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I am lookin into buying a circuit board that can serve as an oscilloscope.

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cavemen

Tue May 04 2010, 01:01PM

Registered Member #2008 Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118

Is this still the best thing out there i can get for the money it is worth?
The website lists a lot of 'stamps' with ICs.
Which one should I use to build a high frequency high resolution scope for myself?

Thank you.
V.T.

Bjørn

Tue May 04 2010, 01:59PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The best value for money is this one:

I got both. The LPC2119 one will do one channel at 400 kHz 10 bit. This one will do 3 channels at the same time at 1 MHz 12 bit or one channel at 2 MHz 12 bit plus 1 channel at 1 MHz.

You will probably need some help getting started but I know at least one more 4 HV member that got that module so it should not be a big problem.

Sulaiman

Tue May 04 2010, 05:56PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Don't forget the cost/time for making the front ends for these modules;
Low noise high bandwidth amplifiers and attenuators
Hardware
Power supply...........

cavemen

Tue May 04 2010, 06:56PM

Registered Member #2008 Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118

So if I buy AT ARM Stamp I will get the ability to see frequencies up to 2mhz when I set it up?

klugesmith

Tue May 04 2010, 08:14PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

cavemen wrote ...
So if I buy AT ARM Stamp I will get the ability to see frequencies up to 2mhz when I set it up?

I think Bjorn said maximum 2 megasamples per second. At that rate it would be impossible to acquire signal frequencies higher than 1 MHz without aliasing. You would need some sophistication to use it at half that frequency. If you want to simply connect the acquired dots to see your waveform, it could be useful up to 200 kHz. Do you need more bandwidth than a PC sound card input?

[pedantic] MHz is the SI symbol for megahertz. mHz is the SI symbol for millihertz.
For some base units, for example ohms, megas and millis are both practical values in 4hv topics. [/pedantic]

Bjørn

Tue May 04 2010, 09:02PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Yes, 2 million samples per second, you need about 10 samples to get a fair impression of the shape of a waveform The same applies for analog scopes, if you feed a 20 MHz analog scope a 20 MHz square wave it will show up pretty much as a sine wave on the screen.

So at 2 MHz sample rate you can see a 1 MHz sine wave but it will look pretty much the same as a square wave. If the signal is repeating you can reconstruct the waveform by combining information form several wavelengths. It is also possible to overclock the A/D converter and trade accuracy for speed. I managed to grab images off a video signal with the LPC2119 by overclocking the A/D from 400 kHz to 2 MHz.

teravolt

Wed May 05 2010, 02:08AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hi cavemen, I don't know what your buget is or if this will meet your requirments but I found thease on a priror hunt for scopes.

cavemen

Wed May 05 2010, 03:45AM

Registered Member #2008 Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118

I am buying a ET-STM32 Stamp Module.
I am not sure what kind of documentation this thing has and if it will allow me to figure out how to turn it into a scope.
Thank you, BjÃ¸rn.

Dear Teravolt, as I see all those scopes are a little more expensive with same capabilities or $250 ones with greater frequency range, but that is not what I need at this point.
You get what you pay for.

Bjørn

Wed May 05 2010, 10:39AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The documentation is on this long page:

Everything you need to know is in there but unless you have long experience with these things it can be rather overwhelming. Luckily I have figured out the important parts so with some patience you should be fine.

Do you have a favourite programming language on the PC that lets you receive data over the serial port and draw graphics on the screen?

GhostNull

Fri May 07 2010, 10:04AM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

Sparkfun makes a Digital Oscilloscope DIY Kit

costs $59.95, its 5MHz but it's resolution is a bit lower (8bit)

SparkFun wrote ...

Features:

* 9VDC power supply voltage
* <280mA current draw
* 5M samples/second (AUTO mode only)
* 8 bit resolution
* 256 sample memory depth
* 1MHz analog bandwidth
* 100mV/Div-5V/Div sensitivity
* 1MÎ© impedance
* 50Vpeak-to-peak max input voltage
* DC/AC coupling
* Save and display up to 6 captures to memory
* Transfer screen capture to PC as a bitmap file (serial adapter not included)
* Backlit LCD display

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