Rothfuss (47480) | more than 12 years ago | (#2673866)

reasonably sensitive voltage comparisons in the 1V range

What are you smoking crack?
The sound card microphone Line In typically has a threshold of around 100 millivolts, and probably a 2 order of magnitude span. 2 orders is just fine for a scope if you can select your magnitude. A preamp could be used if signal is too weak, but this would cost real dollars. If signal is too hot, you just play the parallel resistor game and scale it to whatever you want.

Score 3290478290432, Insightful. (-1)

Fecal Troll Matter (445929) | more than 12 years ago | (#2673393)


An electronic instrument that produces an instantaneous trace on the screen of a cathode-ray tube corresponding to oscillations of voltage and current.

Latency is a problem (5, Insightful)

SilentTristero (99253) | more than 12 years ago | (#2673400)

I've done this with some of the freeware Windows scope programs out there (I'm a former VLSI hardware designer), but even at 96kHz the latency vs. buffer size issue gets to be a problem when probing around in a circuit. It's marginally acceptable for tuning up tape deck heads and so on, but don't try it for any serious design or repair work.

The other problem is of course sound card inputs are AC, you really want DC coupling. And high impedance.

Bottom line: you're better off with a scope board from the back pages of one of the magazines.

Re:Latency is a problem (-1, Flamebait)

dimator (71399) | more than 12 years ago | (#2673888)

you're better off with a scope board from the back pages of one of the magazines.

All I see are penis enlargement pump ads.

Bitscope (4, Informative)

bfoz (200416) | more than 12 years ago | (#2673410)

Try this []

Re:Bitscope (-1)

Fucky the troll (528068) | more than 12 years ago | (#2673522)

moderator - you'd better be a regular oscil-thingy user.. otherwise how the fuck do you know this is informative? it may just be some cheap shitty program that does nothing like what the guy wants. even though the guy is a cocksmoker. and so are you. and so is everyone here. cocksmokers.

Re:Bitscope (-1)

Fecal Troll Matter (445929) | more than 12 years ago | (#2673537)

My names Fecal, and I, I, I, I'M A COCKSMOKER!)#! Thank you.

easy - winamp (0, Insightful)

PhiberKut (9428) | more than 12 years ago | (#2673412)

Winamp has excellent visualizations. Use the soundcard as the input, then customize winamp...use visu. plugins.

Third Post (-1, Troll)

Anonymous Coward | more than 12 years ago | (#2673413)

#3 bish!

Re:Third Post (-1)

Fecal Troll Matter (445929) | more than 12 years ago | (#2673432)

That was way off, too bad.

Parallel Port (3, Interesting)

JMZero (449047) | more than 12 years ago | (#2673414)

I built one a while back out of a A/D chip and a few transistors. The only other part was a clock chip and crystal. I didn't bother to sync everything perfectly - I just let the clock chip flap away and read whatever was on the lines.

Worked pretty well. It even worked as a video in(though it didn't get much resolution).

This is a really fun project if that's what you're looking for - and it's good enough for simple electronics. You'll certainly be able to see simple wave shapes. That said, you'd have to do some work if you were

1. Were worried about accuracy
2. Needed fast sampling
3. Deal with large ranges of voltages. Mine dealt only in 0-5 volts.


Re:Parallel Port (2)

kzinti (9651) | more than 12 years ago | (#2673448)

2. Needed fast sampling

Don't forget the sample-and-hold circuit!


Re:Parallel Port (1)

astrophysics (85561) | more than 12 years ago | (#2673508)

I don't think the clock chip is really necessary, If you're willing to read whatever voltage it's giving at the time.

Re:Parallel Port (2, Informative)

JMZero (449047) | more than 12 years ago | (#2673611)

The chip I had needed a clock signal in order to go through the sampling cycle - there are likely those that don't, and they might be more suited to this application. Actually the Intersil ADC0802LCN looks like it might work very well...

I tried using the parallel port itself to generate the clock signal using one of the status lines - but it didn't work as well (random errors). I don't have enough design knowledge to know why.

In any case, a fun project for a programmer like myself.

Re:Parallel Port (2, Informative)

jrockway (229604) | more than 12 years ago | (#2673631)

It is; you have to ask (pull a pin up) the A/D converter for a reading. The timer ensures that you get one on the lines every n seconds; this way your software doesn't have to ask and wait for a reading. It just gets one.

parapin (2, Informative)

jamesmartinluther (267743) | more than 12 years ago | (#2673709)

On the parallel port software interface side, I have successfully used the parapin library [] in my pc-to-breadboard experiments. This way you can spend more time on the hardware and the imaging and less on the hardware interface.

"parapin makes it easy to write C code under Linux that controls individual pins on a PC parallel port. This kind of control is very useful for electronics projects that use the PC's parallel port as a generic digital I/O interface. Parapin goes to great lengths to insulate the programmer from the somewhat complex parallel port programming interface provided by the PC hardware, making it easy to use the parallel port for digital I/O."

- James

CPU Fan (1)

Renraku (518261) | more than 12 years ago | (#2673417)

I'd say if you had a board that can take measurements from the CPU fan and power supply fan, you could use that as a base of measurement, because they can usually tell you how much voltage is coming in. All you'd really have to do is make it update fast enough, and write some 'ware to put it into a graph form...

Re:CPU Fan (1)

smokin_juan (469699) | more than 12 years ago | (#2673718)

Slick idea, but I wonder what sort of sample rate the MB has. If the diagnostic software is any indication a one second sample rate won't buy you much in terms of quality. The idea of hooking a voltage straigt to the borad makes my eye twitch a little too... Needs a buffer.

Takes up some space, but... (1, Interesting)

Anonymous Coward | more than 12 years ago | (#2673424)

Why not just buy a real 'scope? I got mine for $170. 20MHz, two channels, external trigger, all the usual stuff. Plus it looks slick sitting under my monitor.

Need Analog to Digital conversion (1)

obtuse (79208) | more than 12 years ago | (#2673426)

You'll need something to convert the Analog signal to a Digital signal for you computer to display it. That's what your sound card was doing. Not a lot of inexpensive commodity level A/D converters I can think of. I don't think software sampling will help much, otherwise you wouldn't have specialized hardware on the sound card.

Ask Slashdot FAQ: 1. Ask Google First (4, Funny)

Anonymous Coward | more than 12 years ago | (#2673430)
found from bt nG=Google+Search

Re:Ask Slashdot FAQ: 1. Ask Google First (3, Insightful)

Rick the Red (307103) | more than 12 years ago | (#2673514)

And for just under $400! Uh, but at that price, why not just buy a stand-alone 'scope?

Sound card inputs not good (1)

jridley (9305) | more than 12 years ago | (#2673438)

Caveat: I haven't done ANY research on this, but...

I wouldn't think sound card inputs would be of any real use, except to check out the waveform. They're not going to be calibrated for voltage, and if you did calibrate them, I can't believe they'd be very stable.

But the big problem is that those inputs are going to be intended for AC input. They are BY DESIGN intended to ignore any DC component of the input; they do so typically by a capacitor isolating the input. This is exactly what you DON'T want.

If you're really interested in this kind of stuff, just pick up a copy of Nuts & Volts [] magazine at better newsstands; in the back you'll find hundreds of classified ads for lots of hungry garage inventors and small manufacturers producing, among other very interesting toys, input cards to do exactly this sort of thing.

There are some good A/Ds out there (1)

PacoSuarez (530275) | more than 12 years ago | (#2673440)

There are inexpensive A/D chips that can be easily programmed from a PC. They can store the data they meassure in a small local RAM and then transfer it to the PC.

I know that some guys use these A/Ds for things like "listening" to the stars using a radio with a parabolic anthena. Probably some E.T. searchers can help you here.

Dataq Windaq starter kit (2, Informative)

Hal-9001 (43188) | more than 12 years ago | (#2673441)

I think you might be able to get started with a DATAQ WinDaq starter kit [] . Specifically, the DI-194 [] is only $13 + S&H for a four-channel, 8-bit DAQ that you just plug into your serial port.

Re:Dataq Windaq starter kit (1)

avandesande (143899) | more than 12 years ago | (#2673550)

240 samples a second isn't very useful for this

probes (0)

schematix (533634) | more than 12 years ago | (#2673451)

probe this...
Go into your closet and find a metal coat hanger. Cut it and straigten it out. Go to radio shack and pick up the microphone style jacks for the end. Solder the hanger to some wire and attach the jack on the other end of the wire. Wrap some electical tape around the hanger so you have a non-conductive grip. Plug it into the line-in or the microphone port.

The only problem i could see with this is if you are testing something with a high enough voltage, you may end up roasting that brand new SB Augidy card.

Couple links (5, Informative)

dimator (71399) | more than 12 years ago | (#2673455)

I was looking for something along these lines as well, a couple months ago. The software/sound-card solution is xoscope [] . I'm afraid I haven't had time to try that.

Another cool site is [] where you can find a completely open-design for an oscope you can build yourself (or order from them, I think.) It includes all the schematics and such, and the finished unit slides into a bay in your PC, with two slots for probes. How cool is that!

Try National Instruments' LabVIEW (2, Interesting)

ScooterComputer (10306) | more than 12 years ago | (#2673460)

It is rather expensive...but if you are still in school, you can get an education version. The data acquision cards are also rather pricey, but I have seen refurbed ones, and older models, go for cheap.

You should be able to get good acquisition speeds and LabVIEW is a really cool programming environment. They may even have a demo. The coolest part is that since it is a programming environment, you can collect your data and actually DO stuff with it at the same time.

test (-1, Offtopic)

cachimaster (127194) | more than 12 years ago | (#2673463)


I've got you all beat (2, Interesting)

m.dillon (147925) | more than 12 years ago | (#2673464)

Find an old Commodore Pet computer on the junk heap somewhere. Turn it on, make sure the monitor still works, and extract the TTL digital input wire from the internal monitor cable while leaving the remaining wires connected. You can then use this (and ground) to probe TTL signals up to around 7MHz :-)

Alternatively you can go to CompUsa and spend $60 on a cheap oscilloscope.


Re:I've got you all beat (0)

Anonymous Coward | more than 12 years ago | (#2673668)

CompUSA sells oscilloscopes???

Parallel Port (2)

lizrd (69275) | more than 12 years ago | (#2673466)

I seem to recall building an quite a few sensors in electronics lab in college that used the parallel port. As I recall, the general scheme was to attach the input to a 741 op-amp circuit to increase/decrease the voltage levels as needed. The output of the 741 is then used as the input to a 8 bit analog to digital converter chip. Data can then be collected easily by polling the parallel port.

Re:Parallel Port (0)

Anonymous Coward | more than 12 years ago | (#2673603)

Please use opto-isolation! I remember an op-amp
/opto isolator pair in one package that worked.

I'd hate to see your computer fried.

Re:Parallel Port (2, Informative)

Doppler00 (534739) | more than 12 years ago | (#2673699)

Actually, a buffer IC (74244 or 245?) should be adequate to protect the computer unless your running a few hundred volts through your op amp!

somewhere on the old hd... (1)

astrophysics (85561) | more than 12 years ago | (#2673468)

I have a very old circut diagram and MS QuickBasic program for an 8 bit osciliscope that used the parallel port. Most of it could easily be translated to C, although I'd guess there's a much better library for reading data from the parallel port. It worked fine for about $50 of electronics from DigiKey. We used it mostly with a photocell for some simple interferometry experiments. It also worked with a microphone and I'm told someone else used it for a moisture sensor of some kind. I suppose I probably could dig it up if you're really interested, but there must be people who have done a better job since.

O-scopes rule (-1, Offtopic)

Anonymous Coward | more than 12 years ago | (#2673477)

Probes are good for probing.
is good for trolling.

Compiling a kernel gives me a massive chubby.

Limitations (1)

jdc180 (125863) | more than 12 years ago | (#2673484)

I think that using anything but an expansion card would limit resolution and range tremendously. Not only would voltage resolution be low, but you wouldn't be able to pick up high frequencies. I can't think of a port on a standard PC that would allow you to pick up anything but small signals at low frequencies.

The expansion card that would be needed would have to be huge, the heatsink alone would be large compared to the card It would also think that it would have to connect directly to either the case powersupply or it's own. All in all, I think such an expansion card would be impractical. I'm sure you could design such a card that could operate in a small range, but one that could perform as a bench O-scope is impractical.

they do make Oscilloscope Cards (1)

blonde rser (253047) | more than 12 years ago | (#2673488)

I'm sure the poster is already aware of these (and is looking for something cheaper) but I thought it was still worth mentioning. They are generally cheaper than most Stand alone units I've seen. But most of the cheap ones I've seen only come with windows (and sometimes mac) software. If I remember correctly Rp Electronics [] sell a few. They are pretty cheap all things considered... I've had text books that are of a equivilant price to some of these.

Some computer O-scopes type projects on the net... (4, Informative)

cr0sh (43134) | more than 12 years ago | (#2673496)
http: // uk/~ih/doc/adc_dac/deck/4chan 8bitadc.asc ac/deck/8chan 12bitadc.asc dac/adc11/ c/dcfg/ html#pcme asuring

Have fun...

This approach could work: (1)

NickFusion (456530) | more than 12 years ago | (#2673497)

This is the best approach I can think of.

Start with one of these. []

Then, with a couple of 20 cm bits of duct tape, attache one of these [] to the front.

Helpful Links... (4, Informative)

jyak (112533) | more than 12 years ago | (#2673502)
- Information on Oscillator circuits co pe.shtml
- Website about a homebuilt 'scope ml
- Scope diagrams and schematics
- Company with PC based products

Hope this helps...

National Instruments has great instruments as PCI cards and you can make your own programs/software in Labview but this option is on the expensive side.

Oscilloscope card (1)

FieldTheory (245045) | more than 12 years ago | (#2673503)

I did something like this as a term project for an electronics class. My version was a PC/AT card, but it shouldn't be that hard to do a PCI version. It's not that expensive (around $150 for all the parts, the blank card being the most expensive) and fairly simple to construct. And it has a little sine wave generator on it also.

The idea was to run the signal into an ADC, then run the output bits through octal line drivers and transceivers (74LS244's and 245's) connected to the system bus. Bus commands were interpreted using a bunch of logic gates (real cheap). I guess without getting into too much detail, I'll just throw out other part numbers: a 688, 240's, 04's & 08's, and the test oscillator (sine wave generator) built out of a DAC and a 4046 voltage controlled oscillator.

How cheap? (4, Insightful)

Jeffrey Baker (6191) | more than 12 years ago | (#2673510)

How cheap are we talking about here? You can get a Tektronix 465 with a probe for $200 or less and this is a nice featureful scope. There's a reason the 465 was in production for decades. It's many times better than some sound card hack.

Get an Electronics Magazine (1, Informative)

Anonymous Coward | more than 12 years ago | (#2673515)

I used to be in your same situation as an EET major a few years ago. My sugguestion is to go buy a copy of Popular Electronics. Inside you will probably find a variety of ads for such a product. The products usually run about $99 and come with software, interface, and more than likely, probes. I even recall an article which described how to build one and gave out the software for free. So you might try contacting them (P.E.) to see if you couldn't recieved an old issue (I know they make CD's for such a thing).

What kind of oscope do you want? (2)

Nelson (1275) | more than 12 years ago | (#2673528)

If you're doing fairly low sample rate stuff, you might be able to use a soundcard, parallel port, or custom PCI card.

I've done a fair amount of debugging with logic analyzers and digital osciliscopes (software stuff, I'm not a hardware jock) and you couldn't debug an IDE interface or PCI interface with something on a parallel port or sound card, at least not easily. If you're doing simple analog stuff you could get away with it. Realistically you're going to want a real scope at some point in time though.

Hard to say though. I've seen them at hamfests and stuff like that for relatively cheap and any decent hardware shop is going to have them for their people to use or "check out."

jameco has really cool oscilliscope cards (2)

Kris Warkentin (15136) | more than 12 years ago | (#2673529)

Try this [] site (click on the catalog page for a pdf spec sheet). They have a card that turns your pc into a scope for like $300 bucks (vs thousands for a regular scope).

It's easy! (2, Interesting)

nephorm (464234) | more than 12 years ago | (#2673536)

Well, maybe not easy, but you'd need a few things:
1) An A/D chip. You can also make one yourself by following schematics from any standard analog electronics book. It just takes a voltage (let's say 5 V) and converts it into it's digital equivalent (which would then be 101). You can build a converter yourself out of cheap parts from radio shack, assuming you're using low currents.

2) Some sort of clock. One easy thing is to build it as a parallel port device. This'll take a little bit of hardware (not a whole lot, though), and you can use the computer to clock the thing. Or, of course, you could build a PCI/ISA card, but that seems like more of a hassle.

Assuming you don't need bidirectional communication on the device, you could just have a straight-through connection to the parallel port (I think), and just write a program to poll the port and plot the data. Hmm, this might be a fun project for me to try later...

A harder (and maybe more useful) project would be to try to make a Digital Logic Analyzer... these things are REALLY nice when working on digital electronics.

Anywho, the standard disclaimer of my irresponsibility ;-) applies... Also, I'm assuming that you're talking about working with low wattages. A hand-wired A/D converter can handle whatever wattage the individual resistors are rated for (though you need to make sure that you aren't blasting out the parallel port), whereas the A/D chips can end up with pretty low max voltages.

I did this with a generic DAQ and VB (1)

Harper (5397) | more than 12 years ago | (#2673542)

I took an electronics class were we had to build and program a oscilliscope for one of the beginning prohjects. We had a generic DAQ [] and the api for C(dos) or VB(win). The prof only new VB so we were limited to that. The drivers and API for VB was pretty good, however it was quite slow when propagating sample rate changes and the like. However, it worked. If you are interested in the source code it is here [] (warning - it is VB and it is a quick hack). We were able to use it to "record" from a microphone and then "playback" the waveform we recorded. It was pretty cool.

really you should be able to use any analog-to-digital acquisition device. A sound card would work great. Program it using the sound cards low level API. Basically write a driver/program that parse hthe wave info and spits it out to the screen rather than the speaker. heh.

For probes, use a mic plug hooked to a male banana clip. that should allow you to use any breadboard/probe.


O-Scope 'n the PC (3, Insightful)

ackthpt (218170) | more than 12 years ago | (#2673555)

Hopefully someone can set you up with a way to do it, but what I've seen is often worse than buying a good used one at a Hamfest. You should get in touch with ARRL folks in your neck of the woods and find out when and where Hamfests take place. Granted, you may have to shell if you want a good storage scope, but some decent scopes can be found. My dad has a soft spot for Tektronix scopes.

xoscope, BitScope (3, Interesting)

rrwood (27261) | more than 12 years ago | (#2673557)

Some specific links:

xoscope - a software oscilloscope []

BitScope - hardware black-box oscilloscope that you control via a PC []

Xoscope is Open Source, so hack away if you don't like something about it. The SourceForge page has links to a schematic you can build to use your soundcard as the ADC, though you are of course limited to about 20kHz signals (stereo input = dual trace though). Definitely a cheap way to go.

The BitScope is a really cool design that is open or free (as in beer and speech). You can download all the specs and build it yourself, or buy preassembled kits or BitScopes (cheaper than buying the individual parts yourself). It is a black box that you control via software on a PC, which is pretty cool.

And then, you can always snag a scope on EBay for a couple of hundred bucks. Loads of Tektronix scopes, etc. Wish I could afford a Fluke ScopeMeter myself.


Velleman (1)

TheLurker (32233) | more than 12 years ago | (#2673565)

Velleman makes cool kits and cool oscopes too!
Cheack these links out: =3 47914

Can't be done with soundcard (2)

seizer (16950) | more than 12 years ago | (#2673567)

This much should be obvious - you can't use any modern soundcards, because they all feature AGC - Automatic Gain Control - which means that across certain decibel ranges, you'll be able to tell the difference, but across others, you won't.

For example, 30db might be louder than 25db, but might "look" to the sampler to be the same as 60. (Or whatever... it's logarithmic, I can't be bothered with real examples :-)

Maplins (0)

Anonymous Coward | more than 12 years ago | (#2673569)

Maplins ( do parallel port oscilliscopes - they're quite good actually.

radioshack dmm (1)

avandesande (143899) | more than 12 years ago | (#2673572)

Radio Shack has an inexpensive DMM that will interface to a computer via serial port.

OR.... (0)

Anonymous Coward | more than 12 years ago | (#2673585)

Sell you house and get one of these ?p rodid=378
it's very, very nice (i use one at work)
then again it's ~200k USD...

seriously though... if you have time, a high quality ADC can probabbly do the work for you -- couple that with a DSP, or more simply -- use your PC to analyze the data real time (including trigger and all that) -- (hint - may involve programming). should cost minimally but a LOT of time on your part. then again, may i remind you of the minimal cost.

way 3: ebay

Informer (-1, Offtopic)

Anonymous Coward | more than 12 years ago | (#2673586)

Informer []
by Snow

What's up man! Hey yo what's up!
Yeah what's goin' on here.
Sick an' tired of five-oh runnin' up on the block here.
You know what I'm sayin'?
Yo Snow, they came around here lookin' for you the other day.
Word? Word! Bust it!

Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.
Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.

Police them come an' now they blow down me door,
One him come crawl through, through my window,
So then they put me in the back the car at the station,
From that point on me reach my destination,
When the destination reached, it was the east detention, where them
Whipped down me pants, looked up me bottom, so
Bigger they are they think they have more power,
They're on the phone me say that on (every) hour,
Me for want to use it once an' now me call me lover,
Lover who I'll be callin is the one TAMMY,
an' me love her in me heart down to my belly,
Yes me Daddy me Snow me I feel cool an' deadly,
As the one MC Shan an' the one Daddy Snow,
Together we-a love'em as a Tor-Na-Do.

Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.
Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.

Listen for me, you better listen for me now.
Listen for me, you better listen for me now.
When me rockin' the microphone me rock it steady,
Yes sir, Daddy me Snow me are the article don.
But in the in an' the out of a dance them they say where you come from,
People them say you come from Jamaica,
But me born an' raised in the ghetto that's the one I want you to know,
Pure black people mon that's all I mon know.
Yeah me shoes are tear up an' me toes used to show,
Where me born in on the one Toronto, so

Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.
Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.

Come with a nice young lady. Intelligent,
Yes she's gentle an' irie.
Everywhere me go, me never left her at all.
Yes, its Daddy Snow me are the roam dance mon.
Roam between a dancin' in a in a nation-a.
You never know say Daddy me Snow me are the Boom Shakata.
Me never lay-a down flat in that one cardboard box.
Yes say me Daddy me Snow me I'll go reachin' at the top, so

Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.
Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.

Why would he?

Me sittin' 'round cool with my dibbie dibbie girl,
Police knock my door,
Lick up my pal,
Rough me up an' I can't do a thing
Pick up my line, when my telephone ring.
Take me to the station,
Black up my hands.
Trail me down, 'cuz I'm hangin' with the Snowman,
What I'm gonna do,
I'm backed an' I'm trapped,
Slap me in the face an' took all o' my gap.
They have no clues an' they wanna get warmer,
But Shan won't turn Informer!

Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.
Informer, you no say Daddy me Snow me I'll go blame,
A licky Boom Boom Down.
Detective mon said Daddy me Snow me stab someone down the lane,
A licky Boom Boom Down.

Get a real, used scope. (5, Insightful)

Matt_Bennett (79107) | more than 12 years ago | (#2673590)

I know you want to use your PC, but try to get a real live scope- you'll probably spend less money and get a better measurement device. A sound card would be barely good enough for doing audio measurements, but you run into the problem of an impedance that is too low, with too low a bandwidth. Yeah, you may only want to look at audio frequencies, but realistically, you want a scope with 3-10 times the bandwidth of the highest frequency you'll be looking at.

You don't specify what frequencies you want to work with, but for any sort of digital work I wouldn't suggest that you use *anything* less than a 30 MHz bandwidth analog scope. With that, you'll see a lot of rounding on a 10MHz signal, but you'll be able to see something. Digital scopes are very nice, if they have a decent sample rate. To get the equivalent performance of a 30 MHz analog scope in a digital scope, the digital scope must have at least a 30MHz bandwidth and 100MHz sampling rate (or a good equivalent time setting).

Bandwidth is *very* important. Oscillations can and will happen, and if it is a high frequency parasitic oscillation, a low bandwidth scope will fool you into thinking there is nothing there. You will spend many, many hours trying to debug such a circuit, because your tools will lie.

If you look around (hamfests, ebay) you should be able to find a working old tektronix boat-anchor for between $100 and $200. I've seen plenty of kits available, but they all cost more and have less performance. Since you don't say that you want to build the scope as a learning experience, you want it as a tool. The scope should be your third piece of electronic test equipment, after a multitester and a logic probe. These tools are fundamental. Get something good, whose performance you can trust, that you won't need to debug.

That was my final project (-1)

cachimaster (127194) | more than 12 years ago | (#2673598)

I am a Electronic Technic here in Argentina.
My ending project was exactly that, A osciloscope in a PC. In fact, by sofware you can also get a spectrum analyzer (16386+ bands, and a 3d one), and a function generator.
The harware was very simple: a R-2-R network and a comparator (LM311 if i remember) attached to a parallel port. It also has some Operational Amplifiers to support a voltage range of +/- 20 Volts, AC / DC
The software: named "WAVE" , all in C++, runs on a 386 with 2 MB of ram, but the 3D spectrum analyzer needs a pentium. Runs under DOS with its own Windows Manager. I can give it for free if someone wants it.
Limitations: The Parallel port has a 500Khz bandwidth, so you are limited to Audio frecuencies, with 10 samples per cicle. (Not much better that a Sound-Blaster) but that was cool back in the '96
A better aproach will be to program a Microcontroller (PIC 16F877 sure is the best choice) yo sure can get 10 Bits and 10 MHZ fron those little chips, and interface it with your computer by parallel port or something. Just an idea.

Protek Digital PC scope cards and Velleman scopes (2)

Y2K is bogus (7647) | more than 12 years ago | (#2673599)

I have one of the Protek PC ISA oscope cards. It's about a 4Mhz card and is dual trace. It works ok, but not well enough for analyzing video signals. It has some decent software and logging capabilites. It's manufactured by Hung Chang [] . Price: $220-$249

The other scope I have is a Velleman handheld. It works really well. For $249 it's the best thing I've seen. It's based on a PIC microprocesor and is single trace with a 5Mhz bandwidth. Some of them have PC interfaces, mine doesn't. Here's Velleman's website [] .

The main problem (2)

fireboy1919 (257783) | more than 12 years ago | (#2673610)

An oscilliscope just samples input voltages and displays their amplitude. That's REAL tough computations (NOT!). And a frequency analyzer (often used for a similar purpose) just takes a fourier transform of the signal (this is a mere O(n log(n)) complexity problem). The software is trivial!

The main problem is the sampling rate of the hardware. Soundcards are made with a sampling rate that is only slightly above and below the range of human hearing, which means that for many circuit frequencies, they are unacceptable. If this will work for you, the coding is rather simple since its the well known I/O operations that have been used in PCs forever. Just learn a little bit about SOME sound API and output the wave output from the soundcard in real time. I'm sure others have done this before, too. Its a 4 hour job.

If you need better accuracy than that, you need to buy a data acquisition card, but it will cost you a pretty penny for them. Here [] is a list of some of these cards.

There are some up sides of having a card such as this that can capture high quantities of data, the biggest being that if you know C, and you get specs on ANY kind of input signal, you can often write a driver for it - NTSC signals, radio signals, digital video signals...pretty much anything.

If you really want to do this quickly, get something like the matlab and use the data acquisition toolbox [] .

In my opinion, a data acquisition device on the computer beats the pants off of an oscilliscope any day.

Idea (3, Interesting)

jrockway (229604) | more than 12 years ago | (#2673618)

I was going to build something like this a while ago, but I haven't had time. Just get a A->D chip, hook it up to a USB bridge, and read it a certain number of times a second (500, I think; most D/A converters can handle this IIRC). Connect a probe, voltage limiting circutry, and ground (and a timer, so your software doesn't have to raise the read pin 500 times a second :). Since it's USB, you can easily have another device in the box that does D/A and transposes it on a higher voltage. Then you have an osciloscope and a frequency generator. I think I'll start drawing some diagrams and investigating the IC's. Email me if you want information.

You might try.... (1)

EENinja (542200) | more than 12 years ago | (#2673622)

I would not usually recomend Radio $hack as they are always way over-priced. However, they do have in interesting DMM on sale for like $40-$50. Now I know you wanted an O-scope but the DMM I mention comes with in interface to your comp and can be used to generate graphs ect. You may want to check it out in thier December catalog or your local store :)

Forget PC, buy and old one... (1)

Giant Robot (56744) | more than 12 years ago | (#2673623)

Usually universities sell their old equipment to clearing houses, where you can get old analog scopes for cheap! (ie, less than fifty bucks CDN)

The old scopes are probably adequate for everything for undergrad EE, unless you do something that requires GHz or requires lots of DSP (like FFT on the fly...)

With most universities replacing oscilliscopes with new (expensive) digital ones, you should be able to get a cheapo old one. If you can't find one, talk to your profs or people who run the labs.

Hit (2, Insightful)

eXtro (258933) | more than 12 years ago | (#2673635)

I picked up a decent analog oscilliscope for 200 bucks. It's got 35 MHz bandwidth which is plenty for most things you can do in a home lab. This seems like a better option than the 350 dollar PC card that has 10 MHz analog bandwidth mentioned elsewhere.

sound card woes (2)

brer_rabbit (195413) | more than 12 years ago | (#2673639)

the sound card would be pretty crappy for this. First off, it's AC coupled, meaning that you won't be able to measure DC voltages. Also, it's most probably filtered for human hearing, 20-20khz.

I think there might be software around that turns the printer port into a logic analyzer. While not an oscope, logic analyzers have good value.

External A/D converter? (1)

MikeLRoy (246462) | more than 12 years ago | (#2673654)

Everyone's lookin for an a/d thats already standard on a pc... but there probably isn't anything good. Why not build a black-box of sorts, and just use the pc for display and ui?

What i mean is this: there are pic chips out there with a/d converters (16F877, although i don't know the sampling rate). Now, these chips also have uarts and support serial io. If you wrote a piece of code for the chip, it could easily measure voltage variances, timing, etc, and output that to pc in a simplified format (ie, not realtime, but already simplified). Just a thought.

Sound card = not best idea for oscilloscope (2)

AntiNorm (155641) | more than 12 years ago | (#2673665)

I've downloaded a couple of shareware programs that use the sound card for input, but they weren't really useful

You can measure low-amplitude AC signals from a few Hertz to a couple dozen kilohertz (and easily do fancy tricks such as FFT analysis), but if you're talking about using this setup as a real oscilloscope, you're not going to get very good results. Sound cards have lots of filters on them, many of which are active filters, and this would have the potential to tinker with your input signal. Also, feed too large a signal into your sound card, and poof -- no more soundcard.

TV card? (2, Interesting)

rjkm (145398) | more than 12 years ago | (#2673671)

The Bt848/878 has a raw mode which delivers the pure composite signal. I never tried to use it with non-TV signals but I guess it could work.In this raw mode the chip does not care about horizontal and vertical syncs. You can see all the "good stuff": color burst, front porch, strange "signal modifications" in scrambled channels, etc. When I programmed the Linux drivers I experimented with this mode a little bit.
This does not deliver great resolution (only 8 bit) but goes up to at least 36MHz (PAL frq.*8). With the chips with internal PLL (Bt848A and upwards) you can even change the sampling frequency in small steps.

You can find the Bt848/878 in most cheap TV cards on the market but you might have to make some modifications to the Linux driver to support
the raw mode and non-standard PLL settings.

You get what you pay for (1)

MikeLRoy (246462) | more than 12 years ago | (#2673679)

I just realized something: with the talk in this article and the other one mentioned, about hacking everyday hardware for use in a lab, why bother? Sure, lab equipment is expensive, but if accuracy and reliablility matter, thats what you pay for. When you buy a bench PSU, it puts out the voltage its marked for. Same with oscilliscopes. The reason its expensive is because its made to exacting specs. Besides, those new Tektronix lcd scopes are only like $2k CDN. And i know old highschools and university dept's selling old scopes for a couple hundred bux. Buy one that you know is good!

how to build a HIGH SAMPLE RATE osci with your PC (0)

Anonymous Coward | more than 12 years ago | (#2673688)

it's not difficult, the only thing you have to
remember if you want anything that isn't a
soundcard/parport joke but something real (100 or up to about 150 MS/s depending on the fifo you find)
AND can be used as a logic analyzer too with little
modification, is to use a fast FIFO memory.

so you buy a cheap & fast ADC, plug it to the
input of a fast FIFO memory and just let a 50 or
100 MHz oscillator fill it up as long as you sample.
Then any cheap microcontroller at the output side
of the fifo will asynchronously read the samples
ans transmit them to your pc via rs232 or usb.
If you want more than about 100 or 150 MS/s, the
limiting factor is the fifo bandwith and you have to come up with a fast switching demultiplexing
stage before the several parallelly arranged fifos.

that's all for the digital part.
BE CAREFUL: the beginner error is to flunk the
analog frontend due to insufficient shielding
and wrongly calculated impedance adaptation.

ok, that's it, son.
good luck.

More details please (0)

Anonymous Coward | more than 12 years ago | (#2673702)

Most of the above suggestions were given after assuming some required sampling rate and resolution, will you use the scope for audio or RF, what kinds of voltages and circuit impedances will you be monitoring, an idea of the performance of the computer you intend to use would also help...
National Instruments ( ) makes data acquisition boards (expensive).
some microcontrollers have analog inputs and A/D converters and some start at a reasonable price and can be programmed from a pc with a C++ cross-compiler or run basic natively & could send the partially digested signal info on a serial or parallel port.
Also, if you can get your hands on an issue or two of Circuit Cellar magazine ( ) you would be flooded with ideas...

If you have to ask Slashdot you aren't qualified (5, Informative)

Zero__Kelvin (151819) | more than 12 years ago | (#2673723)

This not meant to be rude, but rather a simple statement of fact. If you have to ask Slashdot you aren't qualified to do it. Analog electronics is Voodoo science, and in the end you will have no idea if the representation on the screen is accurate. Even if you compare certain captured signals to ones grabbed by a high end O'Scope, there will be no assurance that signals of different amplitude and frequency are properly represented.

As an Engineer who was also an Electronics Technician for many years I have seen improper understanding of the nature of Analog cause all kinds of misunderstandings. For example, using a long ground lead or improper input impedance can distort the signal so much that a perfect signal looks FUBARed, or a FUBARed signal looks good. Indeed, there is a kind of Heisenburg Uncertainty to it all. By this I mean that the act of measuring changes the results, of course. I have seen faulty circuits that only work when you are probing them!

Your best bet is to try saving up for one designed by qualified Engineers ... perhaps the ones, or another one mentioned by others. I haven't looked seriously at any of these, so I cannot offer a valid opinion one way or the other.

Also, a sound card based O'Scope is only going to handle signals in the audio range, and if the card is any good it will do some pre-processing on the inpuit anyway, further distorting the input signal, so that's way out IMNSHO.

Finally, if you do decide to do this just for fun, spend the money to purchase real (quality) probes, and learn to write device drivers if you don't have this skill already. Expect to spend several years coming up with anything that is marginally decent (based on your level of knowledge at this time, as indicated by your post.) Also, be fully prepared to never succeed and ruin a motherboard or two along the way 8^}

Whatever approach you decide upon, Good Luck!

O-scope (0)

Paracelcus (151056) | more than 12 years ago | (#2673735)

Get a used 20mhz triggered sweep scope for around $100/120.00, there cheap and nobody wants them anymore, used to be used in TV repair etc. Nobody fixes TV's anymore.

Future Slashdot Carpentry Question (0)

Anonymous Coward | more than 12 years ago | (#2673741)

Gee, I am interested in carpentry and have a lot of wood. How can i best make a hammer out of the wood?

Ans: I suggest you go out and buy a real hammer. No matter what you do you still don't have an adequate hammer and if you don't have the proper tools you won't get anywhere in carpentry. You will spend more time making the hammer than having fun in carpetry. Ditto for making nails too!

While oscilloscopes are cool... (-1, Flamebait)

Anonymous Coward | more than 12 years ago | (#2673756)

Fuck linux
Fuck Bill Gates
Fuck Usama Bin Laden
Fuck AOL
Fuck Slashdot
Fuck Linus Torvalds
Fuck Tux

Don't try to analize these lines
In this post
I say fuck
Too many fucking times

Fuck IE
Fuck Netscape
Fuck Opera
Fuck Steve Case
Fuck Disney
Fuck The RIAA
Fuck GPL
Fuck UPS
Fuck DVD
Fuck GIF
Fuck VCR
Fuck iMac
Fuck Netpliance
Fuck FuckedCompany
and fuck Slashdot again

Gameboy Digital Sampling Oscilloscope (2, Interesting)

bartjan (197895) | more than 12 years ago | (#2673760)

The dutch magazine Elektuur published a design for a device that allows a Gameboy to be used as an digital oscilloscope. See Some info in dutch about the device [] . The english sister-magazine elektor also published the design, but I can't find anything online about it, except the fact that it is published in issues 2000/10 and 2000/11.
Using Google I found a page [] with screenshots about the device.

Building a scope from a Sound Card (1)

hari (15720) | more than 12 years ago | (#2673766)

Using a sound card is fine for low frequency applications. A probe for the sound card could be
made by soldering two wires (one for the input and one for the ground) to a regular sound card connector (which can be obtained from radioshack).

Another way would be to buy a cheap DAQ (data acquisition card). Although I am not aware of any "cheap" ones.

Personally, I would buy a second hand scope from eBay, be sure to buy one with good bandwidth (anything greater than 50MHz would be ok for normal applications)

happy hacking!

Get a GPIB board (1)

hotchai (72816) | more than 12 years ago | (#2673807)

I worked at a lab where we used GPIB boards (from National Instruments) to do instrumentation/control type of work. NI cards tend to be a little pricey, I am sure you can find cheaper alternatives. You can use a GPIB board with Labview or some such software that gives you an oscilloscope-like display.

In fact, there was an article [] in Linux Journal about using these cards with Linux.

... with easy on-screen waveforms (2, Funny)

gunner800 (142959) | more than 12 years ago | (#2673819)

You need:
  1. A webcam (preferably USB)
  2. A real oscilloscope

Point the webcam at the oscilloscope. If you need greater precision, hit "full screen".

Make your own project (1)

Thor Ablestar (321949) | more than 12 years ago | (#2673845)

Disclaimer: I cannot even imagine YOUR scope market. The following message reflects my own preferences, technical and logistical abilities etc. Moreover, any decent scope costs terribly.

I believe the 50 MHz bandwidth is the minimal requirement for debugging the modern equipment (I own 250-MHz scope and in the past had a lot of troubles trying to debug the 5 MHz clocked devices with 5-MHz bandwidth scope. It means that the sampling frequency is at least 100 MHz which excludes any cheap software implementations and requires some PGA.

I also believe that the scope should be a standalone device with optional PC interface.

If you can be satisfied with 33 MHz sampling rate you may use the Scenix/Ubicom SX 100-MHz microprocessor to control any ADC and any graphical LCD display. External ADC clocking will be needed. Also don't forget that the fastest way to make a loop is to open it, so you will need 384 bytes of program ROM to get 128 dots (Maximim for Scenix RAM) at maximum speed. If you need more then look at Ubicom IP2022.

It may be a nice pen-sized scope. You may be proud of it.

For additional info: look at Ubicom [] website for microprocessors, Philips for ADC chips and Webring for PIC and Scenix related projects (A lot of! You may even find the ready scope project there).

repetition (1)

Triv (181010) | more than 12 years ago | (#2673876)

Interestingly enough, this fits in well with an earlier article we did

I think I must've seen that at least tacked onto 5 stories this week. Isn't it funny how nothing on /. is new anymore? "I was going to reinvent the wheel, but damnit, they had it on slashdot years ago."



eBay (0)

Anonymous Coward | more than 12 years ago | (#2673898)

Have you tried looking for cards on eBay?

Even better than a scope card, I got a Tektronix 60 MHz 2 channel oscilloscope from eBay for about $140. Picked that one up when I was a student too and have been using it ever since. It's definitely worth checking out.

X-Y scope : ASTEROIDS!! (2)

blakestah (91866) | more than 12 years ago | (#2673903)

The old asteroids arcade games are programmed X-Y scopes. Buy one, rip out the XY-Scope, and you are in business.
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