In Progress Project, Laser Squiggle Generator: V2

[Nemo222]

HI all,

For my first PL thread I would like to share with you one of my current laser projects, the second version of my laser squiggle generator. A visualizer that runs on incoming audio signals. It can be used anywhere there is a deficiency in squiggles.
http://youtu.be/g5N-9qTjn9o

I had the idea for my original squiggle generator many years ago. I had the resources and time to put it together about a year ago. I recently had an extra laser laying around with no home and decided to make V2.

The laser is the super cheep RGB brick, 500mw TTL. I was actually very happy with this laser for quite a long time up until the blue diode in it packed it in. Kinda upset about that but it looks like I can get a replacement diode for about 30$ from OPT lasers, or I may just disassemble the host a pop a new diode in. Haven't decided yet. Luckily I filmed this video the day before the blue died. The scanning is accomplished by two hard drive read write arm galvos which are fed the same raw audio as the speakers. The entire thing is housed inside an old micro hi-fi stereo system which serves two purposes, It hosts the amplifier to drive the galvos and serves as a case for everything. The original one used a 100mw green laser pen diode from a 25$ laser pointer who's case broke. The new one uses the RGB brick hooked up to a micro-controller to control color changes, a start-up delay and a no signal timeout. The micro controller receives signal from a rudimentary beat detector circuit which is simply a band-pass filter with a comparator on the output. A signal between 18 and 80hz with sufficient amplitude triggers the micro-controller which changes the color to a random new one.

The new one is going in a new stereo case with new hard drive galvos, the video shows my old squiggle generator with a hole cut in the back where I am firing the new laser in along the same beam path. I got the beat detector working and wanted to see how it would squiggle.

Some pictures of building the original to show you whats going on inside. And the sort of squiggles it generates.


I appreciate your comments and suggestions for V2.

[JasonB]

Well that's pretty cool. I would be careful with where you point your squiggle generator (and it looks you are are!) , since you are basically doing 'open loop' position control. I noticed that scan angle changes quite a bit, so it concerns me that it could be easy to catch a beam in the eye. 500mW is serious power. Smart move to point it at the ceiling and keep your distance. [End of safety lecture]

I enjoying seeing how we re-purpose basic hardware to throw around photons... and in your case, three different wavelengths. Its cool to use what you have on hand to create something unique!

So you are using hard drive motors for your galvos, are you driving them with an audio amplifier ?
Also, on your video I see you prototyped a circuit that you are using to drive your laser colors... Nice work.... What is the function of the USB cable, though ? How are you turning your RGB on and off ? Did you cook up an analog circuit to do that (I see an 8-pin chip that could be an op-amp, or maybe a comparator?) or is the PC modulating the color via USB ?

[TechJunkie]

Great idea, and looks cool too!

micro-controller to control color changes, a start-up delay and a no signal timeout. The micro controller receives signal from a rudimentary beat detector circuit which is simply a band-pass filter with a comparator on the output. A signal between 18 and 80hz with sufficient amplitude triggers the micro-controller which changes the color to a random new one.

Can you elaborate on this please. ^^ Schematic, parts list, ect? Thank you.

[Nemo222]

Well that's pretty cool. I would be careful with where you point your squiggle generator (and it looks you are are!) , since you are basically doing 'open loop' position control. I noticed that scan angle changes quite a bit, so it concerns me that it could be easy to catch a beam in the eye. 500mW is serious power. Smart move to point it at the ceiling and keep your distance. [End of safety lecture]

So you are using hard drive motors for your galvos, are you driving them with an audio amplifier ?
Also, on your video I see you prototyped a circuit that you are using to drive your laser colors... Nice work.... What is the function of the USB cable, though ? How are you turning your RGB on and off ? Did you cook up an analog circuit to do that (I see an 8-pin chip that could be an op-amp, or maybe a comparator?) or is the PC modulating the color via USB ?

I agree with the safety lecture. This is ALWAYS pointed above eye level. When there is no audio signal there is no moment of the beam and I have no second to second control over where it is and how fast it is moving. It does throw out some cool looking beams, but they are not the reason it exists.

The scanning is accomplished by two hard drive read write arm galvos which are fed the same raw audio as the speakers. The entire thing is housed inside an old micro hi-fi stereo system which serves two purposes, It hosts the amplifier to drive the galvos and serves as a case for everything.

The micro controller receives signal from a rudimentary beat detector circuit which is simply a band-pass filter with a comparator on the output

So in summary
Yes,
Usb cable is just powering the beat detector circuit.
The micro controller handles the color switching with the TTL signals.
The beat detector is a dual channel op-amp doing analog beat detection.

Can you elaborate on this please. ^^ Schematic, parts list, ect? Thank you.

The beat detector is just a bog standard first order bandpass filter. High pass over 18hz, amplifier stage, low pass under 90 something Hz, comparator output.
For some reason the output signal on this particular circuit is inverted, 5V when there is no beat dropping to about 1V when there is a beat. Conveniently the micro controller doesn't care and its all taken care of in software.
The schematic is here.

[Galvonaut]

Welcome to PL Nemo

Nice project - my first was based on a hard drive and PC fan

Keith

[JasonB]

Thats a great idea using bandpass filters to modulate your laser colors. I also used filters to drive spot lights to audio signals for part of my senior design project which is shown in the left hand picture in post #4 of this thread:

http://www.photonlexicon.com/forums/...ght=blast+past

Instead of using a microcontroller like you did I wired the positive signal from each of the bandpass filter outputs into a schmidt trigger ('beat detector') which in turn drove solid state relays to run 100 Watt floodlights. I think I had 8 channels, then used a PIC to drive the the lights in a 'chase mode'.... Looking back I think it was a good thing I only had a 5mW HeNe tube that I salvaged out of some photo equipment otherwise I literally would have probably been dangerous back then..... My squiggle detector was a piece of mirror glued to a speaker...

The most gratifying part of the floodlight project was when I was running those 8 floods in my bedroom one Friday night in the house we rented on the outskirts of campus (while a student) a stranger wandered into our house, walked right into my bedroom, and said 'Oh, sorry, I thought there was a party going on in there' ...Heh heh