First scanner build (eventual tutorial)

paulzimm said:

Galvo Questions: My galvos are quoted at 20 degrees optical deflection @ 20Kpps which is the default setting. For example on the X axis, does that mean at a maximum it can scan 10 degrees left and 10 degrees right for a total of 20 degrees? I tested with a compass and that seems VERY small. Is it really 40 degrees total - 20 degrees each way from center?


To get 20kpps you will need to scan allot smaller than 20 degreese with those scanners. Think more like 10 degrees. If you tried to scan 20kpps @ 20 degreese you would blow up the scanners.

And yes, 20 degrees means 20 MAX not 20 left and 20 right for a total of 40.

ALSO: I notice that one side of the galvo (where the motor/mirrors actually mount) is shorter than the other. When looking from above, it is rectangular in dimension. Through which side should the beam enter - the short or the long side? It may not even matter but I figure I would ask since this is my first set. Please see attached photo... Thanks!

You want the beam to enter from the side, then hit the bottom mirror, then bounce to the top mirror, then exit the front.

Click to expand...

-Brooks

^Untrue. The Spacelas galvos ARE RATED TO 20k@20deg. In other words you can run them all day long at 20k@20deg and they will do just fine. I do it with mine all the time. Also, you will not blow up your galvos by running them at their maximum angle, but you will get distorted imagery if you try to go faster than 20k@20deg. As long as the galvo motors do not get too hot you don't have to worry about them blowing up. KGB is correct that the rating is 20deg total deflection at which the galvos are rated to make 20k, BUT you can go wider if you slow the scan speed down to compensate. I run mine at 15k@~40deg most of the time since I do primarily beam shows. You will hurt the galvos eventually if you try to run them that wide at full speed.

Quick question: For my RRGB rig, do you think I could use this as a beam combiner even though it is not polarized?
Optotronics "Precision" Beam Splitter Cube

I just received it in the mail and after testing, I think it can only be used as a beam splitter. I think I may just have to pony-up and buy the following since it IS polarized, right?
CTlasers.com - Polarizing Beam Cubes

paulzimm said:

Quick question: For my RRGB rig, do you think I could use this as a beam combiner even though it is not polarized?
Optotronics "Precision" Beam Splitter Cube

I just received it in the mail and after testing, I think it can only be used as a beam splitter. I think I may just have to pony-up and buy the following since it IS polarized, right?
CTlasers.com - Polarizing Beam Cubes

Click to expand...

first one will not work for combining, second one will

flecom said:

first one will not work for combining, second one will

Click to expand...

Thanks, I just now ordered the correct one from CT Lasers. I also uploaded a video to demonstrate what the "splitter" is doing: YouTube - Optotronics PBS Cube

do you know for sure that that pointer is polarized? remember if the pointer isnt polarized the PBS will not work as expected

never heard of a "precision" beam splitter... so who knows

ElektroFreak said:

Those specs (or similar) are what most Chinese galvos are built to.. the differential +-2.5v color signals are a bit weird, but it's still a 5V p-p signal.

Click to expand...

I think those values are correct by ilda standard.

Remeber those color signals are differential too, giving a difference of 5 volts between -2.5 and +2.5 volts. This is not very practical to drive most constant current driver circuits, but afaik it does conform to the standards!

Same thing with the X and Y signals, those are -5 to +5 range, totalling 10 volts.

Well for the final setup I am actually using a 2 x LOC red diodes which I know are not polarized.

paulzimm said:

Well for the final setup I am actually using a 2 x LOC red diodes which I know are not polarized.

Click to expand...

I am fairly certain LOC's are polarized

Oh wow, I didn't know that's how PBS cubes work. I thought that the polarization of the laser was done within the cube itself and that the mirror inside would reflect one (polarized) beam while letting the other pass right through. So I guess I would "twist" one of the beams 90 degrees offset from the other by experimentation until it works. No need to respond, I sent CT Lasers an email letting them know I would call first thing Monday morning. I think I will also need to get some XYZ mounts from them as well because I think I am going to have a hell of a time trying to line up all the beams by just using a hot glue gun LOL

By the way, once I make a basic (working) projector I have the feeling that I will probably be upgrading it as time goes on. This is just a start for me, I earn a pretty decent salary (computer programmer) and I can really see myself going totally overboard with this

PBS cubes will pass one polarization and reflect the opposite polarization... so for example reflect H and pass V...

you will have to rotate the diodes for maximum pass/reflect... you can eyeball it or use a power meter if you have access to one

ElektroFreak said:

^Untrue. The Spacelas galvos ARE RATED TO 20k@20deg. In other words you can run them all day long at 20k@20deg and they will do just fine. I do it with mine all the time. Also, you will not blow up your galvos by running them at their maximum angle, but you will get distorted imagery if you try to go faster than 20k@20deg. As long as the galvo motors do not get too hot you don't have to worry about them blowing up. KGB is correct that the rating is 20deg total deflection at which the galvos are rated to make 20k, BUT you can go wider if you slow the scan speed down to compensate. I run mine at 15k@~40deg most of the time since I do primarily beam shows. You will hurt the galvos eventually if you try to run them that wide at full speed.

Click to expand...

I talked with the sales rep at SpaceLas and the faster PT-30K's can do 40 degrees at 25Kpps! I now have my PT-20K's up for sale.

They are unused and I am asking $80 with shipping included within the USA:
FOR SALE: SpaceLas PT-20K max35k [UNUSED]

Just got all the components to my sound card DAC today and I soldered everything together. It's coming together great so far! I used a ribbon cable from an old PC which I intend on connecting to the C-Media sound card when I get that in the mail. Tomorrow I am going up to get some 1/4" aluminum plate cut (16"x20") for the base. Just need a few more things and then I should be done

^Lookin good man!

paulzimm said:

Understood - I really appreciate all the help and advice you guys have been giving me. I plan to share my knowledge with others on this forum and maybe even post a review of my RRGB scanner rig once it is complete.

I contacted the manuafacturer of the galvos asking them if the "signal input" conforms to the current ILDA specification of +/-10V. They actually said it was +/-5V and sent me the following PDF (see attached screenshot) of the specification they use. It is probably outdated. No need to reply, just wanted to tell you what I found. Thanks again!

Click to expand...

Those are differential signals and they are actually +-10V when you take in acount both sides of the connector. When one pin is +5, the other will be -5V. +5 - -5V = 10V. When the pin is -5V the other pin will be +5V. -5V - +5V = -10V. The same math will yield +-5V for the colors. The people sending out emails from the Chinese companies are usually clueless from my experience.

Hello again, I got two of the FlexModP3 drivers in the mail today:
http://hacylon.case.edu/ebay/laser_diode/FlexModP3.php

One driver will be used to power a 445 diode and the other will be used to power two LOC red diodes in series (each LOC will get half the voltage). Now the FlexModP3 driver has a 1.5 volt drop (battery input versus output to LD) and I am currently using a rechargable lead-acid 6 volt battery which at full charge is just around 6.3 volts. I have tested this tonight and it works perfectly for my 445 diode because it keeps the output voltage just under 5 volts when pulling 1 amp. Tomorrow night I will test my two LOC red diodes in series with the other FlexModP3 driver.

Since the laser projector is for home use only, I don't want to always be charging the 6 volt battery and instead want to use an 'industrial grade' power supply like one of these:
5 Volt AC/DC Power Supplies, Low Power, 1 to 70 watts, Chassis and Enclosed

Problem is, almost all of these type of regulated power supplies are 5 volts. Will this work for me at 3.5 volts (5v - 1.5v drop) for my 445? I hear a lot about limiting the current on these forums but not too much about the voltage. Just how important is it that I give my 445 exactly 4.7 volts, and my LOC diodes 2.3 volts?