Recomended DAC?

[chw9999]

oh sorry my mistake !!!
I did not se the "t" after the "i" lol :roll: :roll:

Same follow-up problem here Probably a blind spot over the "t" ;-)

Cheers
Christoph

[James Lehman]

I have a request of this forum...

Could someone direct me to the best and most cost effective printed circuit board design and manufacture?

I would like to make a board for the output correction amps needed to make a DC modified sound card work for laser. The schemo is on the web...

http://akrobiz.com/laserboy/p_laserboy_95.html

I would like to stick with a through hole design. Single sided should be fine. I have made a couple of these boards on proto typing PC board, but all of those wire jumpers is a pain!

Thanks! James. :o)

[liteglow]

some days now and yadda will be back I think !

He maybe have more info. that can help you

[yaddatrance]

Hi James! Welcome to PL, excellent work you've been doing!

I just got back from a big show and I'm still crispy 'round the edges...
Let's see if I make any sense... The key with manufacturing is conservation
of actual square inches... it's the same amount of work to make a single sided
as a double sided PCB so use the extra layer of traces to make the board more
compact.

If you're not exceptionally skilled at Protel or any of the commercial
PCB layout packages, I recommend saving yourself the pain and going
straight to expresspcb http://www.expresspcb.com/ and using
their software... We like using Protel and we send out to A&C here in
Los Angeles for professional projects, but I always end up using
expresspcb for simple boards since I don't have to worry about netlists,
electrical testing, etc... Their software is very usable (more so than Eagle
in my own personal opinion)... And protel is both painful to learn and
expensive so don't bother unless you can get free classes out of your
company.

Their 3 boards for $51 is a deal if you carefully "drill" subboards into their
2.5"x3.8" sizes... This is a steal if you keep in mind that a proper stencil
alone costs $300!


JayDC's updated circuit which uses expresspcb

You probably already know this, but one thing I would recommend adding to
gain yourself the largest marketshare you can, is to support differential
signalling by pairing another set of opamps per axis. One in a unity gain, and
the other inverting... The quad-packages work beatifully for this... Most
high-end scansystems use differential signalling and the costs of those
systems are coming down.

One possible gotcha from the schematic that I see is that
5.1V zener/-5.1V ref/-12V bridge configuration... Your voltages will drift a bit
based on load drawn from the vref. Using one of the unused opamps in the
quad package in a unity gain configuration between the output and the vref
will keep the drifting down to a minimum.

Let me know how it turns out! It's great to have other active laser folks around!

[yaddatrance]

some days now and yadda will be back I think !

He maybe have more info. that can help you

Ha, speak of the devil or something

[yaddatrance]

Oh yeah! I was going to add, make sure you add the DB-25 ILDA connector on
the manufactured PCB itself! It's a pain to support the connector otherwise.
If you don't want to go throughhole since the connectors are so big, a nice
trick is to place pads on the edge of the board such that they line up with
a standard DB-25 connector.


I didn't have a board with this done to it handy so heres a mockup

[James Lehman]

yaddatrance!

Nice to hear from you. I must admit I have been looking at a lot of your posts. It looks like you really have something great going on there. I wish I was a bit closer to the action like you are. I wish I had some other geeks to work with and get all excited about new stuff. Sometimes it's hard to keep working on this when it seems like there is nowhere for it to go. I guess the fact that it runs in Linux is the part that scares most people away. I've been trying to drag a friend of mine away from Visual Basic and into the new and uncharted world of Linux C/C++. That's not going so well.

My next big goal for LaserBoy is to turn it into a server process that sits and waits for requests for action. Then I can build a user interface that runs completely outside of that process and even other processes that run separately to do things like push data out the sound card, etc. My plan is to design a web based front end to control the whole application set.

Right now LaserBoy is a single thread application with a command line interface. You have to open a terminal into the Linux box via ssh from another computer. The keyboard into that terminal is your control device and the terminal provides text feedback as to what LaserBoy is doing for you. The running application also takes over the video card that is in the Linux box and turns it into a 24 bit color vector display at whatever resolution you can support. I run a Matrox card at 1600x1200. On that display you can see one frame at a time of whole 3D frame sets in any rotation. You can fly through all the frames in order, backwards or forwards. You can apply all sorts of effects to the data and see the results. You can select frames individually or in series groups and either delete the selection or trim to it. You can open ILDA or DXF, either to replace the contents of memory or to append to the end of what is already there. You can save the data as dxf, ILDA or even render it to bitmaps or generate ASCII C++ code that reconstructs the data. You can turn all of that data into a multichannel wave that plays back to emulate a constant frame rate, that you can set. All of the important rendering concepts are settable; dwell points, max scan angle per sample, etc. The wave is written with subcode information to be able to open it and pull out only the unique vector information that is necessary to get back the memory object that went into it. The vector information is kept in an extremely mutable data object that is all based on my own types conglomerated using C++ Standard Template Lib <vector>s.

For as much memory as it can eat up, it is pretty amazingly fast! As long as you stick to realistic data, that can actually be shot with real galvos, there won't be tens of thousands of points per frame. But just for kicks and something neat to look at on a computer monitor, you can create animations that have a ridiculous amount of data. All of the math of optimizing the data for wave works at any sample rate. Some day, surround sound cards will come out that really can do 192KHz. As it is. 48KHz isn't so bad if you know how to squeeze every bit into every sample!

James. :o)

[James Lehman]

If anyone is interested in getting into Linux and using the frame buffer for direct to video card rendering, then this is the card for you!

http://www.surpluscomputers.com/stor...&item=CRD10178

I have a bunch of these cards and they work great in Linux. I've done all of my LaserBoy development with these cards and the 32MB version.

I've also gotten LOTS of stuff from this vendor and they are fine.

James. :o)

[yaddatrance]

That's a good deal! I just ordered a couple

[eric343]

Regarding PCB manufacturers, you can't beat 4PCB/Advanced Circuits' $33 each deal (minimum 3 unless you're a student). The board size can be much much larger than ExpressPCB -- 60 square inches! (or 7.75" on a side if it was square)

You also get such niceties as solder mask and silkscreen, and the board quality is top-notch.

The caveat is you have to submit Gerber files -- which means using EAGLE (the free version won't support the full board size allowed by 33each.com), Protel, or your otherwise favorite full-featured board layout software.