I need help to build a simple oscilloscope!

[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!