[HN Gopher] Final Project: Vector Laser Projector (2019)
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Final Project: Vector Laser Projector (2019)
Author : codezero
Score : 42 points
Date : 2021-04-08 17:34 UTC (5 hours ago)
(HTM) web link (people.ece.cornell.edu)
(TXT) w3m dump (people.ece.cornell.edu)
| dreamcompiler wrote:
| This is an impressive project, but it uses an FPGA which is
| completely unnecessary. With modern processors there's no reason
| you can't do all the requisite computations in software, provided
| you use realtime programming techniques. I know this because I
| built a laser vector projector in the 80s driven by 8-bit
| processors of that era. It didn't use SVG as input; that
| definitely needs more cycles, but with a modern processor it
| should be easy. Galvo motors are S-L-O-W compared to CPUs.
| codezero wrote:
| In fairness, the course was a course in FPGAs, so it was part
| of the requirement, but I take your point. I happened to find
| the project when looking for some FPGA resources and thought it
| was pretty awesome :)
| ChuckMcM wrote:
| This is a fun project! I think they might to work a bit on their
| linearity :-).
|
| Some laser pointer sources allow for gate control (turning them
| on and off with a logic signal) which might help.
|
| Steve Ciarcia had a project[1] in BYTE for doing a vector display
| on an oscilloscope which ported well to lasers.
|
| [1] https://archive.org/details/byte-
| magazine-1976-11/page/n79/m...
| codezero wrote:
| When I got to the point about powering the laser I was (only a
| little) hoping they would use a mechanical shutter of some
| sort, I bet that would work fine enough as long as it doesn't
| cycle on and off _toooo fast_.
| portillo wrote:
| Reminds me of OpenLASE: - https://github.com/marcan/openlase -
| https://www.youtube.com/watch?v=hoWCNKhZCbk
| Animats wrote:
| Of course the drive circuit is overheating. An LF353 op-amp is
| not a power device. Continuous total power dissipation for that
| thing is 500 mW. Needs an output power transistor with more
| current handling capacity.
|
| Since there's already an op-amp with feedback, that op-amp can be
| used to take the feedback signal from after the power transistor,
| so you'll still have closed-loop following and the output voltage
| will track the input properly. One power transistor in a TO-220
| case (about US$0.59 each) per channel should give you about 10 or
| more watts, rather than 500mW. That ought to be enough.
|
| The Art of Electronics is good for designing things like this.
| And LTSpice helps.
| codezero wrote:
| In my physics degree we took an electronics course based off
| that book and I still crack it open for reference once in a
| while.
| neetdeth wrote:
| Regarding the distortion observed in the output, I believe this
| is due to the inherent physical properties of the galvo system,
| specifically that the actuators have momentum. A more
| sophisticated controller would either slow down the beam when
| entering a corner, or deliberately overshoot and add connecting
| moves where the beam is turned off.
|
| There's also evidence of some ringing in the output, which might
| indicate an underdamped PID controller in the servo itself.
| news_to_me wrote:
| This is awesome! I knew something like galvo motors must exist
| but I never looked deeply into it. I'm going to have to use
| something like this to build a better automatic cat laser.
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