Polar coordinate laser oscilloscope

[buffo]

now my interest is peaked on discovering if an XY galvo set can reproduce this effect or not.

You can do *anything* with galvos. Only problem is that the cost of the galvos goes way up as you try to run the pattern faster and faster. So really the decision will be - is it worth the expense of a galvo solution to gain the added effects that galvos can deliver (beyond what you can do with just the voice coil and rotary mirror...)

Voice coils can have damn fast response time if driven and loaded properly. In fact, there are plans floating around the internet that show you how to use a pair of old speakers to build a set of galvos. Of course, you won't have any feedback, so they're open loop only. But for abstract patterns, open loop galvos are ideal anyway.

Eh - it's an interesting question. Not sure how fast the galvos would have to be to mimic everything you can do with your current voice coil setup, but you should be able to find out once you get your analog synth circuit assembled. Then too, there are things you can do with galvos that you'd never do with the single voice coil and spinning mirror, so that's something to consider.

Good luck with the project! Keep us informed of your progress...

Adam

[curtcoffee]

Hi All,

I was able to reproduce the same effect using the 15kpps SCANECO15 from aijii on eBay and an amplitude modulated SIN, COSIN oscillator to feed the X & Y galvo amp.
Will post photos of my set-up after the holidays.

Best Regards,
Curt

[curtcoffee]

Hi All,

Well the holidays are over so I’m posting my XY to polar oscilloscope setup and result pictures. You should find a thumbnail photo gallery here: http://www.musicalaser.com/XYpolar.htm Click on the photos to get a larger view.
Equipment used: 15kpps SCANECO15 XY galvo, amp and power supply from aijii on eBay for <$300, the guts of a 5mW laser pointer stuck in a finned heat sink controlled by a DIY TTL MOSFET switching low side power, and my version of the simple printer port 2 channel 8 bit DAC found on Norm’s homemade laser show page http://24.202.226.190:81/LaserShow.htm , ( my thanks to Norm ! ) all mounted on a two piece stack of rigid PVC foam board. Everything is scaled for +/-8 degrees. Images were projected onto my lab door 9 feet away. I think the pictures tell the tale that this low cost XY galvo system can easily produce a musical polar display oscilloscope using a sincos oscillator with VGAs, as well, using a cheap PC simple text and simple vector graphics can be made. To generate the ild graphics I used the freeware software on Norm’s webpage and the open source Monkey tools. I need to update the DAC and cosin schematics and PCB to Rev B as a few mods were needed to get the signals scaled correctly, should have that done next week. Looking at the waveforms generated by the function generator, there seems to be some type of optical calibration needed to get the inside points together. Perhaps it’s the galvo axis vs the mirror reflective plane that are mis-aligned.

On a different subject, does anybody know what the legalities are about projecting images like your URL on public and or private surfaces without prior permission ?
I'm guessing it's a no no. How about a snow bank?

You can buy a 12" x 18" (or so) first surface mirror at most any stainglass shop for about $20, mirrored side has protective plastic coating. Cut it like regular glass, use a diamond file to make it as thin as you want.

Well its been fun playing with this stuff ! I'm thinking about home brewing some galvos and PID amp next.

Best regards,
Curt