AD/DA and Op amp?

[Kari Laine]

Hi,

I have been playing with USB using Ztex's USB module. I plan to make an
oscilloscope and function generator.

Therefore I would need an AD and DA chip with 12 bit resolution. And
quite fast ones also. Plus I can't really handle the surface mounted
ones yet, so DIP would be good or a break out board with DIP pins.
Could someone please point me in the right direction.

Then other stupid question.
If I have understood right a AD chip only handles single polarity of
signal. I ques I need an op amp to convert from dual polarity to single
polarity - or what? Are there any example schematics in the net. I will
try with google but if someone can point me to one - thanks.

How about DA
How can I output dual polarity signals with it? Op-Amp again?

Sorry for stupid questions....

Best Regards
Kari

--
PICs, Displays,Relays - USB-SPI-I2C http://www.byvac.com
USB and FPGA boards http://www.ztex.de

I am just a happy customer

 

[Tim Wescott]

On Mon, 28 Mar 2011 19:28:22 +0300, Kari Laine wrote:

Hi,

I have been playing with USB using Ztex's USB module. I plan to make an
oscilloscope and function generator.

Therefore I would need an AD and DA chip with 12 bit resolution. And
quite fast ones also. Plus I can't really handle the surface mounted
ones yet, so DIP would be good or a break out board with DIP pins. Could
someone please point me in the right direction.

Learn how to deal with surface mount.

Then other stupid question.
If I have understood right a AD chip only handles single polarity of
signal. I quess I need an op amp to convert from dual polarity to single
polarity - or what? Are there any example schematics in the net. I will
try with google but if someone can point me to one - thanks.

An op-amp would do that, yes.

How about DA
How can I output dual polarity signals with it? Op-Amp again?

Yes.

Sorry for stupid questions....

Best Regards
Kari

I suggest that you subscribe to Circuit Cellar and/or Nuts and Volts.
Start reading the articles, and use your subscriberhood to go through the
archives. A USB O-scope is such an obvious project, it has to have been
done.

--
http://www.wescottdesign.com

 

[Rich Grise]

Tim Wescott wrote:

On Mon, 28 Mar 2011 19:28:22 +0300, Kari Laine wrote:

I have been playing with USB using Ztex's USB module. I plan to make an
oscilloscope and function generator.

Therefore I would need an AD and DA chip with 12 bit resolution. And
quite fast ones also. Plus I can't really handle the surface mounted
ones yet, so DIP would be good or a break out board with DIP pins. Could
someone please point me in the right direction.

Learn how to deal with surface mount.

Then other stupid question.
If I have understood right a AD chip only handles single polarity of
signal. I quess I need an op amp to convert from dual polarity to single
polarity - or what? Are there any example schematics in the net. I will
try with google but if someone can point me to one - thanks.

An op-amp would do that, yes.

How about DA
How can I output dual polarity signals with it? Op-Amp again?

Yes.

Sorry for stupid questions....

Best Regards
Kari

I suggest that you subscribe to Circuit Cellar and/or Nuts and Volts.
Start reading the articles, and use your subscriberhood to go through the
archives. A USB O-scope is such an obvious project, it has to have been
done.

I also wouldn't try to take on a USB scope as my first project.

Cheers!
Rich

 

[Bob Masta]

On Mon, 28 Mar 2011 19:28:22 +0300, Kari Laine
<klaine8@gmail.com> wrote:

Hi,

I have been playing with USB using Ztex's USB module. I plan to make an
oscilloscope and function generator.

Therefore I would need an AD and DA chip with 12 bit resolution. And
quite fast ones also. Plus I can't really handle the surface mounted
ones yet, so DIP would be good or a break out board with DIP pins.
Could someone please point me in the right direction.

Then other stupid question.
If I have understood right a AD chip only handles single polarity of
signal. I ques I need an op amp to convert from dual polarity to single
polarity - or what? Are there any example schematics in the net. I will
try with google but if someone can point me to one - thanks.

How about DA
How can I output dual polarity signals with it? Op-Amp again?

Sorry for stupid questions....

Best Regards
Kari

Kari:

I think this might be a pretty difficult project, if you are
not already familiar with high-speed A/D/A stuff. A
lower-speed (audio) scope is a much easier project because
you can modify an existing sound card to get DC response. I
recommend a cheap USB sound device for this purpose.

Complete schematics, board layouts, photos, and discussion
at <http://www.daqarta.com/dw_ggnn.com> "Sound Card DC Input
Modification".

The unit I show there is fairly easy to work on, and there
is room inside the metal case for the small circuit you need
to add. Connections are made to the main circuit board at
easy-to-find locations, and don't require any surface-mount
work. For example, the existing inputs are AC coupled
through small can electrolytics with through-holes, not
surface mount chips (like other USB sound devices I've
worked on), so you can easily clip them out and solder to
the leads.

Since you already own Daqarta, the other beauty of using a
sound card is that it already works with the software you've
got. Even if you were planning to use another software
package, using a sound card would still be a powerful
advantage over writing your own code.

If you need higher sample rates than 48000 Hz, this cheap
USB device won't do the job. There are cards that sample at
192000 Hz, but if you want MHz ranges this approach won't
work. But then, at MHz ranges constructing a homebrew
circuit would not be for the faint of heart... better to buy
a cheap hardware benchtop unit.

Just my 2 cent's worth...

Best regards,




Bob Masta

DAQARTA v6.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!