Page 4 of 7 FirstFirst 1234567 LastLast
Results 31 to 40 of 68

Thread: Scan Pro 40

  1. #31
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default

    Quote Originally Posted by dave View Post
    Best suggestion would be to view the output of the correction amp with an oscilloscope... Then go from there..
    Quote Originally Posted by ElektroFreak View Post
    Then you can see the images on the scope screen just as they will be coming out of the projector. Simply viewing the signal is sufficient, but X,Y mode can help make setting the offset and gain easier.
    The scope is Dual Channel so I would be able to view both outputs at the same time.
    So the output from the galvos should look similar to what I see on the o-scope?
    Then would I just adjust the offset and gain on the correction amp to make it look like the ILDA test frame should?
    If that doesn't help would the tuning on the galvo amps need to be adjusted?

  2. #32
    Join Date
    Jan 2009
    Posts
    1,622

    Default

    If you are viewing the output in X,Y mode, the image on the screen of the scope should be exactly what the galvos are producing. If you have the DAC built and set up right, when you load the ILDA test frame in Spaghetti settings, you should see the ILDA test frame on the screen of the scope. Since the scope isn't taking blanking into account, the images will contain blanking lines.

  3. #33
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default

    Is the purpose of doing this so I can tweak around on the pots without blowing up the galvos on accident?

  4. #34
    Join Date
    Jan 2009
    Posts
    1,622

    Default

    While it does have that added benefit, the real purpose would be to determine if the problem is your DAC or your galvos. Also, as was previously stated, viewing the output as X,Y data on the scope just helps make sure that the gain and offset are such that the image is centered and not being clipped.

    There is clearly an issue somewhere along the line, otherwise you would be seeing the ILDA test pattern when you load it instead of a jumbled up mess. Viewing the DAC output on the scope just helps verify whether the DAC is at fault or not. If the DAC is working correctly, obviously the issue is with the galvos.

  5. #35
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default

    Duh, I should have figured that out as well. I will get it all hooked up to the Oscilloscope tomorrow, I have to go to school today :-(. Thanks.

  6. #36
    Join Date
    Jan 2009
    Posts
    1,622

    Default

    I was looking at the output you showed earlier and I was wondering why it looked familiar. I think I've had the same problem myself, and it was due to an errant blob of solder shorting to ground on the correction amp. If you haven't already, find some bright light and a magnifying glass and go over each joint and component on the correction amp. Look for bridges, blobs of solder, pieces of cut leads, anything that looks like it's out of place.. I'm fairly sure it's a ground issue. If it's not that, it could be a problem with your ILDA cable if you're even using one a this stage of construction.

  7. #37
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default

    I examined the correction amp but I couldn't find anything out of place. Dr. Lava actually assembled my kit so everything looked good on the board.
    I will hook it up to the Oscilloscope today and see what I find. It's possible I had the connections to the scanner amps made in correctly.

  8. #38
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default Its the DAC

    Well after hooking the dac to the oscilloscope I know its the DAC and not the scanners. The scanners are displaying the exact same thing as I see on the Oscilloscope.

    Now I have to figure out why the DAC is outputting this pattern, is looks like a jumble of points is just way outside the "square". If you look back a few posts, the image I projected from the scanners is the same as pictured below (except flipped in x and y)

    I also downloaded the ILDA test frame "b" to see what it looked like. It is about the same but with less points.

    When I scale the image down, the square is the only thing that shrinks. The distance between the square and the outside points stays the same. So the scale doesn't seem to affect the rouge points.

    Any Suggestions?
    Attached Thumbnails Attached Thumbnails photo 4.jpg  

    photo 3.jpg  

    photo.jpg  


  9. #39
    Join Date
    Jan 2009
    Posts
    1,622

    Default

    Quote Originally Posted by MisterWilling View Post
    Well after hooking the dac to the oscilloscope I know its the DAC and not the scanners. The scanners are displaying the exact same thing as I see on the Oscilloscope.

    Now I have to figure out why the DAC is outputting this pattern, is looks like a jumble of points is just way outside the "square". If you look back a few posts, the image I projected from the scanners is the same as pictured below (except flipped in x and y)

    I also downloaded the ILDA test frame "b" to see what it looked like. It is about the same but with less points.

    When I scale the image down, the square is the only thing that shrinks. The distance between the square and the outside points stays the same. So the scale doesn't seem to affect the rouge points.

    This is why I think it's a grounding issue. When you change the scale of the image, the only thing that should change is the X,Y galvos signal amplitude. The blanking channels will stay the same. Since you can see large parts of the test frame in the first image, parts of the image are getting to the galvos without being molested by blanking signals which is how it should be since the laser only blanks between lines. Therefore the blanking signals will skew parts of the image away from where they should be by about 5V, leaving other parts unchanged (the parts that are recognizable) when there is no activity on the blanking channels. Since both X and Y are affected because they share the same ground as the blanking channels, the image will be skewed diagonally rather than horizonally or vertically.

    Any Suggestions?
    There's a short somewhere on your board. I think one or more of the blanking signals are somehow getting fed to your galvos.. The square is encouraging, though, and you can see most of the elements of the test pattern buried in there.. I'm 99% sure it's a grounding issue. All the channels share the same ground, so if anything is shorted to ground it affects everything. Can you post some close-up shots of your sound card and correction amp in good lighting?
    Last edited by ElektroFreak; 01-26-2010 at 20:40.

  10. #40
    Join Date
    Jul 2009
    Location
    Dallas, Tx
    Posts
    372

    Default

    I don't have my camera to be able to get you a good close up but I will have it in a day or two.

    Since you're leaning towards it being a grounding issue, wouldn't I be able to only run the sound card in two channel mode and just run the galvos? If I can do that then I would know for sure.

    I just though about it, I have the laser output icon turned to "off" in spaghetti, would the blanking signal still be sent out when inside the projector configuration menu?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •