Topic: guidance for beginner

[johannesgj]

hello
we are a local electronics group trying to get into laser projecting. we understand the outer parts and the results, plus the way the images are packed and so forth.
i am studying electro engineering so basics of that should be ok to.
what we dont get is where to start.

can anyone help us with some guidance here ?
maybe some special topics on the motors/electronics/etc that is being used so we can get into the initial phase.
we have a sponsor in the form of our local youthhouse.

any help to get us started is greatly appreciated!

ps. if we start building a monochrome is it then hard to after that mod it into an rgb?
kind regards johannes gårdsted jørgensen

[James]

Hello johannes!

Welcome to the LaserBoy Forum!

Fortunately for us (laserists) there are things called scanning galvanometers!

These are electro-magnetic devices, similar to DC motors; but they are specifically designed to move tiny mirrors to deflect laser beams. In other words, they are made to do exactly what we need!

They usually come in pairs. One deflects in the X dimension and the other deflects in Y. The result is that they can be used to draw images; much like what you see on an oscilloscope.

Once you have a pair of scanners, then you need at least one laser. This laser should have some sort of modulation. Either it can be turned on and off electronically (TTL modulation) or it can be set to any brightness between off and full on with a varying control voltage (analog modulation).

If you want to have more than one color, you will need more than one laser. Typically, lasers are red, green, blue and violet.

The beams are combined into one beam with the use of special mirrors called dichroic filters. These are mirrors that only reflect from some wavelength up and pass through anything below or the other way around ~ reflect some wavelength and pass everything above.

The colors of light are measured in wavelength in nano-meters.

Red diodes are like 660 to 635nm. Green DPSS lasers are 532nm. Blue DPSS is 473nm and BluRay diodes (violet) are 405nm.

If you have three colors, like red, green and blue (or violet), other colors come as a result of mixing these three. If your lasers have only TTL modulation (on or off) then you can only get 7 different colors.

red
yellow (red + green)
green
cyan (green + blue or violet)
blue (or violet)
magenta (blue or violet + red)
white (red + green + blue or violet)

The quality of these colors will depend completely on the relative brightness of each laser.

On the other hand, if all of your lasers are analog modulated, you can get just about every color you can see by blending various amounts of each of the primary colors.

Yes it is quite possible to start with only one laser and add the other colors later, as long as you leave room in your construction to do so.

Once you have a laser projector, then you need a way to make signals to control it.

That is what LaserBoy is all about!  

You can use a slightly modified multi-channel sound card. LaserBoy lets you create full color laser vector art and it converts that art into a multi-channel wave. When you play the wave, you get the signals that make the show!

To do full color laser projection, you need at least 5 independant control signals. These signals must all be perfectly aligned in time; {X, Y, red, green, blue}.

Please feel free to ask as many questions as you like. Post pictures of your progress.

I'm sure there are others on this forum who would be glad to help you too!

Forum member, Alfa Romeo has some great pictures in his gallery!

http://akrobiz.com/laserboy/forum/index.php?action=profile;u=38;sa=mgallery

Looking forward to seeing what you come up with.

James.  

[johannesgj]

thanks for overwhelmingly welcoming reply 

i feel more secure on the possibilities of an actual outcome now!

Fortunately for us (laserists) there are things called scanning galvanometers!

i had seen these mirror motors in the pictures of different builds. but the difference between the use of two motors contra one didnt hit me until i saw that there apparently is a price difference between using one motor that makes x and y, and using one motor for x and one for y.
i came to the conclusion that the difference probably lies in cost of making those two fit inside the same box and thereby some costly optimization.
which means that i am now in the understanding that the overall difference between one and two motors is not quality but space. is that correct?

is there any general categories of price/quality that can outline the motors? this would make it easier to make a decission on which to buy.
and ive seen that some of them come with some kind of controller in the kit. is this needed or can one connect the motor to the overall controlling engine of the projector which leeds to the next question.

the data in form of waves come from the computer through a soundcard that suplies a number of outputs. and in the end a motor controller steers the motor and something strange (analog modulator) the laser.
what is between the output of the soundcard and the lasers/motor.

and about analog modulator, dont waste your time on explaining ill just look it up myself

well again thanks for your first rely!
and i will definitly post info on my build here!!!
btw. can i post fragments of this conversation on my site http://ibeams.org
ill of course (as i allready do) guide people onwards to this wonderfull place.

[johannesgj]

and just another small question

can you roughly outline the categories of parts and the cost of a medium(dont know yet what this defines) laser projector.

if else ill manage

again thanks

[BlinkenLights]

the "motors" are commonly called "galvos" and there has to be 2 different galvos to make  an image.. 1 galvo can only make a line..

here is a great pic

[BlinkenLights]

the sound card has a few channels
1 channel controls the up down galvo
1 channel controls the right left galvo
1 channel controls how bright the red laser will be
1 channel controls how bright the green laser will be
1 channel controls how bright the blue laser will be

other channels can control other things as well but lets start with that

here is some info that is a bit outdated but will help
http://elm-chan.org/works/vlp/report_e.html
http://www.laserfx.com/Works/Works3S.html

[BlinkenLights]

a simple laser scanner consists of the following parts.

1 or more lasers that can be modulated (aka a signal can control how bright it is)
a PAIR of galvo's (scanning galvanometers)
special glass mirrors for mixing the colors together (dicromatic lenses or "dicro's")
some sort of base plate to mount it all on
something to control the lasers and galvos (the sound card)

[James]

Yes. you can post information from here anywhere you want.

There are two galvos because each one can only move the beam in one dimension. One is to move the beam horizontally. The other is to move it vertically. This is exactly like the X and Y inputs on an oscilloscope.

You need two independent signals from the sound card to control these devices; one for X and one for Y.

The lasers that you get will have some kind of modulation control input. If you get analog modulated lasers, they take a voltage from zero (fully off) to +5 volts (fully on). Anything in between will be proportionally dimmer.

You will also need a signal for each color.

So, if you have a pair of scanners and three lasers you will need 5 signals from the sound card. X, Y, red, green, blue.

A sound card was made to drive speakers. Speakers can not take a constant DC voltage. So sound cards are DC decoupled with capacitors at the output of each channel of the DAC. The modification that you need to do is to get the signals from the sound card before they go through the decoupling capacitors. Once you have that, you will see that it is all positive voltage. It is well above the zero volt line. So you need a special correction amplifier to add a bit of negative voltage with the signals to bring them down to center around the zero volt line. You also need a bit of gain to amplify the voltage up to where it is enough to control the laser projector. Remember, color modulation goes from zero to +5 volts.

Also, if you think ahead for the future, you might want to get a 7.1 souround sound card. This will give you 8 channels. So you can use them for { X, Y, r, g, b, (not used), right audio, left audio } and have stereo sound with your shows!

James.  

[BlinkenLights]

redundancy FTW

[drlava]

Here are some categories of parts and cost estimate:


Sound card DAC: $25-$50
X&Y galvos: $250
Green laser: $150
AL Baseplate: $20-$50

for starters and then to go RGB:
Dichros and mounts: $100-$150
Blu Ray laser: $60-120
Red Laser-$60-$120

and then to make it nice:
shutter: $30
DZ blanking correction board: $55
Enclosure: $50-$250
Poly Wheel/Gratings and pick-off shutter: $??

[James]

Why would anyone need a "DZ blanking correction board" ?

This is done with sample shifting!

James. 

[drlava]

even at 48kpps of a sound card DAC, the ideal adjustment lies in between points on mine.  the blanking board takes care of this.  Also (unrelated to his purpose) blue dpss has different off times and on times and the board can correct for that.

[James]

I guess I'm spoiled. I have a PCAOM! 

James. 

[johannesgj]

thanks again for the replys!
it is always nice to hit a forum where people arent to stressed to talk with beginners

there is a few things i still dont get.
the control comes in form of wawe from the computer and then drives through different channels the galvos and the laser(s)

what i dont get is what kind of driverboards that takes the control from the soundcard and controls the galvo and laser.

i would think that there would be need for two driverboards one for the laser and the galvo.

what is the cost for these driverboards?
are they (for the lasers) so indiviual that they only work with few kinds of lasers each driver?
do they (driver board for galvo and laser) need external powersource?

ive heard something about red lasers not having enough lumens to get seen.
what is the thing about pbs connecting two reds to make a more visible beam?

again thanks!!!
this is more and more fealing like a nice project.

by the way if you guys want to know here is a little background on my reaching out for laser projector project.

me and a friend got a connection to the local youthhouse which is interested in supporting electronic projects. they have a stash of money because they have been support economically in years on the electronics front without having anybody with any projects.
so we had been welcomed with open arms both socially and economically.
the use of this projector would foremost be to showcase it at the norberg festival for electronic geeks and music in northern sweden where we both use to be every year. check here http://www.norbergfestival.com/

[James]

A complete set of scanners can be purchased as one unit. This would include two galvos with mirrors, a mount to hold them together at exactly the correct orientation and a pair of scanner amplifiers to drive them. Modern galvos are "closed-loop" devices. That means that the galvo and the amp are designed to work together. The amp drives the galvo and the galvo tells the amp where it is. This make for a very accurate system.

A laser that is all put together for this kind of use will come with either an analog or a TTL modulation input.

So, all you need is a (modified) sound card and a correction amp. There are threads on this forum about how to make a correction amp. I would be glad to help you with any more questions.

James.