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I'm Building a DIY-HDD XY-Scanner

diachi

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wummi said:
thanks for the advice, for now i'm powering them at 0.5W max.

the problem is, the arms dont return to zero fast/precise enough. i guess rubberbands just dont cut it :)

how do real galvos work this?

has someone built somethin like i did here?
im thinking of giving each coil a DC offset, maybe 2V, an modulate from 1V to 3V with 2 being the zero point. anyone think that will work ?!
I think this is how real galvos work, as they always spring back to the middle. The amount of movement from them is tiny though, it's more like rotational vibrations.


-Adam
 



kendon

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hi @all

i build a similar scanner myself just yesterday ;)

i started the project a while ago, but got bored when it was to align the mirrors. a few days ago i put a nice order an dx for some led-projects, and threw a few lasers in. then i got excited, went to conrad (german radioshack-like shop) and bought a 5mw pointer to start building some effects (couldn't wait for the "real" lasers, and also i don't want to burn my eyes testing something, so i test with the small one and use the big one for the real show). so yesterday i began with a simple liquid sky on a pc fan, but it sucks with the <5mw red pointer. then is started to rip the two harddisks apart, but i gave up when i noticed that it is way too hard to cut harddisk-cases with a manual small saw. after discovering that i was out of hotglue i started cleaning up, only to find two sticks of hotglue under my closet ;)

30 mins later the scanner was done, and it ended in a pretty simple and straightforward design i think. i will post pictures and videos later this evening, when i have made some good ones...

in the mean time can someone explain how the speed test works? all i see is more or less of a line going from left to right, what can you tell from this and can you tell it by looking at the (no offense) crappy videos?

and also wummy, what song or sound did you use in the video? i didn't hear anything, but actually i don't trust ubuntu with .mov...
 

wummi

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kendon said:
and also wummy, what song or sound did you use in the video? i didn't hear anything, but actually i don't trust ubuntu with .mov...
there is only faint sound coming from the harddisks, and its a random DnB internet radio channel.

also, german greeting from vienna :)
 

kendon

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ah sh*t. i'm too dumb to use this forum, and after youtube "processed" my video there's nothing to see anymore. i will post some pics here.

and i will try this heathcliff tool, sounds promising!
 

wummi

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i fixed the heads further with springs... its much more accurate now

here's a quick movie of a few shapes i made with the software

http://www.youtube.com/watch?v=7p8K6ac6nhs

my main problem now is the DC cutoff from the soundcard... i might get a usb one and build a real "soundcard DAC"

any reccomendations on USB soundcards?
 

DTMF

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@ kendon  it was just a test of how fast the 555 timer would make a line and stop where i want'd it to . this project is kinda hard if you limit your self to just  spare cheap part's .

@wummi the 555 timer/oscillator  can be used in line with your circuit to oscillate the arm's very fast . i find the less volt's i send the arm  the less it slap's back and forth . i have found that diff hdd arm's can take diff voltage . i have 1 that work's great at 9v's  i have no idea why . the reason i used the 555 timer was to make the unit stand alone . kinda like a spiro . when you use cap's of different value's in the timer ciruit   you get different oscillation's   . i used 10 different value's on each timer that you would select with a rotory switch . and 2 pot's on the timer to control the speed of the oscillation the mock up build work'd but i nevr finish'd it  . i built a 4 motor spiro with forword/rev and speed control on all 4 motor's  insted ;D
 

lasersbee

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DTMF said:
@ kendon  it was just a test of how fast the 555 timer would make a line and stop where i want'd it to . this project is kinda hard if you limit your self to just  spare cheap part's .

@wummi the 555 timer/oscillator  can be used in line with your circuit to oscillate the arm's very fast . i find the less volt's i send the arm  the less it slap's back and forth . i have found that diff hdd arm's can take diff voltage . i have 1 that work's great at 9v's  i have no idea why . the reason i used the 555 timer was to make the unit stand alone . kinda like a spiro . when you use cap's of different value's in the timer ciruit   you get different oscillation's   . i used 10 different value's on each timer that you would select with a rotory switch . and 2 pot's on the timer to control the speed of the oscillation the mock up build work'd but i nevr finish'd it  . i built a 4 motor spiro with forword/rev and speed control on all 4 motor's  insted ;D
Just a heads up...

using the 555 in astable mode you could leave a fixed capacitor and change
the value of the timing Resistor instead.... just replace it with a potentiometer (pot) and you will
have infinite adjustment instead of just 10 preselected... as in your circuit.. ;)

Jerry
 

DTMF

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i have replaced the Resistor's with potentiometer's . i also like to use different dischage rate's that,s why i use 10 different capacitor value's. that way i have infinte adjustment of different capacitor value's . it also set up for monostable or astable mode :D
 

lasersbee

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DTMF said:
i have replaced the Resistor's with potentiometer's . i also like to use different dischage rate's that,s why i use 10 different capacitor value's. that way i have infinte adjustment of different capacitor value's . it also set up for monostable or  astable mode  :D
[smiley=tekst-toppie.gif]
 

MarioMaster

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Hey guys, just thought I'd throw in some bits of info since a few people asked how commercial lasershow galvos work - basically they do not have a spring or anything to return the galvo to the center position when powered off.

When my ScanPro 20 set is turned off the galvo mirros rotate freely. They have a position tracking sensor and when power is applied the chip on the driver board detects the current position of the mirrors and the position where they should be, and sends power to the coils until the mirror reaches the correct position
 

wummi

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MarioMaster said:
Hey guys, just thought I'd throw in some bits of info since a few people asked how commercial lasershow galvos work - basically they do not have a spring or anything to return the galvo to the center position when powered off.

When my ScanPro 20 set is turned off the galvo mirros rotate freely. They have a position tracking sensor and when power is applied the chip on the driver board detects the current position of the mirrors and the position where they should be, and sends power to the coils until the mirror reaches the correct position

as i understand there are cheap open loop galvos, that use springs, and better closed loop ones.

what ive read, converting openloop to closedloop increases speed and precision dramatically

i tought about building a simple closed loop circuit for my HDDs, but i think i will sack that and just buld "real" galvos myself

something like these fellas do: http://74.58.33.200:81/FriendGalvos.htm

i plan on using a soundcard dac, i already ordered a cheap usb-soundcard. im gonna modify an audio-amp to suit my needs. so i guess its time for me to build some coils this weekend.. lets see how this works out
 

wummi

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here are some pics of the "final" setup, i just mounted it so some scrap metal. as for now, i can do about 0.8-1Kpps at estimated 8°

on the pictures you can see the springs i mounted.
 

kendon

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so here's the pics, just decode it (_=/), since i'm not allowed to post links...

profile.imageshack.us_user_kendon

i am going to make some more right now, so if there are only four pictures you need to wait a few minutes.

@wummi: how did you stick the cuts to the arm of the hdd? i'm still looking for the best way to mount mirrors to anything, since hotglue is obviously not the real deal...
 

DTMF

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kendon said:
so here's the pics, just decode it (_=/), since i'm not allowed to post links...

profile.imageshack.us_user_kendon

i am going to make some more right now, so if there are only four pictures you need to wait a few minutes.

@wummi: how did you stick the cuts to the arm of the hdd? [highlight]i'm still looking for the best way to mount mirrors to anything, since hotglue is obviously not the real deal...
[/highlight]

i use j/b weld work's real good as long as the surface is good and clean
 




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