The laser

In some event and speciality in techno event there is sometime a laser that is part of the lighting system. Some of those laser are very complex, but when you look closely on how it work it is pretty simple.

You will need a laser first, the most common is a green DPSS laser, DON’T forget to check if there is a IR Filter ! DPSS Laser can output many eye-damaging IR Radiation if not filtered out ! If your are new to laser, make sure you read all the risk related to exposing someone to laser radiation.

Let say you know what your doing, you will seek for something like this :

You could also use a laser diode from a blue ray drive and build a simple violet laser:

You have two mirror that move in either vertical orientation or horizontal orientation. You also have a way to turn on and off all laser channel.

Here is how to layout your Mirrors :

I like to think outside the box, normally to control those mirror you will get a very expensive laser controller that in fact is very much a analogic amplifier. So knowing that the computer industries make million of sound card it is probably much cheaper to start with a sound card.
The only problem a sound card has, is it is made to control a speaker and has capacitor that need to be removed. In my case I’ve taken a 20$ USB 5.1 sound card and removed the capacitor from it.
Now when I output a constant square wave the output voltage varies from 1.6V to 2.3v. This is a great starting point!

The next step is to build an audio amplifier that doesn’t output sound but constant current, this was very easy. I’ve chosen the standard TDA2030 but removed all capacitor from the implementation. The result was pretty amazing, I now got a constant current amplifier derived from a sound card! For less than 30$ !

Here is how I’ve setup the TDA2030:

Another plus of using a sound card, is that there is many audio channel. I use the other channel to control the close open state of the laser using a simple transistor.
So the design is very simple :
Front channel left control the mirror horizontaly
Front channel right control the mirror verticaly
Rear channel left control the open state of the green laser
Rear channel right control the open state of the blue laser
Center channel control the open state of the red laser ( not implemented yet )
What fantastic about using a sound card, is from a software point of view, it becoming to be very easy. You can create wave in your c# code and output it directy to the waveout device.