I need help to build a simple oscilloscope!

[Azhar]

I'm so much in need for an oscilloscope and since they are expensive I thought maybe I might be able to build one that can, at least show me the wave forms.
Are there any recommended designs for an oscilloscope that can be used with a CRT TV maybe?
any schematics?

Thanks

[Rerouter]

if you are looking at very low frequencies, e.g. under 50Khz, you may be able to get away with a CRT, it involves breaking into the coil drivers, and building a triggering circuit,

you have the trigger circuit drive a sawtooth ramp based on the desired sweep speed, controlling the horizontal, and a switchable attenuator followed by an amplifier controlling the vertical


the reason for such low frequencies is that crt's are coil driven so take time to recover from a given input, whereas most analog scopes make use of electrostatic deflection plates,

Edit: while i appreciate the methodology of wanting to make one on your own, your in aus, you can get some old analog gems for under $50, pick up,

[kripton2035]

look around in this forum, be patient, look at ebay, you can find a used decent scope for $50 (Dave had one for $19 !!!)
I dont think you can build one scope yourself for less than $50
and if you can it will be less featured than the $50 used one.
also for nothing you can have a scope on the audio card of your pc computer, limited to low frequency, but free.

[EEVblog]

Circuits that turned your TV into a CRO were very popular in the 70's. Lots of magazine articles in the archives if you go looking. Google "tv oscilloscope"

[dfmischler]

I converted a B/W TV to a scope when I was a teenager in the late '70's.  Mine was untriggered and not calibrated worth a damn (OK, it might have been a little flaky, too).  A PC soundcard oscilloscope would have been a big improvement.  If I had known where to get a real triggered scope for $50 I sure would have.

[Legit-Design]

http://www.serasidis.gr/circuits/AVR_oscilloscope/avr_oscilloscope.htm



Remember similar project on a russian forum which used separate AD converter, I think it had atmega, color display, 8bit parallel connected adc, with all the sources available. It was named Chameleon, or something similar in cyrillic.

EDIT: Found it

Really simple single layer pcb, can be etched at home.
http://radiokot.ru/circuit/digital/measure/30/ use google translate, I use the one embedded in Chrome, works really well.

The project used a microcontroller ATmega8535 and so-so it is very slow for ADC waveform digitization I connect to it 8-bit external high-speed ADC AD9280.
1.Maksimalnaya measured frequency of 500 kHz, the limits
50mv/del the measured voltage, the limits 50mv/del, 100mv/del, 200mv/del, 500mv/del, 1v/del, 2v/del, 5V/div, 10v/del.
3.Maksimalny current consumption 110mA relay enabled.
4 . the active window to the waveform 120 * 176 pixels.

http://radiokot.ru/forum/viewtopic.php?f=25&t=19878&hilit=%D0%A5%D0%B0%D0%BC%D0%B5%D0%BB%D0%B5%D0%BE%D0%BD& 350 page forum thread discussing the thing.

ADC datasheet: http://www.analog.com/static/imported-files/data_sheets/AD9280.pdf

Haven't myself built either of those, yet...



http://accrochages.drone.ws/en/node/90 some arduino oscilloscope alternatives, more can be found...

[kripton2035]

@Legit-Design:
nice simple design, but it will surely cost near $50, and a lot of time to build it
and as I said the specs are far beyond a 20MHz analog scope
and the inputs are not protected at all ...

[ddavidebor]

I'm so much in need for an oscilloscope and since they are expensive I thought maybe I might be able to build one that can, at least show me the wave forms.
Are there any recommended designs for an oscilloscope that can be used with a CRT TV maybe?
any schematics?

Thanks

I've an oscilloscope actually at 1€ on ebay XD

[Paul Moir]

I don't know why you would bother with a TV oscilloscope when you can get there with a PC soundcard type oscilloscope.  I guess it would be possible to get DC on the TV one, but that is some extra work.

Google "Sound card oscilloscope" or xoscope.

But an old CRO is the best way.  Even a 5MHz vacuum tube type if you look around local.  Those ought to be free.  I got by with an old heathkit one for years.

[dfmischler]

Even a 5MHz vacuum tube type if you look around local.  Those ought to be free.

For electronics use, yeah.  Some guy was hawking an old RCA untriggered scope at a local flea market recently who wanted 40 bucks for it "because of its cool retro look"      Barnum's law says that he will probably eventually sell it.

[free_electron]

cool retro look

That's it. i am buying my own island somewhere in the pacific where i will set up a fully equipped lab under the palmtrees. goodbye world . I've had enough of the morons in this world.

[KedasProbe]

A project that I saw when I was checking for STM32F3 projects
http://tomeko.net/miniscope_v2d/

Trying to get some luck on ebay seems like a better plan though.

[tinhead]

very simply design:

1. take something like this - ebay 251314164774
2. set scale to the middle
3. rotate the case by 90°

ready!

when you need strorage oscilloscope add a small pen a piece of paper - ready.

Such design is "green", retro looking, cheap, lightweight, pure analog (with pure analog storage)!

EDIT: wondering now how long it takes to see first chinese clones of my scope ^^

[ptricks]

If you just want to see low frequency stuff then use a sound card interface. It isn't ideal but it can show waveforms fairly well. I used one once to record IR remote control signals. Simply connect the output of a standard 38Khz ir module to the line in .
http://www.lirc.org/ir-audio.html
http://zelscope.com/

[c4757p]

EDIT: wondering now how long it takes to see first chinese clones of my scope ^^

I found one!!

[free_electron]

it may actually be cheaper to hire someone in china, give him a pen and paper and have him draw the waveform for you ...

[MrAureliusR]

free_electron is not far off... you could hire a whole team to draw animated waveforms!

but seriously, I looked into building a basic 'scope' using an old CRT TV... and basically, it ends up being useless. Yeah, you can see a waveform, but whoop-dee-doo, you can't take any measurements, there's literally nothing you can do but sense the presence or absence of a waveform. Trust me, you're going to want more functionality than this!

[TerminalJack505]

...and, ironically, you will most likely wind up needing an oscilloscope to debug your homemade oscilloscope circuit.   

[ivan747]

very simply design:

1. take something like this - ebay 251314164774
2. set scale to the middle
3. rotate the case by 90°

ready!

when you need strorage oscilloscope add a small pen a piece of paper - ready.

Such design is "green", retro looking, cheap, lightweight, pure analog (with pure analog storage)!

EDIT: wondering now how long it takes to see first chinese clones of my scope ^^

Pffft...

True compact analog storage and playback and dual channel, just attach 2 pens:

http://i382.photobucket.com/albums/oo269/CrowLogik/AKAIPosingsm007.jpg

[Azhar]

I've an oscilloscope actually at 1€ on ebay XD

You must be joking!!

[Azhar]

I don't know why you would bother with a TV oscilloscope when you can get there with a PC soundcard type oscilloscope.  I guess it would be possible to get DC on the TV one, but that is some extra work.

Google "Sound card oscilloscope" or xoscope.

But an old CRO is the best way.  Even a 5MHz vacuum tube type if you look around local.  Those ought to be free.  I got by with an old heathkit one for years.

Because I already have an old 5" crt tv, and I thought it would nice to use it as a scope! but now I changed my mind, after reading all the replies I realized even if I build one it would be a useless oscilloscope!

[IonizedGears]

Well, pretty useful if all you need is the shape of a waveform but for measurements, you would have better chances with a potato.

[poorchava]

You could fiddle around with microcontrollers and build your own DSO.  There's a guy on polish electronics forums by the nickname drzasiek who builds miniature scopes around popular microcontrollers. You can see a translated description here:http://www.edaboard.com/thread218091.html. There's also his webpage http://www.drzasiek.cba.pl/oscyloskop3.php (you will need translator for that).

Anyway, many microcontrollers nowadays have high bandwidth ports or quite fast ADCs:
-stm32f407 found in discovery boards has 3 adc which can be interleaved for up to 7.2MSPS (and since it's a SAR type ADC you can overclock it to achieve higher speed but lower reqolution - nominal is 12 bits).
-arm microcontrollers often have external memory interface for connecting external flash or ram, but they can quite often be reused as fast and DMA enabled data i/o
-PICs have a thing called PMP (parallel master port). Notable pic32's should be able to run that port at rather high rate

I will not be high spec, but it's better than nothing

[ddavidebor]

I've an oscilloscope actually at 1€ on ebay XD

You must be joking!!

Now is 1.5€

[M0BSW]

http://www.instructables.com/id/How-To-Make-A-CRT-TV-Into-an-Oscilloscope/   There's loads more on google and  you tube

[ignator]

I'm so much in need for an oscilloscope and since they are expensive I thought maybe I might be able to build one that can, at least show me the wave forms.
Are there any recommended designs for an oscilloscope that can be used with a CRT TV maybe?
any schematics?

Thanks

You have a PC, look on eBay for a USB oscilloscope. Find one that has the bandwidth and price you can afford. Some may come with the source code, so you can add your own features.

[Paul Moir]

... you can't take any measurements, there's literally nothing you can do but sense the presence or absence of a waveform. Trust me, you're going to want more functionality than this!

Unfortunately this is also pretty true of most older vacuum tube era oscilloscopes.  Even the old textbooks refer to an oscilloscope as something that lets you visualize a wave but not really measure it; primarily a qualitative instrument.  Then Tek came along and fixed that.

[Legit-Design]

Most of usb oscilloscopes are crap, especially the cheap ones.
Most of the advertised specs aren't even true.


If that holds true for scopes which cost the same as true digital scopes, are the even cheaper ones even worth considering.
There might be exceptions, but usually they cost more money. Is it worth spending money on something that is almost certainly toy/useless, when for little bit more money there are serious tools available?

[ignator]

Most of usb oscilloscopes are crap, especially the cheap ones.
Most of the advertised specs aren't even true.


If that holds true for scopes which cost the same as true digital scopes, are the even cheaper ones even worth considering.
There might be exceptions, but usually they cost more money. Is it worth spending money on something that is almost certainly toy/useless, when for little bit more money there are serious tools available?

Note that Azhar, the OP, can't afford any COTS scope. So this OP was looking to make one. For $20 you can get a 8K sample USB scope. I bet it's junk.  I have no clue what the OP is trying to measure. I didn't see anyone ask about that. But I doubt if a homemade TV scope in the end would have any more bandwidth then the lowly-est of dirt cheap USB purchased from any China vendor.  And if one was found with source code, the OP would get all the learning fun they would ever want.

So Azhar, what is your budget? What are you trying to measure? Do you have an idea of what bandwidth you want? Do you need a storage scope?

[alm]

It should be possible to find an old analog scope for $20. Even Dave managed to . Even an old tube-based beast (eg. Tek 5xx series) will be a lot better than a crappy DSO or TV-based scope.

[Sigmoid]

You have a PC, look on eBay for a USB oscilloscope. Find one that has the bandwidth and price you can afford. Some may come with the source code, so you can add your own features.

Well... He has a PC. That has a sound card.
Next, get a freeware sound recording software that lets you zoom in on the waveforms.
Then, hack together a basic high pass filter and a voltage divider to get AC coupled line level input.
Tadam, 4kHz DSO!

As good as (or better than) anything you can build at home using microcontrollers. Of course a $50 old analog beast will leave it standing, but hey, it's free.

[Azhar]

It should be possible to find an old analog scope for $20. Even Dave managed to . Even an old tube-based beast (eg. Tek 5xx series) will be a lot better than a crappy DSO or TV-based scope.

Trust me I tried! I have no luck with ebay! 

[Azhar]

Note that Azhar, the OP, can't afford any COTS scope. So this OP was looking to make one. For $20 you can get a 8K sample USB scope. I bet it's junk.  I have no clue what the OP is trying to measure. I didn't see anyone ask about that. But I doubt if a homemade TV scope in the end would have any more bandwidth then the lowly-est of dirt cheap USB purchased from any China vendor.  And if one was found with source code, the OP would get all the learning fun they would ever want.

So Azhar, what is your budget? What are you trying to measure? Do you have an idea of what bandwidth you want? Do you need a storage scope?

I need a scope to start with, i.e to use it as a beginner, I am studying electronic engineering at uni but I don't have access to the uni lab all the time, therefore I need one on my bench at home!

Now I realized it is better to find an old scope than building one yourself, esp with an old crt tv! after searching and reading I found out it's gonna be useless!
Anyway thanks to you all. it was very helpful and interesting to read all your replies

[kripton2035]

It should be possible to find an old analog scope for $20. Even Dave managed to . Even an old tube-based beast (eg. Tek 5xx series) will be a lot better than a crappy DSO or TV-based scope.

Trust me I tried! I have no luck with ebay! 

with ebay it's not a question of luck (sometimes yes) but mainly of patience !
make automated searchs to warn you by email as soon a something you want is out
then follow it, note the prices, and then if something similar pops out, you know with some precision the final price.

you can also use a nice program like auctionsieve to search for what you need

[alm]

Local pickup will often get you better deals, especially for large, heavy scopes that are expensive to ship. Try your local equivalent of Craigslist. Of course this is somewhat dependent on the population density and type of industry in your neighborhood.

[Azhar]

with ebay it's not a question of luck (sometimes yes) but mainly of patience !
make automated searchs to warn you by email as soon a something you want is out
then follow it, note the prices, and then if something similar pops out, you know with some precision the final price.

you can also use a nice program like auctionsieve to search for what you need

Thanks for the advice! will try this prog

[Azhar]

Local pickup will often get you better deals, especially for large, heavy scopes that are expensive to ship. Try your local equivalent of Craigslist. Of course this is somewhat dependent on the population density and type of industry in your neighborhood.

I tried such sites! and the cheapest I found is $170
http://www.gumtree.com.au/s-ad/hawthorn/other-electronics-computers/oscilloscope-bwd-826-50mhz-2-channel/1024681672

[alm]

Patience may be helpful, a better deal is bound to come along.

[Sigmoid]

It's a good idea to use the ended listings function on eBay, that will give you a realistic idea of the price ranges. My research results, for example:
You can get a good Hameg for $50 or less, but you may have to wait months for it (at least on the US site). With these rebadged white flashy BK Precisions, Tenmas and similar, you may need to wait significantly less for a bargain. For a Tek that's in working order, be prepared to shell out above $100. For an iconic Tek in good working order, $250-$500.
Personally I just bought a Tek 2225 from a university surplus batch, all the controls are in place, no external damage, seller says is in working order and was in use until recently. He was selling scores of the things, most in far worse shape (knobs missing, etc... students are barbarians... XD) It was $130 with well below $20 for shipping. If it works good, that sounds like a fair price.

[Dajgoro]

Local pickup will often get you better deals, especially for large, heavy scopes that are expensive to ship. Try your local equivalent of Craigslist. Of course this is somewhat dependent on the population density and type of industry in your neighborhood.

I tried such sites! and the cheapest I found is $170
http://www.gumtree.com.au/s-ad/hawthorn/other-electronics-computers/oscilloscope-bwd-826-50mhz-2-channel/1024681672

Hah, I was in the same situation, no scope, and nowhere to buy it.
I found cheap ebay deals but shipping to my country would be more expensive than the scope itself!
In the end I had to pay ~300$ for a local second hand one.

[Azhar]

Patience may be helpful, a better deal is bound to come along.

we have nothing other than patience!