Any info on this Parallel Port DAC? ut.dnst@dnst.be/

[simonb]

I have acquired an older DAC for lasershow use. It is the parallel port type, with a 25 way D Type connector. The bloke who sold it to me (for all of £2) does not have any technical data on it.

It is based on a pair of DAC0832s DACs followed by opamps, & a pair of 74ALS574BN Octal D Type flip flops.

The paper circuit diagram which came with it seems to be in Dutch, suggesting it will work with Popelscan or Mamba.

There is a website & email on the paper: ut.dnst@dnst.be/ and ut.stitchy@gmail.com respectivey, but I cannot get any response.

I have found many similar circuits, & some more complicated ones. There is a similar one at http://c4r0.elektroda.eu/_hv/lasers/...an_RGB_sch.png .

This is almost identical! Except for differences with some of the pins on the DAC0832 chips:-

1) pin 8 VRef derived from adjustable pot. On mine they go to +5v.
2) pins 2 & 18 WR1 & 2. X DAC WR1 goes direct to parallel port, but Y DAC WR1 also goes to X DAC WR2?
3) it has extra opamp giving differential X & Y outputs.
Probably other differences too.

Please does anyone know if these are all generic circuits? Or if there is a definite originator whom I could contact? Is there a later circuit.

Also are there any alternative DACs or similar, preferably more modern USB circuits suitable for hobbiests, & the software to run on them?

I know about Norm's one.

Many thanks,

Simon B.

[Jimboy3625]

Unfortunately I don't know anything about the DAC

There is a website & email on the paper: ut.dnst@dnst.be/ and ut.stitchy@gmail.com respectivey, but I cannot get any response.

However these addresses your referenced are email addresses, not websites. You could attempt to email them and see if you get a response.

Good Luck,
Jim

[simonb]

Thanks,

Yes I meant emails. I tried both but they did not bounce immediately.

There seem to be lots of different variants of this DAC, some combined with PICs or AT Micros to form a controller.

I will keep looking. I think I have enough to get it to work with Popelscan!

Ta.

[Francesco]

You can try sending him a PM. He is a member on this forum.
http://www.photonlexicon.com/forums/...php/677-Dnstje

As far as I know Guido (Germany) put this schematic together and DNST modified it a little.

[masterpj]

I have acquired an older DAC for lasershow use. It is the parallel port type, with a 25 way D Type connector. The bloke who sold it to me (for all of £2) does not have any technical data on it.

It is based on a pair of DAC0832s DACs followed by opamps, & a pair of 74ALS574BN Octal D Type flip flops.

The paper circuit diagram which came with it seems to be in Dutch, suggesting it will work with Popelscan or Mamba.

There is a website & email on the paper: ut.dnst@dnst.be/ and ut.stitchy@gmail.com respectivey, but I cannot get any response.

I have found many similar circuits, & some more complicated ones. There is a similar one at http://c4r0.elektroda.eu/_hv/lasers/...an_RGB_sch.png .

This is almost identical! Except for differences with some of the pins on the DAC0832 chips:-

1) pin 8 VRef derived from adjustable pot. On mine they go to +5v.
2) pins 2 & 18 WR1 & 2. X DAC WR1 goes direct to parallel port, but Y DAC WR1 also goes to X DAC WR2?
3) it has extra opamp giving differential X & Y outputs.
Probably other differences too.

Please does anyone know if these are all generic circuits? Or if there is a definite originator whom I could contact? Is there a later circuit.

Also are there any alternative DACs or similar, preferably more modern USB circuits suitable for hobbiests, & the software to run on them?

I know about Norm's one.

Many thanks,

Simon B.

I still have that diagram on my pc.
do you need it?

[simonb]

Yes please. It would be usefull. Are there any circuit schematics for USB DACs??

[edison]

I,m not sure but is this one the same? :

http://link.marktplaats.nl/570159721

[MICKEY S UK]

Hi there is Chris Favreau's OSLD as detailed here:

http://www.photonlexicon.com/forums/...Show-DAC-(USB)

[JasonB]

Hi SimonB,

I think what you have might be a Popelscan DAC, that flip-flop (used as a latch) is a dead giveaway, I think its used to latch and reset the Red, Green and Blue laser states. If you could post a picture, that would help. If it is in fact a parallel port Popelscan DAC you will probably want to build or purchase at least a soundcard USB DAC. The op-amp circuits are all pretty similar, there are some good ones posted here in PL.

Personally, I breadboarded the Popelscan DAC and played with it for a while, it plays .MOT files not .ILD. It works fine and was lots of fun but moving to a USB DAC will give you access to many more more software and shows ... c4Ro appears to have done quite a bit with Popelscan; I think it is more popular over in Europe. I believe the development of it has been frozen for quite some time.

Jason

[simonb]

Thanks Jason,

It is indeed a Popelscan based piece of hardware, although I think I read it may work with others.

Seems to be a pair of 800 series 8bit DACs followed by Opamps to provide adjustable gain, offset etc. also providing bipolar (+ve & -ve) output. But mine has not got the differential outputs, it only has signal & ground for X & Y drives to my galvos. Differential output capability would give better/less noise on the outputs, but I don't know if I would see the benefits, providing I keep the wiring short & screened, & utilise good design techniques. The circuit diagram also shows a pair of octal data latches for as you say the RGB laser output enables, but also to control smoke machines (it said - not sure if/how the software supports this?)

The board is built on verso board rather than a PCB. I could design a PCB layout in UltiBoard, but would it be worth it? I think I would be better using my enthusiasm against a more modern USB design. I have heard that the performance will be slow, as the only parallel port laptop I have is an old Pentium 2, but then again I only have 10k galvos. The most concerning part of the board I have is the 25way D type connector that interfaces to the PCs Parallel port. It's ribbon cable, but connected directly to the Veroboard, I.e. not using terminals & there is no mechanical strain relief.

What are the options for self-built USB DACs? I know there are Norms DAC, something Linux based(Bilda?) etc. & all the sound card variants. But I hear so much contrary information about these.

I am nervous about using PC/computer based software in a safety critical application such as laser (audience) scanning! I come from a military avionic design background, where it is (was) uncommon to have aircraft or weapon systems based on computer systems that are prone to failure. You don't want your flight control system to suffer a 'General Protection Fault', 'Please press F7 to reboot before hitting the ground'! In fact it was only a decade ago that if you opened the Processor Interface Unit of a certain helicopter, you would discover multiple Z80 processors, arranged in parallel to provide redundancy if one fails, plus much more circuitry to reduce the risk from failure. Also the software would be written in low level assembler, & accredited with some serious quality assurance; mainly very extensive testing;often going as far as static code analysis, whereby every line of code is assessed for possibility & effects of failure. Plus regression testing every time any change is made.

Very expensive! & maybe necessary for nuclear power stations, hospital life support systems, aircraft, the space shuttle etc. but maybe not required for a lasershow system. (Maybe I have a bit of a dinosaur way of thinking still, as things are certainly changing).

I have gone off topic, sorry! But any DAC advice you may have would be most welcome.

My thanks,

Simon Bond.


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Sent from my iPad2:-
Simon.D.Bond MEng, BSc(Hons), IEng, MRAeS.
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