Pages: [1]   Go Down
Author Topic: X/Y Reflector for a mirror  (Read 1073 times)
0 Members and 1 Guest are viewing this topic.
Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 47
Posts: 2892
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I have always wanted to make a speaker type X/Y reflector to display Lissajous (sp?) figures on my walls, ceiling. The mechanical part is easy, a front silvered mirror, 2 speakers, some rubberbands (suspension), some glue and other odd bits 'necessary'. The drivers (speakers) will need amplification and I have some LM386's and the design skill to provide PWM low-pass filters for the mirror drivers (necessary for smooth circles) but I haven't the math skills necessary for 'Uno' generated art. Displaying sine waves in two axis is easy a linear ramp provides a means to move the mirror right to left and any other input will display (for the period of the ramp) the portion of the other input that is co-incident with the ramp. This is a brief description of an oscilloscope or a vector display... useful only at audio and low ultrasonic frequencies because of the physics of the drivers ( amplifiers chosen and required filters and driver motors 'speakers' are poor drivers at high frequencies for a number of reasons)).
Any Idea's???

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Central MN, USA
Online Online
Tesla Member
***
Karma: 73
Posts: 7198
Phi_prompt, phi_interfaces, phi-2 shields, phi-panels
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

It will sound like DTMF dial tone all the time, a bit maddening. That is what you hear when you mix say 1000 with 500Hz waves to get some Lissajous graph of a figure 8. The keys are frequency, AND phase angle. You will have to consider how to adjust phase angles. I think lower frequency might be better.
Logged


Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 47
Posts: 2892
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Yes I know but it isn't meant to generate sound... I estimate that less that 100 mW total will be required and all moving parts will be mechanically isolated... Simple enough to do with some foam and silicone based adhesives... Further If both the x and y axes are fed the same linear ramp signal, properly phased... the Red Laser diode could be pulsed on/off for a 'Vector Display'[ device... great for displaying text too...
Red is the only even half safe color to use, Blue will cause permanent eye damage at 1/2 mW power levels and green isn't much better, VERY dangerous because of the possibility of 'accidental' reflection. Initially small speakers will be the 'linear' drivers for a proof of concept design... Later well???


Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Central MN, USA
Online Online
Tesla Member
***
Karma: 73
Posts: 7198
Phi_prompt, phi_interfaces, phi-2 shields, phi-panels
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I think it's a good concept. You could initially drive the speakers with DC just to see how the offset changes the laser dot with different voltages and then use modulated voltage to write letters, similar to a laser spirograph.
Logged


Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 47
Posts: 2892
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Yes, John I know... I built my first oscilloscope in 1962 from an OLD 5" Philco Tv... all the early television sets were electrostatic deflection and fairly easy to re-work. One of my earliest thoughts on this subject was to use it for Bio-Feedback experimentation. The Uno is fast enough to do rudimentary DSP on the available electroencephalographic information. That exercise is in the future however. I have a great deal to learn yet about the Uno before such a project is "do-able". I do however hope to get a workable display of gross electroencephalographic information and display it on a Graphic LCD. I am VERY WELL AWARE of the issues presented... First is the possibility of shock or other damage to me (the test subject) the device will be battery powered and communicate information optically (easier that dealing with radio issues) Second the human body is in a constant 60Hz electromagnetic and electrostatic fields... simple notch filters for that and an absolute rolloff @ 40 Hz should allow me to see what is going on. I am also very interested in Galvanic Skin Resistance measurements for Bio-Feedback applications for my own use... The Uno and an SD Card adapter will make me a great data logger. I don't think that I will publish any of those findings as they are Very DANGEROUS to make and I wouldn't want to encourage others to do the same thing. I have several years experience in repairing medical electronics equipment... So I do have some background...

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Phoenix, Arizona USA
Offline Offline
Faraday Member
**
Karma: 40
Posts: 5581
Where's the beer?
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I estimate that less that 100 mW total will be required and all moving parts will be mechanically isolated... Simple enough to do with some foam and silicone based adhesives... Further If both the x and y axes are fed the same linear ramp signal, properly phased... the Red Laser diode could be pulsed on/off for a 'Vector Display'[ device... great for displaying text too...

Can't be done in the manner you are thinking of, namely you are trying to build an "open-loop" system, with no feedback on position.

If you want to go beyond simple lissajous (sp?) figures, and be able to project text/graphics using vector means, you need the feedback. You also need speed, and a fair amount of deflection. That means the device holding the mirror has to fast and lightweight, with little mass. The more mass it has, the more overshoot/undershoot becomes an issue (resulting in poor repeatability, and "ringing" on corners or other sharp position transitions).

What you ultimately want to look into is what is called a "laser galvanometer"; these devices work real similar to an analog meter movement - except they have a form of position feedback. They are very fast, and very lightweight (well, the moving parts are). Position feedback is generally done via capacitive sensing, or optical reflection.

People have built homemade galvos, but it isn't simple; from what I've gathered, it can be a very painstaking and frustrating process - but the reward can be worth it in the end.

Again, attempting to do this with speaker drivers or other methods without feedback will yield little more than a curiosity (not to say that such a device can't generate interesting, fun, and beautiful patterns; it most certainly can!); if you want to go beyond that level, you need the feedback capability (if you can in some way incorporate such a method in a speaker driver mechanism, you'll be halfway there - unfortunately, such linear drivers of that nature tend to have waaaay more mass than you want for such use).
Logged

I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 47
Posts: 2892
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Wow thank you for the input. The device was only meant as a curiosity. If I wanted accuracy I would strip most of the speaker cone out and drive it from a well damped source, one that can deal with the effects of the return (Back EMF) current from the coil and probably use that information for positioning feedback, much the same as most real motor speed controllers so...
No this was only meant as a "Wow Golly Gee...." kinda thing. I have always been fascinated with those "Text Scanning Displays" where the text seems to float...
I have one of those Sure Electronics 3208 8 X 8 X 4 matrix displays as well but I thought that the "Writing on the Wall" concept was really irresistible.
A simple "well defined" ramp generator and a means of switching the laser (0.5 mW ONLY) on and off... sure looked like a great way to use up a week or so... I'm a Retired Auld Phart, probably with too much time on my hands. The "Raster Scanner" has been around for a long time... Television before the digital age. The only real issue is 'distorting' the ramp to 'paint' on "non-linear" surfaces. This almost comes into the area of
 "Self Correcting Optics" . If nothing else it is an interesting and thought provoking area of endeavor.
I bought my first transistor at age 14, I grew up fixing vacuum tube equipment. I remember the First real digital watch and the first calculator too. I will be 66 in June, Fat and Sassy and lovin the life I lead and I have a Long memory...
And I talk too much.

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Pages: [1]   Go Up
Jump to: