Analog Galvo Driver

I’m trying to build an all analog driver system to drive X-Y scanners for use with some old gas lasers.

Back in the mid-1980s, a group of us junior college geeks enjoyed harvesting HeNes and 60X Argons from Surplus Sam of Southern California. Some of us pointed these lasers through galvos for a then, state of the art, spiro projection setup.

I used to have a system my friend Jeff designed, and I built, using Burr-Brown 4423 Quadrature Oscillators. The 4423 is a neat, but dated chip, which outputs both analog sine and cosine – ideal for an X-Y mirror setup. No DACs needed. It made some beautiful images.

I think my ex-wife got rid of the console system along with a bunch of defunct PCs, because it was built inside a PC chassis.

My searches on the net for "analog driver scanner laser schematics" are not producing the results I want. Many of the hits are for digital to analog systems. I recognize, in this day and age, digital is the way to go. But I’d like to build a complete analog system, again, using the above mentioned Burr-Brown oscillators.

Can anyone point me in the right direction for locating an existing design?
Are there any analog veterans left in this industry?

With simple analog input and analog output, are you not looking for an amplifier of sorts? Something with appropriate input/output Zs and a frequency response tuned for the X range of your galvo speed?

Meatball said:

With simple analog input and analog output, are you not looking for an amplifier of sorts? Something with appropriate input/output Zs and a frequency response tuned for the X range of your galvo speed?

Click to expand...

Of course I am. I'm sorry if that didn't go without saying. My old system was a voltage controlled (VCO) system with pots to limit the min/max voltage and frequencies. I'll want this, again, as the galvos I hook these too may vary.

What about just building your own signal source from scratch, something like this:

After a little more reading... that above circuit probably won't get very high frequencies. There seem to be some decent higher speed designs in this doc though.

I already have a handful of the 4423s. They're a sweet chip, and I have a datasheet... somewhere. :thinking:

The circuit you found is a start. But whatever it is that provides the sine/cosine signal, even if it's a DAC, it's the support circuitry around it that I lack experience in designing. I was hoping this wasn't uncommon, and someone may know of a DIY schematic.

Some things I think I need are controlling the voltage (VOC) and amplification (+/- 10V).

There were 6 knobs on my old system, three for each channel, X & Y. IIRC, the three knobs swept through phase-shift, frequency and amplitude.

EDIT:

datasheet: http://pdf.seekdatasheet.com/442/4423.pdf

pschlosser said:

Of course I am. I'm sorry if that didn't go without saying. My old system was a voltage controlled (VCO) system with pots to limit the min/max voltage and frequencies. I'll want this, again, as the galvos I hook these too may vary.

Click to expand...

Hmm. Well we're just about to spend the next 5 weeks of class on frequency dependent circuits and filters and whatnot. So right now I might have no idea what I'm talking about.

If you need to directly "drive" something, look up the NJM4556AD Op amp. Its used to actually drive loads. It can over power any set of low impedance headphones, and is used in some "transparent" headphone amp designs as the main power stage. It could be useful since it might allow you to keep your design needs approximated to the op-amp.

You could probably control max/min voltage by varying the differential supply to an op-amp. As far as changing the frequency response - are you looking to simply block unnecessary frequencies? Or perhaps maximize gain on the desired ones?

I think PL might have some members that know the exact device you're looking for...

Meatball said:

You could probably control max/min voltage by varying the differential supply to an op-amp. As far as changing the frequency response - are you looking to simply block unnecessary frequencies? Or perhaps maximize gain on the desired ones?

I think PL might have some members that know the exact device you're looking for...

Click to expand...

I have a thread on PL going, too. I've had offers to sell me a system, but the asking price is a bit out there.

I'm not sure I care what chipset I use. I'm just looking for a working design.

What I've done in the past is built a correction amp using a circuit Benm posted, and then feed it the signal source. The correction amp just takes the signal and outputs the differential voltage the galvo driver signal inputs require. It might be as simple as that for your system.

The correction amp should cover the signal amplitude. For affecting the signal frequency, assuming you're using the 4423, the datasheet mentions that you can program the resistor values at pins 3 and 12. Both resistors need to have equal values; so an easy solution for that would be to connect the two pins to a stereo volume control.

All this would only control the speed of the beam going around in a circle. For a spiro type thing you could probably sum the outputs of multiple oscillators; however, that may produce too strong a signal, or too weak depending on state of the various oscillators.

Meatball said:

With simple analog input and analog output, are you not looking for an amplifier of sorts? Something with appropriate input/output Zs and a frequency response tuned for the X range of your galvo speed?

Click to expand...

i want to creat a square with laser show,
but i dont know frequency of galvoes
do you know about this?

I see this is a bit of an old thread but I'm glad parimah bumped it up, didn't see it before! I've been working on an analog console project for well over a year. It's really a modified version of a system that was created in the early 1980's. Here's a sneak peak of some of the functions of the console. I'm about another 2-3 weeks away from having the final product finished.

New analog console is slowly coming to life! - YouTube

Anyway, the sine/cosine generator, or Quadtrature Oscillator, is certainly the most important part of any console. This particular console utilizes 7 individual voltage controlled quadrature oscillators. I've always wanted to play around with the BB4423 but was never able to get my hands on one.

DJZ said:

I see this is a bit of an old thread but I'm glad parimah bumped it up, didn't see it before! I've been working on an analog console project for well over a year. It's really a modified version of a system that was created in the early 1980's. Here's a sneak peak of some of the functions of the console. I'm about another 2-3 weeks away from having the final product finished.

New analog console is slowly coming to life! - YouTube

Anyway, the sine/cosine generator, or Quadtrature Oscillator, is certainly the most important part of any console. This particular console utilizes 7 individual voltage controlled quadrature oscillators. I've always wanted to play around with the BB4423 but was never able to get my hands on one.

Click to expand...

thanks for your attention,
i know this is an old subject,but i want to acheive to this for myself
and i need info about the exact frequency of two galvos that i use for scanning.
the square i saw in that video you sent isnt my goal,i want to creat a filed square plate.

great stuff mate! love it, this is what i am hoping for, i am a real big synthesizer geek, and feel that this is good material to combine with laser

i am a real big synthesizer geek, and feel that this is good material to combine with laser

Click to expand...

Absolutely! One of the last features I added to the console was audio in and out. The audio out can be used to attached to an amp to be able to see and hear what the console is producing. Here's a video I put together a while ago: https://www.youtube.com/watch?v=RxnU4dj_ilE

enjoy!