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Thread: OK- Another ground Question?? Sorry! :(

  1. #1
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    Default OK- Another ground Question?? Sorry! :(

    LOL-

    ground this, ground that. - this, -that. input minus....ouput differential...tied together, floating ground...common ground....

    I HATE GROUNDS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! LOL...

    OK, seriously-

    Maybe im making more out of this that i need to be.

    hooking up scanpro 30ks-

    I got the power supply output of +24V being wired to the Inputs on each AMP for the galvos +24V input. (simple enough)

    I got the power supply output of -24V being wired to the Inputs on each AMP for the galvos -24V input. (simple enough)

    NOW-

    next to the V1 (24V) and the V3 (-24V) are 2 connections for "G."

    im *NOT* using those connections for "GND" on input on the amps correct???

    this is being connected to an FB3 DAC by the way...

    SUMMARY-

    +24V OUT ON POWER SUPPLY wired to +24V on amp input +24V
    -24V OUT ON POWER SUPPLY wired 20 -24V on amp input -24V

    Signal in - (pin 1) on amp driver connected to X- from input from ILDA DB25 pin 14
    Signal in + (pin 2) on amp driver connected to X+ from input from ILDA DB25 pin 1

    Signal ground (pin 3) on amp driver connected to "G" connection on Galvo power supply. our should that be connected to ILDA DB25?? (or not connected at all???

    -Marc
    Attached Thumbnails Attached Thumbnails SCANPS 001 copy_1.jpg  


  2. #2
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    Default

    Connect the g connection of the psu to the ground of the scan amps - the 2 pins in between -24 and +24 pins on the amps

    also connect ilda ground to the g connection on the supply

    KVANT Australian projector sales
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  3. #3
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    Default

    Yes, you will need to connect that G to your scanner amp. And in fact, depending on the supply, you may need to connect both G together, right at the power supply itself.

    Lastly, as Dave wrote, you will want to connect the ILDA DB25 pin 25 to the G -- AT THE POWER SUPPLY.

    And most importantly, don't connect the ILDA DB25 pin 25 to anything else!!

    Best regards,

    William Benner

  4. #4
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    Exclamation

    Quote Originally Posted by Pangolin View Post
    Lastly, as Dave wrote, you will want to connect the ILDA DB25 pin 25 to the G -- AT THE POWER SUPPLY.

    And most importantly, don't connect the ILDA DB25 pin 25 to anything else!!


    Now I am confused, more than ususal... Before I explain, or instead of, can someone... Bill maybe, , draw a small picture or diagram, of where all the wires from an ILDA plug should be connected. I am sure most are stupidly obvious, but this pin 25... I have pin 25 hooked (daisy chained) to all kinds of places, laser negatives, galvo ground... except, the "Ground" on my galvo power supply... I think. I... yea, just a diagram would clear a lot of things.
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  5. #5
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    There is another huge thread about this somewhere on here and there were many opinions about whether or not it really made much difference. But, what was suggested was to connect pin 25 to the power supply ground. I think it was also suggested to leave the ground pin at the signal input of the scanner amps either disconnected or connected directly to the power supply ground. Some were connecting it to pin 25 which would possibly create a ground loop (whether or not it really caused any issues was debated). Most likely the signal input ground pin is connected to the ground of the scanner amp on the scanner amp PC board so connecting it to the power supply it isn't necessary. But I can't say that for certain without actually checking or looking at a schematic. Anyway, I hope I remembered everything correctly.

  6. #6
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    ok...on the input of my scanner amps,

    there is a "signal Ground." What the F*#k does THAT connected to????

    I got the 2 "G" connections on my PSU connected to the "GND" inputs on the amps. am i using this "SIGNAL GROUND" for a connection...???

    I think where myself and A LOT of other people are getting confused is every manufacturer labels their "GROUND" differently. or the "signal" on the "GROUND" line is different.

    ground, shield, negative, signal ground, ILDA ground, 1 ground connection, 2 ground connections, star ground scheme, ground loop, ground reference...???

    maybe ONE ground reference would be nice!!! a single term which definitively means ONLY ONE THING!!!!!!!!!!!!!

    what is my "SIGNAL GROUND" hooked to????

    -Marc

  7. #7
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    and you forgot .... " GROUND control to major Tom "

    connecting all the grounds to pin 25 wont show too much of a noise ( ground loop ) issue when you have all your cables localised, Meaning your PC, Dac, Projector are all plugged into the Same supply, ( derived from the same wall outlet )

    BUT... will cause a major issue and become very apparrant if you are connecting via a long cable accross a venue where for example the stage may be run from a seperate phase and ground, than the desk at the back of a venue, because the grounds will be at a slightly different potential, this will cause mains hum to be induced into all the signal cables,

    the onlyway to solve this will be to lift ( discconect ) the gound at one end .... but this then becomes an electrical safety hazzard

    hope this helps .... Karl

  8. #8
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    Here's a simple test that should be completely safe and tell you something about the nature of your ground situation.

    Turn everything OFF!

    Get a continuity checker. You know one of those meters that goes beeeeeeeeeeeeeeeeeeeeeeee!

    Find Earth! Start with the center screw in the wall outlet. Check to see if you have continuity from there to a copper water pipe. Once you have established that you have a good electrical foundation of Earth, then check it against the metal chassis of your laser projector. Move from there to the chassis grounds on the power supplies. Check the input grounds on the scanner amps and the color modulation. Note that there should be ground potential in all sorts of places, but they are connected together by specific paths, like through the power cords to the outlets and through cable grounds and shields from one component to another. Once you have gone over your whole system (OFF) you can start disconnecting and reconnecting individual cables and stuff to better understand and prove to yourself where all of your ground connection are from one piece to another. UNPLUG EVERYTHING from AC power and go over the continuity checking again. Check to the end of the AC cord third prong. This time, take a look and see if the power switch on any devices changes the ground connation from one part to another. By the time you go over all of this, you will know a lot more about your grounding situation.

    James.

  9. #9
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    James, back before you joined up (I think) on the board there was a big heated discussion about grounding. We all agree with what you just said about being able to check with an ohmmeter but it goes further than that. You won't be able to detect ground loops with an ohmmeter and that's basically what the issue was all about.

  10. #10
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    Is it not true that ground loop hum comes from multiple paths to ground? All I am suggesting is that you should become familiar with all of the paths that exist. Once you create a good mental diagram, you might notice that there are other ways to do it that might be better. Every hand-made system is going to have it's own characteristics.

    James.

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