What's the cheapest you can go?

I want to spend as little cash as possible and get some sort of scanner that I can control with a microcontroller or computer. I guess my plan right now is to use my red labbie, and a green module combined with a microcontroller/audio source, and a transistor to each module. I have a couple dichros so I could make an RGY laser. However, the problem comes with the actual scanning part. I dissected a couple of old CD drives our IT guy gave me and got those little focusing things that tilt to either side, I'm pretty sure using 2 digital pins on an arduino with PWM and flipping the polarity of each should let me control the tilty thing pretty easily, and give me some sort of rudimentary XY setup with 2 of them. However, I don't want to go through all this annoyance and trouble if I can just spend a few bucks and get some really crappy galvos or a used setup or something. Plus, I still have to get the mirrors. So should I go ahead and try to make this, or is there some other way that I can get a rudimentary scanner cheaply? (No need to draw pictures on the wall or anything with the laser).

Thanks,
will

Galvo's these days are CHHEEAAPPP.

The amount of effort it'd take to DIY something, you could get some cheap galvo's which would work so much better.

I made one once using the spindle drive from a CD player, there is a magnet disc on the bottom of the shaft and a coil arrangement that looks like a flower under the magnet.

Cut the traces leading to the coils and solder wires to the traces leading to the coils.

Glue a FS mirror on top of the hub, and then use whatever you want to drive the coils.

I used a 555 and a flip flop followed by buffers, the faster the clock pulses were the faster the mirror rocked back and forth.

I also recall seeing a coil pair with mirrors on them on ebay for under $20 before.

Things said:

Galvo's these days are CHHEEAAPPP.

The amount of effort it'd take to DIY something, you could get some cheap galvo's which would work so much better.

Click to expand...

I'm sorry, I'm sure you get this all the time and I'm sure there are links all over the place and right when I stop looking I'll find them, but where do you buy them? All I can find are $2000+ super crazy galvos and these ~$40 ebay galvos I don't really trust. Also, how do you control a galvo? Do you hook a DAC right up to it, or do you get some kind of driver and use serial? Most of the kits I see in this section appear to have amps and stuff to control it, but where are these bought, and how are they used?

photonaholic said:

I made one once using the spindle drive from a CD player, there is a magnet disc on the bottom of the shaft and a coil arrangement that looks like a flower under the magnet.

Cut the traces leading to the coils and solder wires to the traces leading to the coils.

Glue a FS mirror on top of the hub, and then use whatever you want to drive the coils.

I used a 555 and a flip flop followed by buffers, the faster the clock pulses were the faster the mirror rocked back and forth.

I also recall seeing a coil pair with mirrors on them on ebay for under $20 before.

Click to expand...

I have 3 of these things where it's some coils and a lens suspended between 2 neodymium magnets. They rock side to side and move up and down.
will

Will, some of the most rewarding educational experiences I can remember was experimenting, trying new things and thinking outside the box.

If the stuff you have is surplus junk, then tinker around, it's fun.

Have you ever built any of the basic electronic "building blocks" like op amps and flip flops?

Just to shed some light on tinkering... I was all of 14 years old or so when I picked up an old black and white TV at the dump, Brought it home and turned it on.

The picture was just snow and distortion, no wonder the owner chucked it.

I took off the back and severed the wires feeding the big yoke coils in the stem of the picture tube, I hooked the horizontal sweep to the left channel speaker output of my boom box, and the vertical sweep coil to the right. (or the other way around) so the varying sine wave fed the coils.

I had a TV spiro controlled by music with only 10 minutes labor and four wires.

Later on, I made a simple oscillator to make the horizontal do a "line sweep" and fed signals to the vertical sweep coil, presto a crude oscilloscope.

The point I'm trying to make here is, give it a try, the same principals I just described could be implemented into a cool scanner.

^thanks, I never really got the chance to do simple stuff, at first I had a little kit that had a few transistors and stuff. For the next couple years it was all theorectical, then recently I actually started building things seriously again. So I never got a change to make any logic gates or anything, it was all software which is why I like the arduino. But I'm still gonna use the CD things, I just don't wanna spend a bunch of time trying to make it into a scanner that will function too poorly.

Want some simple breadboard schematics Will??

I have them.

photonaholic said:

Want some simple breadboard schematics Will??

I have them.

Click to expand...

For what?
But sure- I guess you can never have too many schematics

thanks,
will

eBay, you can get a 20K set for around $120 nowadays. lasershowparts.com may have some too.

ossumguywill said:

For what?
But sure- I guess you can never have too many schematics

thanks,
will

Click to expand...

to drive your project, I thought you wanted those mirrors to move??

For a quick start you could get a Projector from pf-lighting.com. they're real bargain.

(but in 2 weeks earliest, China has New Lunar Year now...)

photonaholic said:

to drive your project, I thought you wanted those mirrors to move??

Click to expand...

Sure. Schematics are always a good thing to have

Xer0 said:

For a quick start you could get a Projector from pf-lighting.com. they're real bargain.

(but in 2 weeks earliest, China has New Lunar Year now...)

Click to expand...

thanks, I'll look into it.

will

Just go to ebay and search for "galvo". Here is a 20K set for $110.
laser show galvo scanner CW20K Scanning galvanometer - eBay (item 120504497356 end time Feb-08-10 00:53:48 PST)

You can't go much cheaper than that and you certainly can't build anything that will come even close to the quality of the output of these.

Use an red DVD laser diode for your laser with an Aixiz module for a holder. For a green, you can get one of those 50-80mw Aixiz lab modules for $65. You can even use a blu-ray diode to make it RGB.

For a DAC, a sound card will work or you can spend more and get something like Norm's DAC for $200. If you don't care much about quality, you can get an iShow Dac that comes with software for $130.

Of course, you can use my software (Spaghetti) for $50 and it will work with just about every DAC except Pangolin FB3. There are other software packages out there as well (some free, some expensive).

Anyway, those are some of your options.

Don't just go for what is cheapest before you figure out what you want to ultimately do with it. If you just want to tinker then definitely go cheapest. if you think you might make a hobby out of it then you should figure out what will do what you need and then save up and buy it once instead of buying cheap and then upgrading and upgrading. It's cheaper to save and buy once than to buy cheap and keep upgrading.

Good luck!

update:
using arduino PWM and an NPN transistor, I was able to make it tilt up and down pretty accurately. Now I need to get an op amp I think, because using the transistor I can only make it tilt one way. Using a roughly 29% PWM with one polarity makes it go all the way down and 100% with the other polarity pushes it up. So I need to make a program that switches polarity of 2 PWM pins (I hope that works) so I can flip-flop and get a full range of motion. I also need a better amp than a transistor that will work with both polarities.

will

On most galvo amps, they just use audio amplifier chips. Since the frequencies we are working with are very close to audio frequency, they work perfectly if you can get some.

Things said:

On most galvo amps, they just use audio amplifier chips. Since the frequencies we are working with are very close to audio frequency, they work perfectly if you can get some.

Click to expand...

OK, but how do galvos even work in terms of movement? How is it controlled, what does each wire do? If there is 0 input voltage, does it go to the middle, or if there's negative or positive voltages it goes to the side?

will