Post by thread:[OT] Galvanometers

I know this is kinda off topic, but since this is the only hardware/software/everything list that i know of, i'll post it here.... A couple of years ago, i saw a demonstration of a DSP from Analog Devices, wich displayed a rotating logo on a oscilloscope in X/Y mode. I have lately been thinking about doing the same thing, but with a laser instead... It could be fun to make a rotating (digitaly) clock display (like the opengl screensavers that come with WinNT 4.0), that was blown up on the wall... I was planning on using some galvanometers (if i can find some cheap) (Someone here mentioned that there was some in a videodisc player???) And a laser diode, for the light thing.. So my questions is: 1. Anyone got any experience with such an implementation? 2. Where do one get hold of galvanometers? 3. How fast can one turn a laser led on/off? 4. See number 1. :) I know that it must be some kind of vectorised graphics engine in a DSP (i don't think a PIC is fast enough for this one). But besides this i haven't got any clues as to how i should attack this little challenge... - Thomas

On Sun, 28 Dec 1997 22:09:03 +0100 =?ISO-8859-1?Q?Thomas_M=F8rch?= <spam_OUToz2afoTakeThisOuTPOST8.TELE.DK> writes: >It >could be fun to make a rotating (digitaly) clock display (like the >opengl >screensavers that come with WinNT 4.0), that was blown up on the >wall... > > I was planning on using some galvanometers (if i can find some cheap) >(Someone here mentioned that there was some in a videodisc player???) >And a >laser diode, for the light thing.. > 2. Where do one get hold of galvanometers? Look for "swing motors" instead. The pen in some types of chart recorders (anyone remenber chart recorders) such as those used for medical analysis was driven by one. Most newer hard drives use one (and a lot of feedback) to move the heads. The hard drive motor would need a spring added to give it some direction of where it should stay. Also I've heard of removing the paper cone from a loudspeaker and attaching a mirror instead. Driving these devices with current rather than voltage may work better. > 3. How fast can one turn a laser led on/off? Very fast. Several MHz are possible. But, using a standard module with the power control built in it may not operate faster than a few Hz without modifying something. > >I know that it must be some kind of vectorised graphics engine in a >DSP (i >don't think a PIC is fast enough for this one). But besides this i >haven't >got any clues as to how i should attack this little challenge... > Early video arcade games used a vector scan monitor and obtained effects like this using the 8-bit Von Neuman processors (Z80, 6502) that were the style of the time. So the AD demonstration may actually be using little processing power, but still making an impressive demonstration. The process generally involves computing a matrix based on the angle position of the display, then multiplying the x,y coordinates of each point to be displayed by it to get the screen coordinates of the rotated image. So a fair amount of multiplication and addition (DSP chips are good at that) but very little trigonometry. After the screen coordinates of each point have been computed, then it's just a matter of computing the x and y slopes between the ones that are to be connected with lines, and driving the display. Rather than tackling the laser end right away, try getting it running on an oscilloscope first. Or, rather than trying to compute a rotating display, try making a simple straight one first.

I saw something about this on a laser faq. There were also a few pages I found about students doing this at uni. I unfortunately no longer have the links, but try looking for a laser FAQ. Thomas M¿rch wrote: {Quote hidden}> I know this is kinda off topic, but since this is the only > hardware/software/everything list that i know of, i'll post it here.... > > A couple of years ago, i saw a demonstration of a DSP from Analog Devices, > wich displayed a rotating logo on a oscilloscope in X/Y mode. I have lately > been thinking about doing the same thing, but with a laser instead... It > could be fun to make a rotating (digitaly) clock display (like the opengl > screensavers that come with WinNT 4.0), that was blown up on the wall... > > I was planning on using some galvanometers (if i can find some cheap) > (Someone here mentioned that there was some in a videodisc player???) And a > laser diode, for the light thing.. > So my questions is: > > 1. Anyone got any experience with such an implementation? > 2. Where do one get hold of galvanometers? > 3. How fast can one turn a laser led on/off? > 4. See number 1. :) > > I know that it must be some kind of vectorised graphics engine in a DSP (i > don't think a PIC is fast enough for this one). But besides this i haven't > got any clues as to how i should attack this little challenge... > > - Thomas

On Sun, 28 Dec 1997 22:09:03 +0100, you wrote: {Quote hidden}> I know this is kinda off topic, but since this is the only >hardware/software/everything list that i know of, i'll post it here.... > > A couple of years ago, i saw a demonstration of a DSP from Analog Devices, >wich displayed a rotating logo on a oscilloscope in X/Y mode. I have lately >been thinking about doing the same thing, but with a laser instead... It >could be fun to make a rotating (digitaly) clock display (like the opengl >screensavers that come with WinNT 4.0), that was blown up on the wall... > > I was planning on using some galvanometers (if i can find some cheap) >(Someone here mentioned that there was some in a videodisc player???) And a >laser diode, for the light thing.. > So my questions is: > > 1. Anyone got any experience with such an implementation? > 2. Where do one get hold of galvanometers? > 3. How fast can one turn a laser led on/off? > 4. See number 1. :) > >I know that it must be some kind of vectorised graphics engine in a DSP (i >don't think a PIC is fast enough for this one). But besides this i haven't >got any clues as to how i should attack this little challenge... > >- Thomas If you can find an OLD Philips top-loading laservision player, these have a HeNe laser and a nice pair of voice-coil controlled mirrors. These players can sometimes be found at hamfests etc. very cheap. ____ ____ _/ L_/ Mike Harrison / White Wing Logic / .....wwlKILLspam@spam@netcomuk.co.uk _/ L_/ _/ W_/ Hardware & Software design / PCB Design / Consultancy _/ W_/ /_W_/ Industrial / Computer Peripherals / Hazardous Area /_W_/

At 01:07 AM 12/29/97 GMT, you wrote: >If you can find an OLD Philips top-loading laservision player, these >have a HeNe laser and a nice pair of voice-coil controlled mirrors. >These players can sometimes be found at hamfests etc. very cheap. I've played with these quite a bit. The mirrors are incredibly slow. Also, the power supply for the HeNe can't be switched on-off very quickly. They are real fun for light shows, but not much good for vector displays. The Pioneer disk players have similar problems. Cheers, Bob http://www.bobblick.com/