|Laser shows are cool, so why not build my own? There are a lot possibilities for building a laser scanner. It's all about speed and accuracy. Some people use galvo meters, some power device others use speakers. My first attempt was to use the computer speakers and control this with my soundcard & a text-to-wave-file-converter. But unfortunately this will only create lissajous figures. So that's why the second approach will be a galvo meter...|
Although the aim for this project was not a quick laser system, it's was more for fun, understanding steppers a little better. I also attached a webcam for future use. Well first back to the laser display system. It consists of 2 cheap steppers, with mirrors, arduino board and pc connection. Press the mouse somewhere in the black box and the laser will point in that direcition, projected on a wall. So this works, altough both speed & resolution are very low. I tried to play around with the arduino servo library: write() & writeMicroseconds() commands, but it doesn't really make a difference. This propably due to the cheap AD-converter in the servo.
Also making a circle on the wall, the output is very course.
CD-player & lens
Hard disk & lens
|Why not use 4 speakers
||Chez's best system:
||MY FIRST MODEL!
You can download my 1D speaker system movie here. This is not what I have in mind, so up to the galvo's...
Some time later, I found out, how a simple speaker system could work. It's well written by NothingLabs.com, which created also a connection to display Twitter messages. Basically the speaker hardware system is completely replaced by very simple electronics. The negative DC signal is completely removed, so the speaker cone works like a spring & the coil will move the cone by a bigger or smaller current. In this way it's possible to make other graphs then the lissalous figures.
So this means, the coils will also constantly dissipate energy and everything will warm-up. Secondly this is not a closed-loop system. It could be seen as using a (open-loop) stepper instead of a faster & more compact (closed-loop) servo motor. Another negative side effect, is the sounds it produces.
This is not what I had in mind, so let's figure out, how the real XY galvo scanners work...
Here you see some DIY closed-loop galvo meters:
- Capacitive sensors, like Chan
- Optical sensors, like Norm
- Magnetic sensor, like Francois's setup
Results & learnings so far:
There are also some options for software control. Some (expansive) XY scanners use serial connection, others LPT or the sound card. If you are using LPT there is a nice inpout32.dll created by Logix4u.net which works under WIN NT4, WIN2000, WINXP.
For my first approach a simple wave file editor is sufficient (speaker system). I found a nice wave file description @ ccrma.stanford.edu, see picture. Then just create a converter which reads numbers from text file (16bits stereo) and convert this with an adjustable sample rate into a wave file.
The second approach will be a little harder. Options so far:
In this case, the amplifier & closed-loop system needs to be developed.