Building My First RGB Projector (Opinions?)

[DJ DoubleBass]

First I'd like to say thank you to the creators of this excellent forum. There's a wealth of knowledge, experience, and friendship that's apparent all over the place. Very cool (wish I knew about SELEM before it was too late)

At first I was thinking of purchasing a projector....something like this:

http://cgi.ebay.com/220mw-RGB-DMX512...d=p3286.c0.m14

Then I discovered this forum and have decided to build my own RGB Projector. (after hours and hours of reading) I figured that I can get better quality that way, and/or if anything breaks, I can fix it. (and it's a VERY cool hobby....and expensive I know)

My first projector doesn't need to be a power house, but it needs to be respectable. I'm still shady on a few details. This is what I know:

I'd like 30K projectors, which typically include the heads themselves, the scanner amps, cables and a power supply. Something like this:

http://cgi.ebay.com/SCANLSP-30-30k-S...d=p3286.c0.m14

Red Laser diode Something like this:

http://cgi.ebay.com/300mW-650nm-Red-...d=p3286.c0.m14

Green Laser diode Something like this:

http://cgi.ebay.com/150mW-industrial...d=p3286.c0.m14

Blue Laser diode Something like this:

http://cgi.ebay.com/150mW-405nm-Blue...d=p3286.c0.m14

Drivers for each (I was thinking of drlava's flexmod1's)

http://www.photonlexicon.com/forums/...ead.php?t=4612

I was toying with the idea of doubling up on the blue ray's because I understand that they tend to be dull. So could I somehow parallel them with drlava's Flexmod1's?

If so how would they be wired?

I know that they could be combined via a cube.

I know that I'll need a set of Dichros, one to pass green reflect red, one to pass green and red then reflect blue.

I know that I'll need a Dac and software, (which I understand makes a substantial difference) and was thinking of going with Pangolin's FB3.

Building materials will be an aluminum case to dissipate heat, respectable heat sinks placed over each diode, and probably some TEC just to keep things cool. (possibly a separate level for the lasers so that the other electronics can be fanned and not blow on the lasers)

This is where I'm stuck....power supply for the TEC, and the TEC itself. Could I piggyback the power on something's powersupply?

Placement, One fan blowing in, one blowing out maybe?

Anyone have any recommendations on some quality fans?

Also, blanking.....I've read so much that my head hurts, and it's been hard figuring out exactly how to make this happen. I've seen where some people add a 3rd Galvo, and I understand that there are other methods, but will the FB3 DAC from Pangolin blank the setup that I've mentioned for an example?

Is it the DAC that can create blanking?

Perhaps there's an existing thread that I haven't found that can explain how to create blanking? (I understand what it does, I just don't understand how to make it happen with hardware)

Something else, connections:

Computer with software, connected to DAC via USB, connected to....I guess an ILDA breakout board via a printer/ILDA cable?,

I know that the galvo heads connect to the amps, which are connected to the power supply...and the lasers to the drivers, then is it the drivers that are connected to the DAC?


Thanks for anyone's time willing to help me.

I'm off to grab some lunch

[Heavyen]

Blanking is done through modulation on laser driver board. Signal comes from DAC over ILDA connection (intensity/blanking pins: 3 and 16). If im correct, 3rd galvo was needed for blanking in case of gas lasers which arent able to turn on and off so quickly.

For fans I suggest u to use positive pressure inside projector, so only fans blowing in, or at least more fans blowing in than blowing out. That will keep dust out of ur projector. Of course, u should put dust filters on ventilators.

[buffo]

Hi DJ DoubleBass! Welcome to PhotonLexicon.

It's a damn shame that you missed SELEM. It was right in your backyard! Still, stay active here in the forums and with luck there will be another event soon that you'll be able to attend. (Though it might not be quite as convenient as SELEM would have been.)

As for your question about blanking, Heavyen is right - most solid state laser modules are modulated directly by the driver. And many people here use the Flexmod driver that drlava sells. Scanner blanking is much slower, and is normally only used when direct modulation is not possible. (For large ion lasers, another option is to use a PCAOM, but this is quite a bit more expensive, and it also loses nearly 20% of the beam power.)

If you're looking for information about TEC's, I suggest you contact MechEng3 here on PL. He's also in North Carolina, and I'm sure he can suggest several solutions that will work well.

Your understanding of the connections is pretty good. Basically the controller does most of the work for you. It connects to the PC (often via USB) and converts the digital data from the PC to a bunch of analog signals which are sent to the projector via the 25-pin ILDA cable. In the projector, those analog signals are sent to the inputs on the scanner amps and the modulation inputs on the drivers for the lasers.

Your idea to use a blu-ray diode for blue is a good way to save money, but understand that it's not really blue - it's more like the violet color of a black light. It's very hard for the eye to see, which means it's not very good for beam work. (It does work reasonably well for graphics, however.) And yes, like most diodes, blu-rays are polarized, so you can combine two beams together using a polarizing beam-splitting cube in reverse. You can wire the diodes in parallel with a 1 ohm resistor in front of each of them and power them from a single driver if you want.

What do you want to do with your projector? Is this something you plan on using for your own enjoyment in your basement, or are you looking to use it commercially? (Commercial use opens you up to a whole host of legal requirements that would probably be difficult for you to deal with right now.)

Adam

[DJ DoubleBass]

Thanks for all of the information! I thought Buffo would chime in after seeing him be all helpful all over the forum.

Sorry for all of the questions:

So the DAC controls modulation, but what actually powers the Driver for the laser? A power supply keeping in mind the specs for the Flexmod Driver? (input: 5-12VDC) ?

Does the 5-12VDC for the Flexmod make a difference in the performance of the laser?;

Or does it just power the driver/laser, then is otherwise power adjustable via the driver?

After signal from the computer to the DAC via USB, would I need an ILDA Breakout board to be able to connect to the signals that are "sent to the inputs on the scanner amps and the modulation inputs on the drivers for the lasers?"

Again, sorry for so many questions. I tend to ask a lot of them so that way I know exactly how to approach something and have plenty of confidence in the work.

What do you want to do with your projector? Is this something you plan on using for your own enjoyment in your basement, or are you looking to use it commercially? (Commercial use opens you up to a whole host of legal requirements that would probably be difficult for you to deal with right now.)

For now it'll be just for home use. I've read a respectable amount about applying for variances via the FDA's website, and understand that when I DO decide to incorporate it into some shows, (I'm a DJ and a drummer) that there's a lot of precautions that must be met, as well as paperwork to fill out, to insure a safe, and legal show.

Did you hear about what happened in Russia? Apperently 30 people's eyes where hurt from an unsafe lasershow. Most with permanent damage....

http://www.laserist.org/forums/showthread.php?t=195

That's epic....anyway long story short, I understand the seriousness of lasers.

[CRFultz]

You can wire the diodes in parallel with a 1 ohm resistor in front of each of them and power them from a single driver if you want.

Adam

I was wondering how people did this in the past....what is the purpose of the 1 ohm resistor in series with each diode? I'm planning on using flexmods on a red and the violet dual diode setup. Should i set my current the same for a single diode application?

Chuck

I found a post from DRLava that answered this...thanks anyway.

"Hi, yes you can run many diodes of the same type from one driver, just stay within the current limitations of the driver (5A max)

Each diode is slightly different so to even out the current draw between the diodes when they are in parallel, you should put a (thick) metal film resistor in series with each diode. This is true for driving parallel diodes no matter which driver you use.

Let's say you are making a super red and want to use as many red diodes as possible, and you want the max current to be 350mA to each diode, and the lasing threshold is 75mA. Choose a resistor so that it drops about 10% of the diode voltage at the idle current, or 0.3V at 75mA: 4 ohms. Then calculate its voltage drop and power disipation at full power: 4 ohms*350mA = 1.4V; 1.4V*350mA= 0.49W

So, for an array of open can diodes you should use 4 ohm, 3/4 or 1W resistors in series with each diode. Maximum number of diodes on one driver is 5A/350mA = 14 diodes.

Minimum power supply voltage for the driver would be 3V (diode voltage) + 1.4V (resistor voltage) + 2.5V (Driver requirement when delivering 5A) = 6.9V

Finally, your diodes should be of the same make and model, and thermally coupled so they stay close to the same temperature. They should be connected to the same size heatsink block and with the same length and type of wire."
__________________

[buffo]

So the DAC controls modulation, but what actually powers the Driver for the laser? A power supply keeping in mind the specs for the Flexmod Driver? (input: 5-12VDC) ?

Really sorry for the late reply - been super busy these past several days trying to sort out my vehicle issues.

Yes - you normally have at least one 12V power supply inside the projector to power the drivers for the different lasers. (And also to power other things like fans, the shutter, and indicating lights.) Some people have individual power supplies for each laser, but there's nothing stopping you from using a single, central supply for everything. (Well, except for the scanners, as they normally have their own power supply that produces +24 volts and - 24 volts.)

Does the 5-12VDC for the Flexmod make a difference in the performance of the laser?

No. If you feed the Flexmod more than 5 volts it will simply get a little warm, but the operation of the laser diode will be the same. Just don't feed them more than 12 volts and you'll be fine.

After signal from the computer to the DAC via USB, would I need an ILDA Breakout board to be able to connect to the signals that are "sent to the inputs on the scanner amps and the modulation inputs on the drivers for the lasers?"

An ILDA breakout board makes it much easier to do, but you don't need one, strictly speaking. You could wire your own DB 25 connector on the back of the projector if you wanted to. (That's how my projector is wired - only because I built it before DZ started selling his ILDA breakout boards.)

The cable between the DAC and the projector is a 25-pin ILDA cable. At the projector you need to pick up the signal from pins 1 and 14 and send them to the X scanner amp. Then pins 2 and 15 go to the Y scanner amp, pin 13 goes to your shutter control, pin 5 goes to the modulation input for the red laser driver, pin 6 goes to the modulation input for the green laser driver, and pin 7 goes to the modulation input for the blue laser driver. All grounds get connected to pin 25.

That's a lot of wires to solder to a small DB-25 connector, which is why the ILDA breakout board makes things so easy.

Again, sorry for so many questions. I tend to ask a lot of them so that way I know exactly how to approach something and have plenty of confidence in the work.

Keep asking questions. For every question you ask, there are 10 people lurking (but not posting) who are wondering about the exact same thing you are.

For now it'll be just for home use. I've read a respectable amount about applying for variances via the FDA's website, and understand that when I DO decide to incorporate it into some shows, (I'm a DJ and a drummer) that there's a lot of precautions that must be met, as well as paperwork to fill out, to insure a safe, and legal show.

Cool. We can help you with that process, when you're ready to take that next step.

Did you hear about what happened in Russia? Apperently 30 people's eyes where hurt from an unsafe lasershow.

Yeah, last summer. Here's more information on the incident, courtesy of the ILDA website. Long story short, they were using PULSED lasers, which are 10's of thousands of times more dangerous than continuous wave lasers.

what is the purpose of the 1 ohm resistor in series with each diode?

You basically have the idea. The 1 ohm resistor offers more resistance than the diode itself does when operating. (Once a diode starts conducting, current can rise very rapidly with just a small increase in forward voltage.) The extra resistance in the circuit helps to balance the current draw among the diodes in parallel.

Adam

[DJ DoubleBass]

AWESOME!

Thanks for the reply. Everything is much brighter now. (light was shined)

Sorry about your vehicle. It's only when things go wrong with one when you realize how much you may need it.

Guess what....more questions

When I build this projector, would it be cost effective to just go ahead and build around the idea that it may be used commercially?

I ask this because after continuing to read around, I found that a switch with a key is required for example. Maybe it would save time if I coordinate the plans of the scanner around including one? (as opposed to having to disassemble one later to install one)

SHUTTER

"pin 13 goes to your shutter control,"

What is the shutter?

Thanks again

[allthatwhichis]

I would build with the idea of being as safe as possible; then when you want to go commercial you will already be equipted.

[buffo]

When I build this projector, would it be cost effective to just go ahead and build around the idea that it may be used commercially?

Yes. I would suggest that you build it with this in mind. It doesn't add much in the way of cost or complexity, and it adds some important safety features that are useful even if you don't ever plan to use it for a commercial show.

I found that a switch with a key is required for example. Maybe it would save time if I coordinate the plans of the scanner around including one?

Absolutely. You will also want to include a shutter, an emission indicator (basically a light that comes on when the lasers are powered up), a power-on delay (that is, the lasers don't come on until 5-10 seconds after power is applied), and a remote kill switch that the operator can use to stop all laser output immediately if something goes wrong.

What is the shutter?

It's a safety device that blocks the beam so it can't exit the projector. It can be something as simple as a solenoid that pulls out of the beam path when energized, and returns to block the beam path (via a spring) when de-energized. It's controlled by your DAC, but should also be able to be closed by hitting the remote kill switch.

Many people use a GM-20 actuator, since they are quiet, have a built-in spring return, and they actuate very fast. This thread has more information on various shutter devices. (You need to be sure whatever device you select has a spring-return mechanism, otherwise it won't be legal for commercial use.)

Adam

[DJ DoubleBass]

Thanks again

This forum absolutely rocks

I'm getting more and more clear on everything with each step/question.

So now that I've decided to just plan around every spec of legality with this projector, is there a thread that lists details of all of the requirements for the projector to be legal? (ready for a variance request)

So far:

*Lock and key

*Kill switch ran to the operator

*Spring loaded shutter that's activated (de-energized) when the kill switch is engaged

*Emission indicator (basically a light that comes on when the lasers are powered up)

*Power-on delay (that is, the lasers don't come on until 5-10 seconds after power is applied)