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Building a Cheap Oscilloscope Using Your PC?
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.
They have some inexpensive Scope type software/hardware...
Wouldn't the pc cause problematic interference to any readings taken?
--
What is the sound of this sentence?
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?
Do daemons dream of electric sleep()?
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.
Try this
Winamp has excellent visualizations. Use the soundcard as the input, then customize winamp...use visu. plugins.
Elijah Chancey www.elijahsadventure.com nomadic IT consultant, bicycling across america "all that you touch / and all
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.
-Dave
Let's not stir that bag of worms...
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...
Job? I don't have time to get a job! Who will sit around and bitch about being broke and unemployed then?
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.
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.
Assembly is the reverse of disassembly.
http://www.designnotes.com/pcs64i.htm& bt nG=Google+Search
found from
http://www.google.com/search?q=pc+Oscilloscope+
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 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.
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.
"It take 9 months to bear a child, no matter how many women you assign to the job."
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.
Scott
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 bitscope.com 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!
python -c "x='python -c %sx=%s; print x%%(chr(34),repr(x),chr(34))%s'; print x%(chr(34),repr(x),chr(34))"
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.
http://www.labview.com
Scott
"Hokey religions and ancient weapons are no match for a good blaster at your side, kid."
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.
-Matt
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.
I don't want free as in beer. I just want free beer.
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.
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.
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.
http://www.ucl.ac.uk/~ucapwas/scope20m.html: //www.ucl.ac.uk/~ucapwas/video.htmlo c.ic.ac.uk/~ih/doc/adc_dac/. uk/~ih/doc/adc_dac/deck/4chan 8bitadc.ascd ac/deck/8chan 12bitadc.asc_ dac/adc11/a c/dcfg/. html#pcme asuring
http
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http://www.doc.ic.ac
http://www.doc.ic.ac.uk/~ih/doc/adc_
http://www.doc.ic.ac.uk/~ih/doc/adc
http://www.doc.ic.ac.uk/~ih/doc/adc_d
http://www.epanorama.net/links/measuring
Have fun...
Reason is the Path to God - Anon
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.
What were you expecting?
http://www.epanorama.net/links/oscillator.html
s co pe.shtml
t ml
- Information on Oscillator circuits
http://www.dansworkshop.com/Homebuilt%20oscillo
- Website about a homebuilt 'scope
http://members.tripod.com/michaelgellis/scope.h
- Scope diagrams and schematics
http://www.picotech.com/oscilloscope.html
- 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.
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 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.
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).
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."
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).
In Soviet Russia, hot grits put YOU down THEIR pants.
Well, maybe not easy, but you'd need a few things:
;-) 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.
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
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.
heh.
Producing satire is kind of hopeless because of the literacy rate of the American public. - Frank Zappa
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.
A feeling of having made the same mistake before: Deja Foobar
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.
-Roy
Velleman makes cool kits and cool oscopes too!d =3 47914
Cheack these links out:
http://www.velleman.be
http://www.velleman.be/productlist2.asp?lan=1&i
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 (maplin.co.uk) do parallel port oscilliscopes - they're quite good actually.
Radio Shack has an inexpensive DMM that will interface to a computer via serial port.
love is just extroverted narcissism
Sell you house and get one of thesep ?p rodid=378
http://www.lecroy.com/shopper/configurescope.as
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
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.
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.
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.
Mod me down and I will become more powerful than you can possibly imagine!
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.
My other car is first.
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 :)
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.
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.
Chris Kuivenhoven is a thief, beware
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.
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.
-Michael Roy Some people are like Slinkies. Not really useful, but you can't help smiling when you see one tumble down
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.
I pledge allegiance to the flag...
of the Corporate States of America...
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.
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!
-Michael Roy Some people are like Slinkies. Not really useful, but you can't help smiling when you see one tumble down
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.
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 ( http://www.ni.com ) 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 ( http://www.circuitcellar.com ) you would be flooded with ideas...
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
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
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!
Guns don't kill people; Physics kills people! - John Lithgow as Dick Solomon on Third Rock From The Sun
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.
I killed da wabbit -Elmer Fudd
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!
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.
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!
In fact, there was an article in Linux Journal about using these cards with Linux.
Point the webcam at the oscilloscope. If you need greater precision, hit "full screen".
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).
Interestingly enough, this fits in well with an earlier article we did
/. is new anymore? "I was going to reinvent the wheel, but damnit, they had it on slashdot years ago."
I think I must've seen that at least tacked onto 5 stories this week. Isn't it funny how nothing on
:)
Triv
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.
The old asteroids arcade games are programmed X-Y scopes. Buy one, rip out the XY-Scope, and you are in business.
Using an ISA card is easier than you might think...
you could get an A/D converter and tie it right into the ISA buss for high speed DAQ. If you want real high speed, you could use DMA, which looked a little tougher for me.
Look up ISA interface or something similar. You should find a lot of tutorials and other info...
If you did make one, I would reccomend optocoupling the probes as to not accidentally fry your ISA bus with a nice 10 - 20KV ESD event.
As a engineering student...
As A engineering student? Y'all ain't got them grammar skills in Oklahoma, do ya?
There is a very high quality oscilloscope box from Velleman. It has it's own box and probes with software package together in the box.
They use the software package Scope-It as "digital storage oscilloscope and spectrum analyser". They also have a demo downloadable at that page.
PCS641, PCS500 (PC-Scope 50MHz) and with adapter.
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
man don't be so anal. you're not hot stuff. I'm just a co-op at IBM and I've seen circuits that only work when they are probed -- you don't sound experienced when you say that. In fact, I could have written your entire post. All I'm trying to say is that this guy asked a reasonable question and you're belittling his knowledge by attempting to portray the fact that you are knowledgable, when, in fact, you do not sound knowledgable at all -- merely annoying.
----(o)----
If you're at all serious about building up your stash of test gear, the PC is just about the last place you want to look. Nothing it can ever do, even with add-in boards, will ever equal the quality of equipment that was made for the purpose you're trying to accomplish.
Others have pointed out that you should check out ham radio/electronic swap meets for a good used O-scope. This is an excellent idea. As far as that goes, I have some suggestions.
The Tektronix 7000 series, more notably the 7603, 7704, 7904, and 7104 are all some of the longest-lived and most durable instruments that Tek ever built. My personal unit is a 7904 (500 MHz basic bandwidth on the mainframe) with a whole raft of plug-ins. If I recall my specs correctly, the 7603 mainframe is rated at 100 MHz, the 7704 at 250, the 7904 at 500, and the 7104 at 1 GHz.
Keep in mind those are MAINFRAME bandwidths (top-end response for the mainframe IOW). You'll need appropriate plug-ins to take full advantage of that. Anyway, the 7000 series mainframes need a minimum of one time-base and one vertical amplifier plug-in to be useful. I would settle for nothing less than a 7A26 (200 MHz dual-trace) vertical module, and a 7B85 (time base) module. If you can, find a 7B92A for the time base and a 7904 or 7904A for the mainframe.
If you need REALLY high-frequency response on the vertical side, look for a 7A19 (single-trace, 50-ohm input, 1 GHz response). Bear in mind that you'll only get the full bandwidth from such in a 7104 mainframe (although you can use it in other mainframes at reduced bandwidth).
A word of caution on the 7104 mainframe, assuming you should choose it: Its CRT is more delicate than those of other Tek scopes, thanks to its extremely high writing speed, so be VERY careful to check it for screen burn.
If a portable 'scope is more to your liking, look around for a Tektronix 465, 475, 475A, or 485. Hard to go wrong with those, especially if you get one that has the DMM option.
Other sources for used Tek equipment include, of course, Ebay.
OTHER TEST GEAR: I suggest HP or Fluke for a multimeter. Fluke makes good stuff, especially older hardware, but HP's is easier to get calibrated. My own benchtop meter is an HP3456, backed up by a Fluke 8520.
POWER SUPPLIES: A good bench power supply is critical to any lab. HP, Kepco, and Lamda all make excellent units. Figure out what you're going to be working with and shop around.
As for more specialized stuff, I can't comment intelligently without knowing what specific sub-field you want to go into. There are different specialty instruments for RF, digital design, microwave, power supplies, etc.
Perhaps the best advice I can offer is ALWAYS get the best stuff that you can possibly afford. NEVER sell yourself short where your own test gear is concerned! Doing so -will- come back to haunt you later on.
Bruce Lane, KC7GR,
Blue Feather Technologies
http://www.gage-applied.com/tektronix.asp
Now see here. Check old issues of Popular Electronics and Electronics Now. Popular Electronics ran a project you could build, "Turn your computer's monitor into an oscilloscope."
As to using your computer as a scope. I have done this (just yesterday.) What you require is a high speed ADC (analog to digital converter) and boy you aren't going to like the prices on those chips. Get one that can cut 100 kHz. Now get an 8651B high precision timing chip for the clock; use a rotary contact switch to change the programming on the chip to change your timing. The ACD chip and the timing chip are the basics you need. Get some coaxial (10b2 style) input jacks; run the binary input from the ACD into your computer's ISA or PCI bus (not too difficult.) There you have it. Throw in some voltage dividers to change the voltage scale and away you go. Write a program to interpret the binar input from the ADC into something that can be displayed.
This might sound silly - but eBay has usually very cheap scope's going. You need some expertize to judge their quality - and some patience. But you should be able to get away with a 1000mHz dual channel analog scope for under a 100$. I needed about 2 months of systematically bidding up to 75 dollars on each decent one. As for a digital scope - I found www.activewireinc.com a most excelent toy - it is basically a 8051 running at decent speed with 16 inputs/outputs - and easily clockable. At 10kHz you can sample from the PC (works with FreeBSD, NetBSD and linux/windoze) at higher rates you simply write a bit of 'c' code you download into the device to do the capture. http://www.oceanoptics.com makes a great PCI card which has good IO and easy to integrate. Another option is to spend 50-150 dollars on a third hand GPIB based A/D device. Ebay has lots of them and add a NI card to your PC. Dw
werd brotha.
Natural-Selection Be
I would have to agree with Zero__Kelvin-- no sound card is going to give any kind of decent signal. If you need an oscilliscope, you'd be doing yourself a disfavor by trying to use the horrible, bandwidth limited DSP in your soundcard. At the very least get a dedicated card by National Instruments or a used Tektronix/Wavetek/HP/whatever Oscope off of eBay for cheap. An analog scope will give you better resolution anyhow, and you'll thank yourself in the longrun.
Sorry, kiddies, but they're exactly right: somebody who has any business doing this wouldn't be asking here. Used scopes are cheap, and a lot less hassle.
The mystery for me is why it's viewed as such a deadly insult to point this out.
...laura
"man don't be so anal. you're not hot stuff. I'm just a co-op at IBM and I've seen circuits that only work when they are probed -- you don't sound experienced when you say that. In fact, I could have written your entire post.All I'm trying to say is that this guy asked a reasonable question and you're belittling his knowledge by attempting to portray the fact that you are knowledgable, when, in fact, you do not sound knowledgable at all -- merely annoying. "
Sounds like you should change your nick to openlysubversive 8^}
First of all, I never said I was 'hot stuff', but I would certainly compare my expertise to yours 24/7. As a person with 15+ years of real world experience beyond an IBM co-op, I can tell you that people are often surprised to see that probing the circuit can affect it's functionality.
Perhaps, if you could have offered valuable input you should have, rather than composing this little diatribe? I never once told him his question was stupid, or that he shouldn't try. I merely told him what he needs to do, and what kind of effort to expect. I also offered him advice should he choose to pursue the DIY option. Finally, if you could have written the post, and it doesn't sound knowledgable, what does that say about you 8^}
To quote captain Hulka from the movie 'Stripes', "lighten up Francis"
Guns don't kill people; Physics kills people! - John Lithgow as Dick Solomon on Third Rock From The Sun
check out www.ni.com
they make pci ocilliscopes and the such for cheap.
student discounts...
I think the replies to this question have shown what utter crap the people on slashdot write. If you don't know anything, don't write anything. I read about three replies with accurate info.
Sure, lets use a 741 as an analogue pre amp. Good idea. Even in unity gain mode, you can only get a gain b/w product of about 1MHz. Even if you use three 741 to make a constant b/w amplifier with current followers using supply current sensing, the best b/w you will get will still be about 1MHz.
Lets think about the typical thevenin equivalent cct of a scope input. It's a 1Meg ohm in parallel with a few pF. Do you really think the AC coupled sound card input comes anything like close to this? Certainly the parasitic C is likely to be much bigger on the sound card. And, as some people pointed out, it's no good for DC measurements.
Buy a scope second hand. You will come no where close to even a crappy scope by bodging something on the PC.
If you really want to do this I think you need to buy a fairly quick TI DSP and sample to the memory on the DSP. Transfer to the PC after each sample run.
Oddly enough, this semester i've just completed a Cogs 300 class (That's Cognitive Sciences, for those of you who do not know), one in which our prof got his docterate dealing with EEG's(Electroencephalography,) and such. In a nutshell, the method in which an EEG functions is by amplifying (20 000 some times) the extraordinarily minute electrical signals given off by the collective firing of the neurons in the human brain.
Term project was a biofeedback one, and originally consisted of training myself to try to produce more alpha/beta waves for communication and computer control, applicable to severly physically handicapped people with such dieases as ALS. In the later stages of ALS, it leaves its victims in such a state that one's cognitive abilities are as normal, except that you have absolutly no muscular control whatsoever.
Before you mod this offtopic, training was done via a custom A/D converter box, attached to a parallel port, and using custom software analysing the signals and such for relevant waveforms. Mind you, this software was designed with EEG analysis in mind (no pun intended.)
I just got a multimeter from RSR electronics for about $50 . It works great as a multimeter, but I have yet to actually hook it up to my computer. It only comes with Windoze 9x software, of course, but I don't imagine it would be too hard to write a Linux driver for it if one doesn't already exist. I guess I know what I'm doing this weekend...
I have been having ideals about cumtom building USB data output test equipment. From simple meters to an ociliscope where they are controlled from usb and output is solely over usb. I think a unit could be relatively small and use a small palm computer or a notebook computer for a display.
Sure they probably already exist, at an ungodly sum, or will exist by the time I get around to doing it but it should prove to be an interesting learning experience.
One is to use the parallel port as your input and a eight bit A/D converter.
With a few other parts make a far scope....
If you just want to look at simple wave forms works great.
Else you can buy a card that installs in your computer and turns it into a real scope.
don't have a URL handy...
Wise men speak because they have something to say, Fools because they have to say something!!!!
Because I couldn't find anything good that required a PC, I went out and just bought a used oscilloscope. I bought a used oscilloscope off of e-bay for ~$400 (you can find cheaper ones easily). What I did was I would search daily for oscilloscopes that worked, included probes (they are really expensive), and most importantly had a "buy now" option. I found one that a guy put up that the "buy now" was really low (considdering the scope would be over $1500 brand new). The other trick is to MISPELL things. If you search for oscilloscope, oscilliscope, osciliscope, etc... you'd be amazed what you can find. Because it's mispelled, most people don't see it and therefore don't bid on it. That way you can get things cheaper.
My last suggestion would be to go around to schools, electronic repair shops, etc. and ask if they have any old oscilloscopes you could buy cheap. If you explain your situation you'd be suprised how nice people can be.
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
Try this site http://www.datag.com
They have a free 4 channel A/D converter that run's off your serial port, comes with a nice piece of software that charts and records the data from the unit. Plus other goodies.
Wise men speak because they have something to say, Fools because they have to say something!!!!
Have to agree. It was not condescending at all. A bit matter of fact (the If you have to ask slashdot you are not qualified.....) bit is kind of matter of fact, but definitely true.
:)
You would know what kind of a tool you need if you knew more about your work. From what I gather it is like the difference in a phillips screw driver and a flat head and what type of screws they work on.
Jeremy
1 x = stick(1)
print x
sleep 1
goto 1
If you want to sample two circuits, just divide pin 1 into two wires and connect the other wire through your other device into pin 6. To use this, sample stick(0) instead of stick(1).
Maybe this will help. Good luck.
Tim ODonnell (trying to be the most
I looked into this over this past summer. The thing about scopes is that they don't need a high *sustained* transfer rate, just a high burst rate. If you've ever looked at one of the new-fangled Tektronix LCD multi-GHz digital scopes it'll be apparent that it updates the displayed data only a few times a second. Besides which, the LCD only updates at like 60 to 100 Hz. So if you're acquiring at 100 MHz for a 1000 pixel wide screen it works out to 10 microseconds per screenful. If you update the screen at 10 Hz, i.e. about as fast as your eye can keep up, 99.99% of the incoming data never gets displayed.
:)
So it seems like you'd have much better luck doing a parallel port scope if you could buffer the high-speed (e.g. 100 MHz) data stream, say with a fast 2Kx8 FIFO or an n-bit synchronous counter hooked up to a dual-port SRAM. The computer can then read the data out at its leisure through a parallel port interface. Doing simple I/O programming on the parallel port I think you get much better than the 10 kHz needed for 10 Hz refresh @ 1000 samples per screen. And you'd never worry about stupid Windoze timing making you lose samples.
IMNSHO the FIFO you'd need is pretty deep as FIFOs go; such a deep FIFO will be a few dozen dollars, and I think DPSRAMs can be had cheaper. 8-bit ADC chips are can easily go up to like 100 MHz for not too much money. Keep in mind though that this is *per channel*. You can always get wider memory for multiple channels, which should be cheaper than getting multiple IC's. And you'd need glue logic. IIRC the external glue logic in my design came out to like 20 high-speed 74xx family IC's. Or you can just put them all on a PAL. (proximity to a good EE lab with PAL burning hardware and expertise would be a plus) With a decent investment of like $100 and lots of time you should get a parallel-port scope with max speeds of several 10s of MHz at least. Try doing that with a POS ISA card and software-generated timing!
BTW get the high-bandwidth breadboard and zero-propagation-time components at your nearest physics warehouse, where you'd normally go to get massless string and frictionless pulleys
that's nothing. I have some software that works only under gdb and not on its own.
--
"It is now safe to switch off your computer."
From the the what is baudline? webpage:
Baudline is a real-time signal analysis tool and an offline time-frequency browser. It has a built in tone generation capability and it can play back audio files with a multitude of effects and filters. Designed for environmental analysis missions that range from modulation parameter measurements to searching for transient signals that go bump in the night, baudline combines fast digital signal processing, versatile high-speed displays, and continuous capture tools for hunting down and studying elusive signal characteristics.
Capture, analyze, measure, play.
Baudline isn't really an oscilloscope although it does have a waveform display. It is more of of an integrated spectral analysis laboratory with a built in function (tone) generator. Baudline currently only works with sound cards and is limited to a 192kHz sample rate.
Some folks have mentioned that computer sound cards are not really sensitive lab tools, this is true. But with a well grounded PC and a decent quality sound card like the $20 Sound Blaster PCI16 you can capture some good clean signal. For low bandwidth work the 16 bit ADC and DAC's in a PC sound card are actually far superior to the 8 or 10 bit ones that are found in todays digital scopes. So if you don't need MHz inputs, then check out baudline or the mirror, it is free, but it only runs on Linux..
great idea, then you could "render" Rossler attractors via the Chua Circuit
very neet
A quick scan through one of my magezings yields the following companies producing or reselling such products: www.linkins4.com & www.saelig.com.
Welcome to the net of 1000 lies. Upgrades are scheduled soon that should bring us to the 10,000 lies mark.
What are you talking about? Is there no one interested in a challenge anymore? Has all the fun been sucked away? Some people like climbing rocks. Some people want to slap together their own scope. So be it. I will not judge. More power to anyone that wants to do it themselves. (And more power to the person that explains it to others. ;))
"You can give a person a 'scope and they can probe for the lifetime of the 'scope. But if you teach a person to build a 'scope they can probe for the rest of their lifetime."
And a favorite just for the hell of it:
"You know, you can get a good look at a butcher's ass by shoving your head up it but wouldn't you rather take his word for it?"
National Instruments (www.ni.com) makes all sorts of digital aquisition and metering products. I've been helping with a setup that measures irregularitys in stamping presses. They have a very compreshensive set of products, and they support Linux! (and windows, and Macintosh and HP/UX, among the others).
This stuff is mighty pricey though. The digital aquisistion card's run in the USD$1500 - $6000 range, and THEN you need a breakout box to plug your sensors into.
It's some pretty neat-o stuff. Expensive, but very nice.
I'm like a chocoholic, but for booze.
http://xoscope.sourceforge.net/ (Includes directions for building buffer hardware)
c 50 /50525.htm (for a compatible probe)
http://bul.eecs.umich.edu/signal/ (spectrum analyzer that works with xoscope)
http://support.radioshack.com/support_meters/do
I'm really trying to see both sides here-- but I'm inclined to agree with quietlysubversive-- you *are* being somewhat arrogant. Professional credentials aside (I've nothing to prove, do you Zero__Kelvin? Is that why you have this (no doubt vastly finite) experience beyond he and his position?) have you considered that perhaps this guy is as much trying to gain experience with the tools as perform the test?
Perhaps you would benefit from a process like the one described;
I have seen faulty circuits that only work when you are probing them!
This is a classic case of 'i hooked up the CRO before i thought about what would happen' Do you really understand that you are effectively putting a (roughly) 1 meg ohm resistor where you measure? If you did, perhaps you wouldn't be whining; you would have got it right.
Loading effects are not a Voodoo science as you assert-- at least not to EEs. They are a reality of the testing procedure. Why? Because to *choose* the position from which results are taken, you need to understand *how* the equipment will affect you.
Your own post really shoots you in the foot.
If he's not qualified to *build* such equipment to take what amounts to results for a process of learning, he's in no position to learn. Seriously, how much mystery *is* there in (gasp) an op-amp, an A/D, and a little glue. Not much IMHO.
And don't bother belittling him because he's doing co-op for IBM. It just reflects poorly on yourself.
The best is to build a circuit with a
microcontroller and send the data to the serial
port. That way you don't have to be concerned
about the latency. Or you could buy an allready
made board for a PC.
I've used a board with an Atmel AT90LS8535
and it works great.
All you have to do is write some supporting
code at the PC with Kylix or Labview.
There are other programs available for cheap
on Linux but these two are the best.
I definitely second this. If you really want nice collection try a tektronix tds 3000. It interfaces to the pc using a gpib bus and you can control all the settings of the scope using your pc. It's fairly easily to program it from c, python or perl and it gives you 10,000 data points at up to 2ns resolution. I loved it when I had the chance to work with it. Unfortunately, it and the control program I wrote is doing stuff for superk.
"When you sit with a nice girl for two hours, it seems like two minutes. When you sit on a hot stove for two minutes, it
I know the technology exists, since I've seen telco technicians using laptops with multimeters, Osc-scopes and continuity detectors. I don't know exactly what kind of bus they use to interface it into a laptop, but the program they were using to run these was pretty cool looking.
Maybe you could contact your local phone company, or perhaps just knock over a technician and take his?
Company Part# Description
Maxim MAX197 8ch. 12bit 5MHz A/D!
Maxim MAX503 10bit D/A
Phillips 89C51RD+ 64K FLASH 1K RAM
Intel 82C55A ISA Control logic If anyone out there needs very accurate waveform data on there PC and has more time than money than this may be the way to go. I have the entire project documented and if anyone wants it I can .pdf it up and send it your way. I have the embedded c-code and the VB GUI code as well that people are free to use. It might be a good senior design project for someone to update my design to make it real time by using a faster bus like a PCI or FIREWIRE! Another great magazine that I have not seen mentioned here yet is "Circuit Cellar Ink." They have a lot of information and ads related to PC data aquisition. Let me know if anyone wants the documentation/code to build this. Makes a great stocking stuffer...
stereo input on ur soundcard means two channels of AC only (b/c of the capacitors), or what I designed into mine was to modulate the DC component of the wave into AC, and send that down one of the channels, giving u 1 channel AC+DC (would need to write software to recombine these). modulating the DC into AC has a bonus too - if u just use the amplitude of the wave to reflect the DC voltage, u can do something tricky with the frequency - use it for calibration or something. ;)
I never ended up building it, tho, but I did find a soundcard useful for serial comms debugging (one resistor or diode, and u got a logging oscilloscope) - thats really the main advantage of the computer here - a digital logging scope for peanuts (with pretty crappy resolution
I'm sorry, you are just wasting your time. I bought a HP, 100 MHz, four channel, digitizing o-scope (in cal, with 2 probes) for $124 off e-bay. Lot of places liquidate really nice scopes for very little, save yourself the trouble and buy one. Then use the extra time to study real electronics. As an aside, US Navy Electronic Warfare Technicians are required to build a working o-scope as part of their training. It was a valuable exercise, but not valuable enough to really warrent your time, believe me
I've always wondered- since your sound card is a digital to analog converter which could be used to measure the changing stregnth of an electric current, then couldn't it be used for making a lie detector (i.e. Polygraph). All you'd need would be a current source and some bare wires from somthing that plugs into your sound card- I have some headphones I could use. And of course, programs for reccording sound abound, and would work for recording the changing signal streghth.
Is a sound card sensitive enough? Or more worrisome, is it too sensitive? I haven't tried it because I don't want to fry my machine.
___
It's the end of my comment as I know it and I feel fine.
The demise of the ISA bus renders homemade
PC cards virtually extinct. An ISA card can
be hacked out in an evening from around-the-
house parts; a PCI card most certainly cannot.
Get a copy of a recent Ham radio magazine,
(73, CQ , QST) look for a ham fest near you.
They sell old equipment, scopes, parts, probes
etc...
I have never been to one around here (Oregon)
where there were not 3-4 Tektronics scopes for
sale. (These even though old are the best and are not cheap).
I bot a cheap non tek scope for $35 and RF probe
for $15. Also a good source of parts circuit board
etc.
Company is in NSW (I think), got one about 2 years ago. Great little device, bit of fun to assemble (circuit diagram only at the time) and wouldn't work for about 2 weeks due to undocumented errata.
Now there is a downloadable "Construction Manual".
One note for people in Aus. if you call up you should be able to get it at a discount (much sweeter exchange rate), or at least I did back then.
Be warned, it's a fairly heftly package that arrives, expect to be stung on the postage.
The second big question is whether you're looking at a repetitive waveform. If you are, a simple scope-type setup will work. If not, you'll need storage.
In the days of old we built them from old tube tv sets...worked good for seeing wave forms. (even at high v's, as amount of v was not a factor you were looking for) unless you were measureing v. Look in popular electronics from about 1975- '80.
How about a rental ??? few bucks-- hi quality !!
You need to take a really careful look at what you're trying to do ... it is usually better to buy an oscilloscope or a PCI 'scope card. However, if you want to make measurements in the field and keep costs down, that's a lot of extra stuff to carry around.
Corrosion measurements on aircraft is an application where a sound card is appropriate, because it meets those limitations and carrying extra equipment around the aircraft is a real pain.
It's called the Mac Classic!
;)
I just traded my Asus A7PRO for a Tektronix 2235, 2 chan. 100Mhz Oscilloscope. Maybe you can find one to. Try: http://www.radarsurplus.com/stk/tg/tg.html
Did you even bother to read the question? Or maybe you missed the very first part of it:
So he's more or less admitting up front that he's not qualified to do it, BUT THAT HE IS TRYING TO LEARN ABOUT IT. So what's your response? You flame him for even bothering to ask if something's possible!
For the sake of future generations, I honestly and truly hope that you are not involved in any sort of educational ciricuulum...
Student: Uh, Mr. Kelvin, I'm having trouble getting my equipment calibrated...
Kelvin: (sneering) If you have to ask how to do it, then you're not qualified to do it. Idiot.
Kelvin:(whirls around to glare at the class) Anyone else want to ask a question?
Students: (in unison) No, sir!
Kelvin: No questions? (muttering) How do you plan on bloody learning anything, then, you little gits...
I hope all the crap on Slashdot hasn't put you off this. I started with electronics back in the bad old days 1979. I have over the years used and even purchased several oscilloscopes. I currently use two HP 1725 275MHz Scopes. I love these units and just about any peice of HP test equipment. Most of the HP equipment I have is over 15 years old and still works great. I paid $550 for the first on in 1991 and $100 for the second one on ebay. The second one had a minor problem with the verical deflection I had to fix. I would still like to do what you are doing and build/buy a PC based scope. The hp's do there job well but won't store a trace. Also PC can do FFTs and other stuff. Let me know how you fair with this project. What you learn building this may be worth much more than a good Oscilloscope. PS: I might have asked the same question on slashdot. Not a reflection on you or your knowledge. More info from other people can't hurt. There are never any dumb questions.
Strange, a girl at my school was asking around whether I wanted any free oscilloscopes (I have no idea as to their quality). Whether they are still available or not, I don't know, but I could look into it.
"Loading effects are not a Voodoo science as you assert"
If you can show me where I assert this there is a million dollars in it for you. What I 'asserted' is that Analog is Voodoo science. Some of the best Analog experts in the industry agree with me here.
"If he's not qualified to *build* such equipment to take what amounts to results for a process of learning, he's in no position to learn. Seriously, how much mystery *is* there in (gasp) an op-amp, an A/D, and a little glue. Not much IMHO."
Designing an O'Scope requires *MUCH MUCH MUCH* more knowledge of Analog than loading effects. The fact that you think it is a matter of an Op-Amp, an A/D, and a little glue shows that you basically have no idea what you are talking about. Don't believe me? Open up a real O'Scope some day and look at the circuitry. Ever heard of Bandwidth response? Ever look at an Op-Amp data sheet? Have any idea what you are seeing when you do? Clearly not. Building a circuit that has 1:1 gain with infinite bandwidth is impossible. Never the less, that is exactly what is called for, so the professionals do their best to come as close as possible. That's what makes it Voodoo science. In fact, the fact that you think grabbing a schematic and throwing it together will work shows your ignorance even further. Perhaps you don't know what a reflection is? Perhaps you didn't realize that the length of traces and their orientation and proximity to other traces can have drastic effects on the operation of High Frequency circuits?
The fact that you think I was belittleing him for being an IBM co-op shows that you have little ability to understand what you read, and also suggests that you feel you have more to prove than you let on.
Finally, People seem to be interpreting the bold italic font as my surprise (which was a surprise some 15 years ago), rather than my pointing out something that many people will find surprising. You knew it, great. Doesn't mean most people do.
That being said, I hope you have a wonderful life
Guns don't kill people; Physics kills people! - John Lithgow as Dick Solomon on Third Rock From The Sun
I actually am a Labview programmer at my work, and I must say that if you need to find out voltages or waveforms you can't beat labview IMHO. If you need smaller voltages say from 0 to 10 volts then you can look into this board to read in your signals http://sine.ni.com/apps/we/nioc.vp?cid=1063&lang=U S This board is a cheap E series multifunction DAQ board which basically means 16 analog inputs, 2 analog outputs, and 8 digital lines. Also, someone before mentioned that you may be able to get a copy of the Labview development software for cheap if you're a student. Fortunately if you buy this board you don't even need labview to read in those signals and look at them. These boards come with a program called MAX that allows you to "test" each card, channel, whatever and it shows it exactly as an oscilloscope would. If you need more info email me at lewisder@hotmail.com
:)
good luck in your quest
Check this out...
e mo.htm
. pdf
http://www.semis.demon.co.uk/Gameboy/DsoDemo/DsoD
Not exactly a pc interface, but nifty anyway.
There is also the Pocket Sampler kit by Oatley Electronics. Not the fastest thing in the world, but worth a look. It's $25, and kit number K090. We used it in an EE class I had a few years ago.
http://www.oatleyelectronics.com/pdf/august01_kit
-JM
It is true, sound cards do have limitations when it comes to oscilloscope duty, but they are not as bad as many claim. I can't believe I'm defending the lowly sound card. It is time for some de-bunking. Let's go:
...
... can all be independently controlled via software.
Almost all measurements with oscilloscopes cannot be performed with a sound card. However, if your application meets these
Nothing you're interested in is outside the audio band (50Hz to 5kHz or so)
Low end sound cards with a 48000 sample rate are good from almost DC to 24kHz.
Up to a second delay for the screen update latency (depending on sound card) is ok
Check out a linux program called baudline, it's screen update latency is less than a 1/60 of a second. It's quickness will blow you away.
16 bit digitization (or worse) is enough
Huh? More bits is better. Since high-end digital scopes have 8 or 10 bit ADC's, the cheapo 16 bit PC sound card has far less quanization noise.
No hardware triggering (all done in software)
Why would you want hardware triggering? Deep buffers rule! In baudline you can scroll back to events that happened minutes or hours in the past (depending on RAM).
When dual channel, both have the same settings
What do you mean? Same sample rate? That isn't much of a limitation. Gain, zoom, offset,
There was no belittling there at all. Let me use an analogy: An oscilloscope helps you see what's going on in a circuit the same way that a pair of glasses helps somebody with poor vision see.
Lets say that you need glasses for your driving exam. Now anybody can grind a piece of glass... and I'm sure if you took a couple of years to learn the art you could outdo LensCrafters. But wouldn't it be far more practical to buy glasses? And if you made your own quickly on a budget do you really think it'd have the focus and clarity to let you see signs in the distance? -Quincy In the words of Pvt Winger: "That's the fac Jack"
Try the linux program called baudline, with a typical cheapo sound card, it's analog input to screen draw latency is less than 1/60 of a second. That is far from slow.
We did one for a 2nd year engineering project.
We used an 8bit microcontroller. for us we chose the a 20Mhz microchip 16F876 (although there are other better alternatives) because it had a decent amount of RAM to be used as a buffer for sampling at high frequencies. although the 16F876 has an internal ADC we used an external ADC that communicated with the micocontroller via an SPI port. this allowed us to sample at higher frequencies, and because it was a serial ADC it was cheap.
we used an amplifier to ofset the incoming signal so it was always a +ve signal so the ADC could correctly sample the wave. we used a buffer to increase the devices impedance giving a better signal.
the device communicated with the PC through the serial port. this turned out to be the largest bottle neck in the product, however was cheap and overcome using the buffer mentioned above.
a simple gui was built in vb and the device was Calibrated using a real oscilliscope.
we were able to obtain an accuracy of within 1% with the voltages the timebases.
trigering and auto-triggering implementations was trival as we other features like printing and rulers. the slew rate of the external adc was good so we were able to measure any type of wave without a problem. all this was done for about A$80 = US$40 including the case.
we found that using vb to write the gui provided an additional bottleneck as the serial comms implementation in vb wasnt all that good - and we had a relatively slow computer. so one written in C or C++ would have been nice.
So it can be done well, quite easily and cheaply.
The 741 is something like the Ford Model T of op amps. It was the first really-successful op amp, but is really outdated and a rather poor choice.
It's slow, for one. You can blow the input of an op amp pretty easily, too!
I'm out of touch, but the TL0... seriesfrom T.I. are probably still among the best low-cost ones for this sort of work.
Really glad to see interest in DIY hardware at the soldering level; we need lots more. Nuts and Volts is one good mag; Poptronics is another. Circuit Cellar is less hobby, more pro., and excellent.
_The Art of Electronics_ is a fantastically good book, well worth its cost (not cheap). Has a lab. manual, too.
HTH a bit...
Also checkout gEDA and opencores' mailing lists, as such projects have been mentioned there in the past.
I suggest that you get a real scope if you need one. You can down load data from most of them through a serial port.
If you want to design your own (a good thing for a student to do) then you need to understand how the things work.
You ought to be reading and studying instead of
trolling the internet for others to do your homework for you.
Of course there are cards to do stuff, but an Oscope is going to be a much better choice than worrying about blowing up your computer by hooking high voltages to it. What if you make a mistake?
The important characteristics of an OSCOPE are the frequency at which the thing can sample.
Doesn't your college let you borrow and Oscope? What kind of engineering program wouldn't let you? High voltage gear is just that. Computers hooked to them must be ISOLATED.
My suggestion: you can get a good used OSCOPE or lease one. Don't dick around with add-on cards.
PS: a sound card is NOT a good choice. The sampling speed to too low and the volatge only goes so high.
good luck
It isn't just sampling buy also triggering and displaying in REAL TIME.
a PC simply isn't a good choice because of the non-deterministic aspect of the software and the operating system.
You would need a dedicated PC.
Get a good used scope and don't dick around with this. If you need to measure stuff, you don't want to be spending your time designing the measureing equipment unless that is your end.
Will you go to the beach and dig up sand if you need a semiconductor? I don't think so. So leave scope design to the experts. If a scope is designed wrong you can be ELECTROCUTED.
...unless you've already had a lot of experience using one. Get an old used analog scope.
Within the last few years I HAVE finally seen digital scopes that, in addition to all the highly quantitative digital things, do a good job of replicating most of the things an analog scope does.
But you want to get beyond the naive view that taking, say, 1024 raw D-to-A samples and displaying them X/Y on a 1024x768 display is anything similar to what a 'scope does.
If you haven't used an analog scope you may have a completely mistaken idea of what a scope does. The integration of multiple traces on a slowly-fading phosphor; the effectively infinite, or at least continuous X and Y positioning on that phosphor; and the lack of any sampling/aliasing artifacts are all important.
These CAN all be simulated digitally, and these days the computing power MIGHT be sufficient to do it directly in general-purpose CPU software, but I'm skeptical...
For example, suppose you want 10,000 samples per second. The wrong way to do it is to display those signals raw. A right way to do it is conceptually is to front-end the A-to-D converter with an extremely high-quality analog low-pass filter that filters out everything above 5,000 KHz. Of course, such filters are going to filter stuff out below 5,000 KHz, too. So, the REALLY right away to do it is to a) use a very high-quality 50,000 KHz low-pass filter, b) sample at 100,000 samples/second, c) Use some FFT algorithms or convolution or a DSP chip on the data to simulate a REALLY good 5,000 KHz low-pass filter, d) display the filtered data... If the front-end analog filter can't be precision-adjusted to every sampling speed you need,then there are other considerations (filter at 500,000 KHz, sample at 1,000,000/sec, and computationally filter down to any rate you need that's lower than the input frequency). Notice that by this time, you're processing a lot more than the 10,000 samples per second you might have thought were necessary.
In the past, the people that build actual INSTRUMENTS have done these things fairly well, and the people that have built CARDS for PC's have done them poorly. That may have changed. The card or hardware you're buying should explain how all the filtering and antialiasing and stuff are done. I'd be skeptical if it would work properly unless it had its own DSP chip on it...
Kids are great, but they often do stupid things.
The kid who wants the scope should get a REAL scope. an OSCOPE should be a safe device.
The student if he starts dicking around with high voltage signals could ELECTROCUTE himself.
Voltages can be VERY high.
And, yes, there are circuits that only work when they are probed. No bull.
So. . . if the boy wants to use the scope, he should get a good one. If it is all about design, then he is going to need a real scope to verify that the one that he builds will work.
In any case, it is non-trivial to deal with high-voltages. We don't want this lazy student to get fried do we?
Can someone please tell him where he can get a good surplus scope?
Won't one of your professors let you sign one out?
P.S. You don't really want to be running experimental circuits and hooking them up to a PC, or you WILL fry your mother board.
If the software is trivial, why do you
need to go to those POSERS at mathworks.
They are going to make the next generation
graphical embedded system, ya know.
What a lie. They listed 75 jobs and didn't hire
any one.
designing a PC Oscope is NON-TRIVIAL and
DANGEROUS.
In any case if he wants to design one he needs a REAL ocscope to verify it.
PS: voltages that are measured by scopes can be
High voltage AC which can JUMP RIGHT OUT AND KILL YOU>
Or at least fry your PC, your monitor, start a fire, burn your house down . . .
And then you will have to build a new house.
Would you ask a slash dot poster to tell you how to build a house?
Leave the house building to carpenters and the scope building to seasoned engineering companies like Agilent or Techtronix.
voltages will KILL you
In contrast to the software soundcard o-scopes described by others that are limited to 0-20kHz, here is a low-cost kit that can turn your soundcard into a spectrum analyzer in the 3-500 MHz range with 1.7 GHz possible.
http://www.science-workshop.com/
Enjoy.
I've purchased to scopes off of eBay that were in good condition. Both were HP's.
I'd amend that statement a bit -- by the time you get decent results by building your own, you will have acquired valuable and rare skills in analog design and construction. And you will have had to buy or borrow a real oscilloscope in order to find out what's wrong with the one you built! I'm a test engineer. I make functional test fixtures that apply stimulus to a board and check the output signals from it. Getting DC analog signals from the board to the A/D converter accurately is harder than it looks. Audio frequencies are harder. Scopes should work at well above audio frequencies, and that gets very hairy -- every wire is also an antenna, capacitor, and inductor, all at the same time.
I might have plunged into a project like this when I was a kid and didn't know what I was getting into. I'd probably be a hell of a lot better analog designer if I had. But god, it's a big project. If you still want to go ahead, best of luck. If you actually get it working, you might as well go ahead and get the BSEE degree. Good analog designers are scarce and high-paid.
Some intermediate possibilities:
Scopes that use the PC as the display device, for instance this from JDR Micro. It's a box with the signal conditioning and A/D circuits of a low-end digital scope, but connects to a PC parallel port for displaying the signals captured. The advantages of this, compared to a standalone scope, are that you save a few hundred dollars for the scope display and control panel, and you've got the full power of the PC for analysis of the datapoints captured.
Scope card in the PC: I'm not aware of any low-end cards now on the market. The problem with this arrangement is that the PC is full of high frequency radiated signals, so shielding a scope card from that is quite an accomplishment. It can be done, but not by amateurs, or even by non-specialized EE's like me. It does have considerable advantages, as mentioned above, plus it can DMA to the PC's memory and so be able to record for longer.
Use a Data Acquisition (DAQ) card as a scope. I've done that at audio frequencies, using National Instruments MIO cards. I'd be dubious about higher frequencies, because the signal reaching the A/D converter would be quite different from the signal you were probing. (I used Labview to program it. It lets you set up a simple system fast, and there are library functions to capture data to an array, and then display it on a scope-like window. But for the test programs I was doing, after a long learning curve, I decided that for any complex program, graphical programming is inherently less efficient than typing the code as text. Labwindows/CVI is better: you create the user interface windows by plopping icons into the window, which is nice, then type in code sort of like Visual Basic. CVI is very expensive, as compared to Visual Basic and C++ development systems which work pretty much the same, except you've got to put some work into interfacing to the card. If a nice pre-written interface to the DAQ cards is worth several thousand $, then get CVI... Labview is a little less expensive; whether it is appropriate depends on how far you need to go beyond the library functions.)
Finally, whatever you do, spend about $100 for good probes. The best scope is only as good as the probe that brings in the signal.
http://www.dansworkshop.com/Homebuilt%20oscillosco pe.shtml
Now there is some serious money - I don't think that anyone that can afford a 3000 series is really going to bother with a PC-based scope replacement!
A poor attempt at a troll. Anyone who reads the original post will see that this is not what was said at all. Attempting to build an oscilloscope as an engineering student is like an apprentice auto mechanic trying to design a fuel injection system before rebuilding his first carburettor.
OK, NI stuff isn't exactly cheap, but my university spent the $$ for us to use them in our labs... You may want to bug your university to buy the NI hardware and software because that'll give you lots of precision as far as oscilloscopes go... Not to mention you can build your own instrumentation if you so desire.
What about using Bt848 A/D converter?
Any ideas?
First of all I have question. What makes a fluke DMM or oscilloscope better than the no-name brands?
Also, the poster sounded like he wanted something cheap. Labjack is $99 and reads at 8Khz, storing the results over time. It's an external box that connects to a PC via USB. It is not really an oscilliscope, but it's also not bad for someone like me - I'm not very electronics saavy but I want to get into microcontrollers. It can trace even the fastest serial communications I'll be doing, so it's great for debugging.
8 Single-Ended, 4 Differential 12-Bit Analog Inputs
±10 Volt Analog Input Range
PGA with Gains of 1, 2, 4, 5, 8, 10, 16, or 20 V/V
Up to 8 kSamples/Sec (Burst) or 1.2 kSamples/Second (Stream)
Supports Software or Hardware Timed Acquisition
Supports Triggered Acquisition
2 Analog Outputs
20 Digital I/O (Up to 50 Hz per I/O)
32-Bit Counter
Watchdog Timer Function
Easy to Use Plug-and-Play USB Device
Connect Up to 80 LabJacks to One USB Port
Complete Software Control, No Jumpers or Switches
Labjack
Notes on converting that old compact tv set or computer monitor into an oscilloscope.
s co pe.shtml
http://www.dansworkshop.com/Homebuilt%20oscillo
Wow, I think you have both gotten way too OT. There is nothing wrong with this guys post. He wants input, he wants to tap the knowledge base of the /. comunity to come up with the BEST possible solution. We often have to do that in our jobs (its a little something called teamwork). I too have my degree in EE and I know what I am doing, but still I have very much enjoyed reading peoples ideas as it gives me new ideas to try out. Earlier I had suggested he look at some DMMs that interface with the comp and someone rudely pointed out how slow that might be, well we dont know what kind of signals he is even looking at so anything to that regard is only speculation. But I would like to add THIS advise if he reads this post. If you are a student then FIND the HKN and/or IEEE guys on campus. they can often hook you up with neato free stuff (prob not an o-scope but maybe some other stuff that will help). Also, they often run labs on major campuses that are open for any one to do anything in, and they are usually stocked with scopes, ect. As for your comp, I gotta admit the guy who said use labview probably had the best idea, its pretty neat software and you may even be able to get it free/reduced price from your school. as for probes, gonna have to do some sniffing. But I feel for you, I know when I was in college spending $200 or even $100 on a scope, or anyting other than my girlfriend, was TOTALLY out of the question :)
Does anyone have experience with pico?
http://www.picotech.com/oscilloscope.html
Bitscope is a great solution, especially if you're looking to hack around a bit (ie build it), since they've got packages ranging from plans only (free) to fully assembled and tested ($lots). However, as an engineering student in a similar situation, it still wasn't worth it to me - for most of the stuff I did at home, a $50 used analog tek scope did the trick. If you *really* need a high-precision computer interfacing 100 mhz scope, use the lab! Try pawn shops for used analog scopes - I've seen quite a few for under 100 bucks in decent condition (including probes).
Maybe in the US, but here in the UK, you can earn more as a minicab driver. We have more analog designers than used car salesmen.
You left off the part about infinite input impedence...
I see even classic Slashdot is now pretty much unusable on dial up anymore.
The TDS 220 for a lot less money has automation capability with an inexpensive option module. (this was not a company purchase, but a personal one.) I have nothing else with HPGPIB, so I opeted for the communications / print module. It can be used to do all the automated stuff but over a atandard RS-232 port and includes a centronics port. I can upload and download scope setups for automated testing and capturing results. For my low volume requirements, I skip the automation and use the screen captures and hard copy to document resultes. The scope will save and recall a couple setups internally. The 3 modules you can get are, serial only, serial & centronics, and HPGPIB module. The module comes with very little useful software and a demo of a $400.00 program, however the book includes the commands so it is easy to roll your own with pearl. The important software, that is blaringly missing, was the ability to export a screen capture to a PC. (you can print OK Gotta have a reason you have to buy that $400.00 software). A quick search on Google found a freeware capture utility. (DOS and very minimal, but works)
The truth shall set you free!
. It works great for speech input. WinScope can even do Fourier Transform.
I used it to impress my girlfriend by showing her my parrot can accurately reproduce 2600MHz sinewaves.
Tired of free ipod spam sigs? Opt ou
Hi,
;-) ), 2 channels and one
;-(
I use a PC Scope from velleman. 50 Mhz bandwidth,
read 25Mhz ( nyquist
external trigger. Comes with 2 probes not attenuating, parrallel cable and power supply.
Also has decent software ( pcscope 2000 ), runs on
window$ only
It does everything I need to have and really makes
decent measurements possible.
http://www.velleman.be
I have found used Tektronix scopes on ebay at very low cost. This beats a PC-based kludge for most things, and doesn't consume your time and energy in developing software and hardware.
I bought a 60MHz portable dual-trace scope in excellent condition for $125.00.
--- Bill