Simplify [++]

[buffo]

Thank you! Thank you! I'll be here all week... Try the veal!

Seriously though, I've gotten toasted a few times and then tried to tinker with stuff. Every once in a while it works out OK, but more often than not I end up breaking something.

As for getting rid of the amps - bad idea. They perform a vital function. (comparing the signal to the position feedback and modifying the drive current accordingly) Likewise, you need some sort of controller (D/A converter) to send the data from the PC (which is a digital device) to the scanner amps (which are analog). At the very least, this means a sound card. But call it what you want - it's still a controller. So that's another piece of hardware you need.

The computer you can do without - so long as you have some sort of storage medium on the controller that can hold the frame and show data. But you still need to load that content onto the storage, so you're still talking about a computer at some point...

Granted, it's a lot of pieces to cobble together to make a show work, but each piece performs a vital function. Take any one away, and you don't have a working system anymore. You could combine them into a single device, but all the functions still need to be there. And I don't see how integrating everything into a single black box is going to benefit anyone...

Adam

[steve-o]

Ok, I'll try the veal.
I'm getting to the point now (finally) that I'm thinking of all the pieces inbetween the PC and the galvo amps. Is there a discussion or block diagram on PL that shows it all? I'm unclear as to where the printer port from the PC (DB25 cable) is going to; say, a 'Norm's DAC' and can control RGB blanking and X/Y galvo amp inputs..

[DZ]

PC to galvos - inotherwords, download prog

Good point. And actually this can be simplified. Especially since most DAC's are USB or Ethernet connected now. When I get time, I plan on throwing my QM2K into my projector permenantly. So it will require just a simple ethernet connection from any computer with the pangolin software loaded. I think that would make it just about as easy as it gets. My existing ILDA input port will become an ILDA out to a slave projector. As far as interlock loop and etc. I don't typically share info like this until I have a tried and true, proof of concept working model, which is only half done at this point but I see no reason why it should work. Since there will only be ethernet going to the projector, I'd really rather not have ANOTHER cable for safety. So instead, I'm going to tap into the UTP Cat5 cable. Which has 8 conductors, 4 of which are in use for ethernet and the other 4 are unused. So, final design will have a small box that will have 2 ethernet connectors on it, one connects to the computer and the other connects to the projector. The box will have a key switch, emergency off and shutter control. Without the box, the projector just plain doesn't work.

[allthatwhichis]

Hey, can you make two so I can be the beta tester.

[carmangary]

I'm going to put my galvos, DAC, scanner amps, etc, into a big cardboard box and cut some holes in it so I can access the keyboard and to let the laser shine out. That'll do it.

[buffo]

I'm unclear as to where the printer port from the PC (DB25 cable) is going to; say, a 'Norm's DAC' and can control RGB blanking and X/Y galvo amp inputs..

I think you're getting caught up because a parallel DAC uses the same 25-pin connector that the ILDA standard does, and that's where you're trying to skip a step. Let me break it down for you.

It all starts with the computer. You have the frame files stored there in digital form. Somehow you need to convert that digital data to a pair of analog waveforms that will be sent to the scanner amps. (one for x and one for y) Then the scanner amps will monitor the feedback signal from the galvos to make sure that their position matches the one specified in the analog input waveform for each axis. (For simplicity's sake I'm ignoring the blanking signals, along with the shutter and other control signals that are also sent to the projector.)

Anyway, to get this digital data into analog form is the job of the laser controller. (Many people call it a DAC, because that's one of it's functions.) Now, there are many different controllers. Norms laser show DAC is one example. It uses the parallel port on the PC to receive the digital information, and it outputs an analog signal that gets sent to the galvos. But here is where the confusion starts: Both the input and the output on Norm's laser show DAC are DB-25 connectors! That's because Norms controller uses the parallel port (which has 25 pins and carries digital data) for input, and it also supports the ILDA standard for output (which also happens to use a 25-pin connector, but it carries ANALOG signals.)

Now, if you were to use a different controller - say, the EasyLase USB DAC or the Pangolin Flashback 3 controller - then you wouldn't be using the computer's parallel port to send data to the controller. Instead, you'd be using a USB cable to send the digital information to the controller. But you'd still have that ILDA connector on the output; that carries the analog signals that will be fed to your projector (and to the scanner amps inside).

Likewise, if you went with a Pangolin QM-2000 board, or a Ryia PCI controller, the only connection between your PC and your controller would be the card edge connector, because the controller would be plugged directly into the computer's motherboard. But even so, you've still got a 25-pin ILDA connector on the back for the analog output from the board.

Now, some people are using sound cards as controllers. (Laserboy, Uclinux laser, etc) But obviously, sound cards don't have 25-pin connectors on the back. So you need to wire an adapter from the sound card outputs to a DB-25 connector if you want to have an ILDA-standard output. Each pin on the ILDA connector is devoted to a specific signal. (If you're curious, here's a link to the pinout description for the ILDA output connector.)

Anyway, no matter which controller you have, so long as the output is wired to the ILDA standard, that means that you can plug in anyone's ILDA-standard projector and it will work. That's the whole point behind using the 25-pin connector for wiring your projector to your controller. It allows for flexibility. It may not be all that useful for a hobbyist, because it's unlikely that we'd have multiple projectors. But for someone in the business, it's a great time saver. They can use the same controller to run a small solid state projector (that might only be rated for 500 mw of output) as well as a huge krypton/argon mixed gas rig that might be rated for 10 watts. The cabling to the projector is the same. (Well, excluding the power and cooling requirements of the laser of course!)

The important thing to remember is that there are three key pieces of equipment in the chain. You start with a computer (or some other digital device that can store and output frame-data) Then you need a controller (DAC) to convert those digital signals to analog. Finally, you need the scanner amps to amplify those analog signals and send them to the galvos. (The amps also implement the feedback signal from the galvo position sensor.)

So you have two sets of wires connecting these three main parts. The first connection is from the PC to the controller. This can be a PCI slot, a USB cable, an ethernet cable, or a parallel cable. But in any case, it's a DIGITAL link. The second connection is between the controller and the projector (or, more accurately, the guts inside the projector). This link is normally a 25-pin cable that has been wired to the ILDA standard. It is an ANALOG link. Note that you don't have to use the ILDA standard if you don't want to. You could run individual wires from the output of the controller to your components inside your projector. The ILDA standard just makes it easy for different controllers to control the same projector (and vice versa.)

Now, if you think about it, you'll see why you can't connect your projector directly to the parallel port on your computer. The projector is an analog device, but the computer is a digital one. There are no analog signals on a computer's parallel port.

In fact, the only analog outputs that a compute has are the sound card and the video card. (Which is why some people have opted to write software to use the sound card as a controller.) While in theory you could also use a video card as a controller, they're more expensive than sound cards, and the higher bandwidth of a video card would be wasted because the scanners can't work with high speed signals.

Adam

[Banthai]

just a quick post about this ....

couple of years ago at the ILDA meetup .... Dirk from Medialas was demoing a pair of small Galvos that had the amps buit inside the galvo body i think all that was required was a 12v and analogue input from the dac to each galvo


all the best ... Karl

[steve-o]

Thanks Y'all that cleared it up