Newbie Intro ^.^;

[ParoXoN]

Hi!

I stumbled across this site while looking for information on laser/laser scanning standards. From lurking for a while and searching the forum, it seems I've come to the right place!

Right now I'm in my final semester of a computer Engineering degree and for my capstone project I thought it would be fun to build a simple (SIMPLE!) laser projector. We're given a basic microcomputer (ARM7TDMI-based) and told to interface it with something.

I understand the how the individual components of a laser projector work (galvos, control boards, layout) but I'm horribly lost when it comes to industry standards (DMX512; ILDA?)

For example, I found this galvo set through this site, but I'm not totally clear on how to interface with the set. I'm reading up on DMX512 but how hard do you all suppose it would be to design an interface to these galvos from scratch?


Clearly I still have lots to learn (lots and lots and lots) so I hope you'll bear with me ^.^;

[soforene]

... I hope you'll bear with me...

Whenever I hear that phrase I always think of a Maternity ward.
And breathe ... and breathe ... and PUUUUUUSSSSHHHH !!!!!!!

But welcome to our humble little home on the net anyways ...........

[gottaluvlasers]

hey paraxon!

First off, welcome to PL. youll find it very comfortable here and many people offering help. so never feel like you ask too many questions and never feel like you may ask a "dumb" question.

In plain, basic terms, the layout and process of a laser projector is this-

COMPUTER:

this will have your software control. it doesnt need to be fancy or high end. almost ANY computer will suffice. it could be from the 1980s or it can be a brand new quad core monstrosity. You can get free software such as LaserBoy, Spaghetti or even make your own. Or you can step into a little bit more of a dedicated and "higher end" software like Pangolins Flashback system with quick show.

DAC:

this will be what takes the info from the computer and software and converts it to usable signals for the glavos and lasers to understand. In my above eaxample with the Flashback system, it includes its own hardware DAC. The laser projector will plug into this and be controlled with this hardware/software combo. in the lower end freeware systems, these are controlled (IIRC) by modified sound cards which you do yourself. Others here may comment on that, as i am not 100% sure how it is done.

DMX:

Most people will tell you to use a laser via a computer and software. DMX works "ok" but you get exponentially more control and flexibility via computer. the Flashback system is capable of DMX control but reuires an external DMX controller.

GALVOS:

Your galvos will be wired to a set of Amps that come with them. the amps in trun will be wired to your ILDA connector (DB25 Connector with specific pins for Specific signals) ILDA stands for "International Laser Display Association" and when the term "ILDA Connector" or ILDA compatible is used, it usually means that the projector or signals are wired and used in the standard international format for professional laserists.

ILDA Wiring and standards

LASERS:

Obviously your projector needs some lasers. this is self explnatory.

SAFETY:

Please factor in safety systems in your projector. at the very least, a safety shuttering system. VERY easy to incorporate and a necessity if doing public displays.

Welcome to Lasers my friend! your wallet is officially NOT yours anymore!!! LOL!!!! you may try to fight it, but it will win!

-Marc

[ElektroFreak]

Info on building the above mentioned soundcard DAC can be found here if you're interested:

http://www.photonlexicon.com/forums/...d-DAC-Tutorial

and welcome to the forum!

[ParoXoN]

Hey guys; thanks for the welcome and info!

That soundcard-DAC tutorial was very enlightening; esp on the nature of ILDA control.

For my particular project I've actually got dedicated PWM outputs on my board to use for DAC XD (That's going to be painful to program, I suspect.)

As far as the connectors go, it sounds like an ILDA DB25 connector would be the way to go... So far the only reasonably priced galvo systems I've been able to find are:

SCANECO20 from lasershowparts.com
and
Meierlight thingy

The first appears to be pretty clear that it doesn't sport ILDA connectors and the second isn't very forthcoming

This leads me to two questions:

1. Do you know of any cheap/used galvos (with ILDA connectors or which could be hacked to support them) I could purchase?

2. Supposing I can't find a price-appropriate set of galvos, what kind of performance could high speed servos put out? (Ya, it'll be really, really poor )


Thanks for your help

[Phredy1]

Welcome to the forum!

You might find this thread interesting if you are searching for galvos.

http://www.photonlexicon.com/forums/...y-worth-buying

-Gene

[gottaluvlasers]

1. Do you know of any cheap/used galvos (with ILDA connectors or which could be hacked to support them) I could purchase?

Good timing. I will have a set of used scanpro30ks this week, they still scan perfect, but in all honesty they probably only have about a year of life left in them. they were in a club atmosphere, so they got used quite well. they still are tuned well, scan well, and i can see no problems with them. they will be available this week. PS, amps, scanners and mounting block is obviously incuded with them.

PM me if interested.

-Marc

[dave]

Right now I'm in my final semester of a computer Engineering degree and for my capstone project I thought it would be fun to build a simple (SIMPLE!) laser projector. We're given a basic microcomputer (ARM7TDMI-based) and told to interface it with something.

Nice! A ARM should have plenty of grunt even for a fairly complex laser application. Keep us all informed with your progress!

[ParoXoN]

@dave:
I'll do my best to keep everyone posted with the (probably very painful) progress of my project XD
I think most of you will find it extremely ghetto ^.^;;

@gottaluvlasers:
PM sent XD

@Phredy1:
Thanks for the link! There are so many useful posts on this board @.@

[buffo]

Welcome to PhotonLexicon, ParaXon! Sounds like you've got an interesting project in the works... I think you need to back up a step or two though, before you make any purchases.

As far as the connectors go, it sounds like an ILDA DB25 connector would be the way to go.

Well, the "ILDA connector" is nothing more than a standard DB-25 connector (otherwise known as a parallel port connector) that has been wired with certain signals to control a projector. Most of the signals on the connector are analog, but a few of them (the shutter, for one) are TTL signals. Nevertheless, there's nothing forcing you to use the ILDA connector, apart from being compatible with other controllers. You can always wire your own cabling if you'd prefer.

So far the only reasonably priced galvo systems I've been able to find are:

SCANECO20 from lasershowparts.com
and
Meierlight thingy

The first appears to be pretty clear that it doesn't sport ILDA connectors and the second isn't very forthcoming

Whoops! Ok - let's back up a second. You have a conceptual error here. *None* of the galvos on the market today support ILDA connectors.

The ILDA connector is designed to carry signals from the controller to the projector case only. Once you get inside the projector, all the wiring is point-to-point.

Everything inside the projector housing has to be wired to the ILDA connector. That includes the galvos, the modulation inputs on the lasers, the shutter control input, and any other hardware inside the box. All of this is internal projector wiring. And since you're basically building your own projector (much like many people here have done), you will be hooking up all that yourself. (If you purchase a completed projector at retail, then all you do is connect your controller to the ILDA connector on the projector with a DB-25 cable and you're off to the races.)

The galvo amps *usually* have differential inputs. That is, there is an X+ and an X- input on the X amp, and a Y+ and Y- input on the Y amp. There is also a signal ground connection, which can be used for single-ended operation. (This is not recommended, both because you lose your noise rejection capability, and because the size of the scanned image will be drastically reduced, because the signal intensity will be lower.)

The standard convention is to wire the X+ signal to pin # 1 of the ILDA connector, and X- to pin 14. Likewise, the Y+ signal is on pin # 2, and Y- is on pin 15. If you wire the connector on your projector this way, then you can connect the projector to any commercial laser show controller and it will be able to talk to the galvos.

Here is a list of the standard signals on the ILDA connector, and their location (pinout).

1. Do you know of any cheap/used galvos (with ILDA connectors or which could be hacked to support them) I could purchase?

The Scaneco20 galvos you linked to are an excellent first choice for a starter set of scanners. They're not capable of true 30,000 points per second, but they can still move fast enough for you to create fans, tunnels, beam effects, simple graphics, and limited text. Complex graphics can also be scanned, but they will flicker slightly.

what kind of performance could high speed servos put out? (Ya, it'll be really, really poor )

In a word? Lousy. In two words: Really lousy! Stay away from servos and stepper motors - they just don't have the speed you need. And besides, a good set of high speed servo's will end up costing almost as much as the ScanEco20's. You'll be better off with a proper set of scanners anyway.

Edit: Just noticed Marc's set of used ScanPro30's above. Those would be nice units, even if they are a little tired. They're faster than the Scaneco20's, so you can run complex graphics with them with little to no flicker. If you can get them at a good price, you'll probably be happier with those. (Even though Marc mentioned that they don't have a lot of life left in them, they'll surely last long enough for you to finish this project - and them some! And afterwards, if you find you've been bitten by the laser bug and want to stay in this hobby, you can always upgrade.)

Keep asking questions... You're on the right track, but you want to have a really good grasp of what you're trying to accomplish before you start spending your money. We can help you with that, assuming that we also understand what you're trying to do. From what I've read so far, I'm unclear as to whether the goal of your project is simply the hardware interface between the computer and the projector, or if you also need to write your own control software.

The interfacing part is easy - all you need is a sound card and a correction amp to properly condition the signals. Then you'll need to build the projector, but if you stick with a monochrome green projector, all you're talking about is a laser and a set of scanners. Pretty easy to wire together, and the optical alignment is a piece of cake. (Note that this assumes you'll be running a modern OS on the microcomputer, and using off-the-shelf or freeware laser show software to send laser frame data to the sound card.) In this case, you're looking at a 2 to 3 week project, tops.

However, if you're talking about writing your own control software from scratch and sending it through the sound card, then this project just got a lot harder. Because in addition to doing everything above, you also have to learn a lot about the ILDA file format, how it interprets frame data, and how to output points at a consistent rate to keep the image stable. Then you need to write, debug, and test the software. That's beyond my ability to assist you, but we do have some programmers here that can probably help. Still, if this project is do at the end of the semester, it will be a tall order to accomplish everything in time...

Adam