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DIY Oscilloscope


2mmMark
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I've always wanted to get an oscilloscope to understand what's going on with various controllers but they've either been a big investment, a bit cumbersome or an awkward USB/PC setup.

 

There are some self assembly kits on ebay for a compact unit which looks promising so I was wondering if anyone has experience with them.

 

Here's an example:

https://www.ebay.co.uk/itm/112662652316

and a case for it:

https://www.ebay.co.uk/itm/112713808782

 

Judging by the photos, it looks like the ICs come pre-soldered, which saves a potentially tricky job.

 

It looks a lot like the Velleman style of kit, some of which I've made previously.

 

I think it's worth a punt but thought I'd ask before pressing the "buy it now" button!

 

Mark

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I built (Or assembled) a couple of those eBay kits, they are rather basic but do work and useful for showing the presence of a DCC signal when trouble shooting.

 

Just make sure the kit you buy is the one that has the SMD items factory fitted, unless you have a fine tip soldering iron and good eyes.

 

Paul

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I got an add-on for the PC from ebay. It came with a number of leads/probes (for multiple traces) and the software. Worked ok when I was fault finding on the car lpg system.

 

edit before posting:  I've just had a look, can't find any documentation, but the hardware has "www.focussz.com" on the bottom, and "FOSC-52A" on the top if you would like to search for it?

 

Stewart

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I used "buy it now" to purchase a DSO 138 O-scope.  Not being that certain of my ability to solder SMDs, I bought one already assembled (most sellers use the term "welded").  By searching around the various sellers on e-bay, I managed to find one for about $20 (U.S.) including shipping.  It's on its way, some of the shipping times for these can be quite long, but I'm not in any rush.

 

While I did use O-scopes way way way back when in college, it's been quite awhile, and for the price I figured "what the heck."  Right now I sort of want to play around with the thing to see if it is possible to reduce the "noise" interference that can mess with DCC signals.  Okay, I'll fess up . .. . I think it will be fun just to "play with."  lol

 

Before purchasing I did a search on youtube for "DSO138" there are quite the number of videos out there.

 

Hopefully I'll be able to post something here once I receive the thing and figure out how to use it and what to use it on.  

 

I should add that I skipped the acrylic case kit for the scope.  Seems that quite a few people have found them somewhat problematic to assemble, and I figure it should work fine without it.  I also skipped on buying the power supply for it as I have bunches of them lying around the house.

 

Edit to put in the last paragraph concerning case and power supply.

Edited by davefromacrossthepond
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I've always wanted to get an oscilloscope to understand what's going on with various controllers but they've either been a big investment, a bit cumbersome or an awkward USB/PC setup.

 

There are some self assembly kits on ebay for a compact unit which looks promising so I was wondering if anyone has experience with them.

 

Here's an example:

https://www.ebay.co.uk/itm/112662652316

and a case for it:

https://www.ebay.co.uk/itm/112713808782

 

Judging by the photos, it looks like the ICs come pre-soldered, which saves a potentially tricky job.

 

It looks a lot like the Velleman style of kit, some of which I've made previously.

 

I think it's worth a punt but thought I'd ask before pressing the "buy it now" button!

 

Mark

 

No experience with that one, but it looks like a well put-together kit, and for the price you can hardly lose. The bandwidth is a bit limited but depending on what you want to do with it that might not be a problem.

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My advice would be NOT to buy a kit if it will be your only Oscilloscope and if your main interest is in using a 'scope rather than building electronics.

 

If you get the kit and build it, how will you verify that it works properly without another working 'scope?

 

...R

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If you get the kit and build it, how will you verify that it works properly without another working 'scope?

 

...R

Mark could get a reasonable frequency calibration check from the mains, preferably from a step-down transformer. For amplitude a battery and a DVM will work quite well.

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Mark could get a reasonable frequency calibration check from the mains, preferably from a step-down transformer. For amplitude a battery and a DVM will work quite well.

I built a DSO from scratch years ago that connected to a PC parallel port (remember them). It would have passed those tests OK but what did not work well (because I did not know enough about it) was the analog input circuitry.

 

...R

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I built a DSO from scratch years ago that connected to a PC parallel port (remember them). It would have passed those tests OK but what did not work well (because I did not know enough about it) was the analog input circuitry.

 

...R

 

Well, yes, but there doesn't seem to be a lot of analog anything in the kit that Mark is looking at. I would think most of the A to D conversion is in the ARM processor. My guess is the kit is likely to be binary - either it will work, or it won't work at all, but from the presentation I'm inclined to think it will work. I'd consider buying one myself, but they won't ship em to the US!

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Andy,

 

If you do an ebay search for "DSO138" you'll get quite the number of sellers in both US and China that are selling. Here's one I found at random:

https://www.ebay.com/itm/Fully-Assembled-NA-DSO138-2-4-TFT-Digital-Oscilloscope-1Msps-with-FREE-Probe/262985417570?hash=item3d3b270362:g:LCgAAOSwUg9ahOkv

 

Dave

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Andy,

 

If you do an ebay search for "DSO138" you'll get quite the number of sellers in both US and China that are selling. Here's one I found at random:

https://www.ebay.com/itm/Fully-Assembled-NA-DSO138-2-4-TFT-Digital-Oscilloscope-1Msps-with-FREE-Probe/262985417570?hash=item3d3b270362:g:LCgAAOSwUg9ahOkv

 

Dave

 

Thank you Dave.

 

I have an old Dynascan 30Meg scope that's fine for a lot of things, but the capture facility in digital scopes is handy to have too. There is also the OPTAscope that I bought a while back, but it's a bit of a pain because it needs a PC. The amazing thing is that you can now buy a scope for not much more than the amount I spent on a multi-meter in the 60's :)

 

Just a thought, but If the kit that Mark is looking at works reasonably well he might want to invest in a decent set of probes.

 

Cheers!

 

Andy

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I would think that how well you need a 'scope to work will depend on what you want to do with it. I suspect that for many amateur uses, such as examining the output of a homebuilt controller, a qualitative picture would still tell you much of interest, even if the calibration were too iffy to get good quantitative data.

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Well, yes, but there doesn't seem to be a lot of analog anything in the kit that Mark is looking at. I would think most of the A to D conversion is in the ARM processor.

The analog stuff is before the signal gets to the ADC. I was using some 40 million samples-per-second chips intended for colour television. The A to D is no problem. But it is useless if the signal being converted is full of noise.

 

...R

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The analog stuff is before the signal gets to the ADC. I was using some 40 million samples-per-second chips intended for colour television. The A to D is no problem. But it is useless if the signal being converted is full of noise.

 

...R

 

Obviously, yes. I suppose it's all relative but four transistors and a handful of resistors doesn't seem like a lot to me.

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Before you do anything , you need to determine “ what “ type of signals you intend to look at , digital , analog , frequency , voltage range, are you examining rise and fall times , logic timing etc

 

Nothing worse then a scope that doesn’t let you examine what you want to examine.

 

Work out what you need then find the best fit at the price point , not the other way around

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