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Thread: Precision galvo system on the cheap

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    Default Precision galvo system on the cheap

    I am interested in putting together a precision xy galvo system for vector measurement purposes. I am not too concerned with speed, just with precision feedback of position.

    Looking on ebay, I see a lot of equipment from GSI lumonics/Cambridge Technology. The sad part however, is that usually the galvos and the amplifiers/controllers are in separate listings. Also, when I find a listing where the two are paired together, I can never find a manual for the controller.
    Without a manual, the controller board is useless to me.

    Part of me thinks that if I can:
    - get generic galvo amplifiers for these motors
    - get the pin out and specs of these motors
    That I can implement my own PD controller to close the loop. Again though, the documentation of anything I look at on ebay just isn't there.

    How should I proceed?

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    Pangolin's new 506c galvos are precision with excellent linearity and are a very good value. Check out the datasheet. http://www.scannermax.com/pdf/Compact506.pdf. For the best precision, look at the stats for the PRO model.
    Last edited by absolom7691; 08-07-2014 at 19:18.
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    yes, except pangolin does not currently sell drivers for them.


    Quote Originally Posted by absolom7691 View Post
    Pangolin's new 506c galvos are precision with excellent linearity and are a very good value. Check out the datasheet. http://www.scannermax.com/pdf/Compact506.pdf. For the best precision, look at the stats for the PRO model.
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    You should talk to me and not reinvent the wheel.

    Please tell me about your application, desired scan angle, and speed. Size of mirror needed.

    There are many models of amplifier and galvo, and I have many of the manuals for GSI/Cambridge.

    Besides. Mrs Frisbee at Cambridge has all the books as well. Cambridge bought GSI, and for many models the data is available.

    Building galvo amps requires a type I PID loop for accuracy, and that is a triple nested loop.

    Depending on your mirror size needs, we can get you going on CX660 amps on Ebay or with Cambridge Galvos on generic amps.



    Steve
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    I've got some Cambridge 6230 scansets here (2 scanners, 1 X and 1 Y mirror, with 2 SN matched 678 drivers). They have silicon mirrors coated for 1064nm. I don't have the XY mount for them. Not too hard to machine something up or just get the OEM mount from Cambridge. Used, but tested and guaranteed to meet spec. I'd like $1K / set.

  6. #6
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    Ok, so I have done a bit of thinking.

    Absolum
    The price point of these scanners is very interesting. One thing I am curious about is how the errors could be compensated for in the control set up.
    Without compensation, I do not believe that the specs on the Pro model meet my requirements for error.

    mixedgas
    For my application I am tracking and locating a target in 3d space using an interferometer and sensors. Not only is precision required, but accuracy as well, as the mirror angles are to be used in the measurement calculations. Laser is 1mW, 633nm.

    For mirror size, I may require 1-1.25 inches diameter, as interferometry requires an offset return beam.

    Speed is not a huge concern as the target is a couple meters away and is limited in how fast it will move. I do not need to create an animation on my wall, I just need to track a target a couple meters away moving a few m/s. Any galvo should be suitable for speed/acceleration/step response.

    For angular travel anywhere from 20-40 degrees is fine. A wider angular travel without trade offs in accuracy is preferred.

    The major concern is accuracy. So linearity, scale temperature drift, and offset drift are all of concern. Hopefully I can find a system that compensates for linearity issues and scale drift.
    I wish to be accurate to 0.0001 degrees or better. Is this at all reasonable? Perhaps because I do not require high scan speed, I should consider options other than galvos.

    If you have documentation on any of the following equipment could I have it?:
    http://www.ebay.ca/itm/Cambridge-Tec...item2c68ec7f9d
    http://www.ebay.ca/itm/Cambridge-Tec...item2ec2883927
    http://www.ebay.ca/itm/LASER-SCANHEA...item27e333e573

    I would also appreciate any general application notes about scanners or unrelated spec sheets, just to get a feel for things

    Junktronix
    My budget is very low, hobbyist level. About $400 is all I have to spend, not including the daq. I believe I can obtain the equipment I need at this price, if I am willing to take a bit of risk. Maybe that is unrealistic. I will soon find out.

  7. #7
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    Your lucky day..... Or God is looking out for you......

    I have the two sets of DOCs for the 650 single axis amp board pictured. They have slew rate limiters, which aid in precision but cost you speed. You need two 650s per X-Y head, so you'd have to buy both auctions.

    I have a few of the 650s with 6350 series high accuracy capacitive positioning scanners and power supplies that were used in carbon fiber layup machines. They have big enough mirrors on them to collect the return light, which is an issue with the small scanners. In fact the machine used a 5 mW red laser diode launched through the collection optics, which the operator could use to measure position using a reflector. I can toss in one of those laser/detector assemblies.

    The other board in the machine was a dual 16 bit precision DAC driver and a precision window comparator circuit. The external PC that controlled it read the difference and error signals and decided when to enable the laser, and if the reflective target was present.
    It was good enough to read to .1 to 1 mm at several meters depending on the target. They did this by scanning past the known size retroreflective target (octagon of bike reflector tape) and interpolating.

    System is Made in Canada.... Go figure... I take it you'd love to have the scanners and boards if they met your specs.

    The Interface is a series of 8 bit digital latches on a 25 pin Dsub for receive and a 25 pin Dsub for position and transmit. A good Technician or EE student could figure out the addressable latch IO structure in about 30 minutes. It would be easily adaptable to a microcontroller or lab view. The work has been done for you. The 650s I have a 16 bit digital input using a parallel structure or you can add a jumper and use your own analog signal. 1990s technology, easy to interface, no SPI or Serial.

    According to the sparse system manual, they used a lookup table in the external PC to fine linearize the galvos.

    You'd get 2 main power supplies, one small power supply, 2 scanner amps, 2 scanners with large thick mirrors on reusable/removable mounts, 1 logic/latch board with position comparator. Includes the XY mount for the scanners. 1 launch optic with a PD board and a LD board. All the cabling.

    As for the housing:

    The weatherproof housing weights the better part of 40 pounds and I need it. It barely fits in the trunk of a car. Shipping on it would break the bank, anyways. The mount for the housing weights in at 80 pounds and is made of 5 inch steel pipe.

    I'll PM you. Send back a PM with a email address if you want to look at the scanner manuals and unit pictures. I'm leaving for a conference in the morning, so if you need a set shipped ASAP, let me know, otherwise it will be a week before I can get back to you.

    As for Ebay, The other set and amplifiers I can reverse engineer, but that takes time. Docs for it are not available, its custom.
    Its based on a cross between a Mini-Sax and a 67xxx family from what I can see.

    I will test the galvos before shipping.

    I can sell and ship with the funds you have available.
    I purchased the system for a trial for a proposed outdoor scanning system to measure fog in Nova Scotia. I'm just recovering my cost.

    Steve
    Last edited by mixedgas; 08-13-2014 at 07:22.
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  8. #8
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    Quote Originally Posted by mixedgas View Post
    Your lucky day..... Or God is looking out for you......

    I'll PM you. Send back a PM with a email address if you want to look at the scanner manuals and unit pictures. I'm leaving for a conference sthe morning, so if you need a set shipped ASAP, let me know, otherwise it will be a week before I can get back to you.

    Steve
    Yes,please send. Have you sold everything already?

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