I can't afford a 'scope and don't really have room for one either. But I have been reading about sound card scopes. I am well aware of the frequency limitations and I don't expect great accuracy. But it does look like an inexpensive way to get an image of what is going on in a low frequency circuit. If you have experience with one or even better one you like, please let me know. Also, if it really is a waste of time, please tell me why. Thanks.

 

I tried one after hearing about them, but never took them seriously because I have multiple scopes. If you don't have a scope, they're better than having nothing; but only if they're free.

 

Velleman (and perhaps others) make some very inexpensive PC scopes, such as this one: https://www.ebay.com/itm/Velleman-W...717174?hash=item33e3a730f6:g:WxQAAOSwz71ZOfJk

My first scope in the last 20 years was a Velleman HPS-5, which is limited, but probably still better than a sound card scope. That exact model is discontinued, but a used one is on eBay for approximately $23.00 + shipping. Search: Velleman oscilloscope

What specific sound card scope are you considering?

 

A fried just bought the latest version of this https://hackaday.com/2017/11/09/review-jye-tech-dso150-oscilloscope-kit/ scope.

https://www.jyetech.com/Products/LcdScope/e150.php

He's impressed.

 

I accidentally found this thread PC Oscope by Wendy some years ago which had a lot of good info.
I wonder if anyone, including Wendy, ever actually made one?

 

I have considered the DSO but it is my understanding that it does not allow both x and y axis to be measured--as in a curve tracer. Please ask your friend if I have misunderstood the specs.

 

What bandwidth do you need?
Also, what input voltage range?
If you wish I can show you how you can build your own PC Scope and learn some programming at the same time.

 

What bandwidth do you need?
Also, what input voltage range?
If you wish I can show you how you can build your own PC Scope and learn some programming at the same time.

That's an interesting offer but I really don't want to put you to any trouble. At the moment all I really would like to do is to make some charistic curves of diodes--a learning experience rather than with any goal. A real problem is my small muscle control makes soldering to a small board nearly impossible.

I did program--back in the day--in FORTRAN 4 but I have not even been in the same room with an Ardino or Pi. If you will take just a minute or two to outline what you would be able to show me how to do it, I could probably tell whether it is in my ability level.

Or, maybe I could save up for a Hantek (sp?). Thanks.

 

You will be measuring voltages with a device for which it was not designed. He aware that if you make a mistake you can blow out your sound board or worse. You might be better to buy a PC based oscilloscope. There are plenty of cheap ones out there. Sure you can still blow of the oscilloscope but a lot better doing that than blowing up you PC.

 

Having an oscilloscope and graphing the I-V curve of a diode are two different things.
Which one do you really want to do?
Choose one, not both.

 

Having an oscilloscope and graphing the I-V curve of a diode are two different things.
Which one do you really want to do?
Choose one, not both.

Well, I have to admit that I am a novice but I am under the impression that I need a scope to get an I/V curve. Or lots of patience and a variable voltage supply. Where do I go wrong?

 

You didn't go wrong, just slightly misguided.

You need to define the objective first and then choose the right tools to fulfill those objectives.
For example, if you want to see device I-V characteristics curves, an oscilloscope is a possible tool but not the only tool. Also an oscilloscope alone will not show I-V curves. You need more parts to complete the puzzle.

In summary,

1) you need more than an oscilloscope to display device I-V characteristics curves
2) an oscilloscope is not a necessary component for displaying device I-V characteristic curves. It can be done with other types of displays.

 

I'm sure you are right but I have no idea what other types of displays might be used.

I'm returning to electronics as a hobby after a 60+ year gap. I once knew my way around hi-fi audio circuits but stopped studying electronics before I learned anything about semiconductors. Now I am trying to pick up some new knowledge.

I bought a bunch of mixed diodes for very little, discovered most of the marked ones were Zeners and set about checking their performance. To my surprise, many were far more than 10% off while some were dead on. I used an 85 volt supply, a 4k resistor in series with the zener and put my voltmeter across the zener.

For instance, some marked 10 volts all measured 15; some marked 12 measured 12; some marked 2.4 measured 1.7 while others marked 30 measured 30. This is not a problem--I'm not making anything, but it is interesting, so I'd like to learn more.

 

Boy, you have a lot to learn yet. But not to worry, you have come to the right place.

Zener diodes may have a nominal zener voltage specification but that does not mean that that will be the voltage across the zener diode. The zener voltage depends on the current. If you check the data sheet of any specific zener diode you will find the test current used to characterize that diode.

Zener diodes with a zener voltage below 3.3V are rare. Furthermore, the zener voltage becomes even less defined and is highly dependent on current and temperature.

An I-V characteristics curve tracer is one quick way to see the forward and reverse I-V behavior of most PN junction devices. However, most hobbyists do not have access to a curve tracer and can usually manage without one. If you really must have a curve tracer there are ways to implement one. One such method uses any oscilloscope but it is not the only method.

 

I can't afford a 'scope and don't really have room for one either. But I have been reading about sound card scopes. I am well aware of the frequency limitations and I don't expect great accuracy. But it does look like an inexpensive way to get an image of what is going on in a low frequency circuit. If you have experience with one or even better one you like, please let me know. Also, if it really is a waste of time, please tell me why. Thanks.

Here is sound card based oscilloscope. Just download (free) and use it in minutes.
https://www.zeitnitz.eu/scope_en

 

Up to 22 kHz You need only laptop, Zeitnitz scope software (GNU licence) and microphone wires. However, if the some mis-gnd problems or overvoltage will occur, then laptop price is huh dozen of oscilloscope pricey, istn it?
www.zeitnitz.eu/scope_en

 

The one I find really useful is the Syscomp digital scope http://www.syscompdesign.com/ it is also a storage scope and is more portable than a PC card, can be used with your laptop etc.
Max.

 

Shouldn't it be fairly simple to make a board which would prevent over voltage signals from being passed to the sound card? I'm unfamiliar with OP AMPs except in a very general way but surely they can be set to clip at, say 200 micro-volts. Some visible indicator would have to signal the user that the image was not correct due to the clipping so the range could be changed. Now, I'm not asking anyone to design such a circuit, but if you know off the top of your head that it would be really complex or pretty basic I'd appreciate the opinion.

I'm also looking a an under US$100 Hantek though that's about what I normally spend over 6 or 8 months on this hobby.

 

Shouldn't it be fairly simple to make a board which would prevent over voltage signals from being passed to the sound card? I'm unfamiliar with OP AMPs except in a very general way but surely they can be set to clip at, say 200 micro-volts. Some visible indicator would have to signal the user that the image was not correct due to the clipping so the range could be changed. Now, I'm not asking anyone to design such a circuit, but if you know off the top of your head that it would be really complex or pretty basic I'd appreciate the opinion.

I'm also looking a an under US$100 Hantek though that's about what I normally spend over 6 or 8 months on this hobby.

Years ago, when dinosaurs roamed the countryside prior to the dinosaur ban and oscilloscopes were in their early years the vertical deflection was controlled by a Volts/Div attenuation/amplifier.scheme. The vertical deflection actually applied to the CRT vertical deflection plates was 50 mV/Div in many cases. Signals below 50 mV/Div were amplified and those above were attenuated. A simple Google of any of the schematics of these scopes will yield a diagram of how they worked. So absolutely you can create a vertical channel deflection system. Here is an example of the old Tektronix 1A1 Vertical Plug in for early Tek Scopes like the 545, you will see circuit diagrams in the pDF file on download.

The end result is it becomes easier to buy than build such a project. While I can appreciate your financial status investing in a PC pico scope is the best way to go.

Just My Take....
Ron

 

I'm also looking a an under US$100 Hantek though that's about what I normally spend over 6 or 8 months on this hobby.

HANTEK-6022BL $90.60 New.

https://www.ebay.com/itm/Hantek-602...455037&hash=item33d39e4c72:g:E1wAAOSwpXNZeEwY