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Thread: Grounds tied together?

  1. #1
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    Default Grounds tied together?

    I asked Adam this last night, and I just want to make sure I understood correctly...

    Off of the DB25 connector, I have the Color lines wired off of the standard ILDA pin out configurations.
    R+ pin 5
    R- pin 18

    G+ pin 6
    G- pin19

    B+ pin 7
    B- pin 20

    My question is....

    i know a lot of you wired all of your - color lines together. (R-, G-, and B-) tied together and then wired directly to ILDA pin 25 (GRND).

    Is it OK and the exact same result if i wired DIRECTLY to each color line. in other words-
    pin 5 wired directly to positive input on driver for red laser.
    pin 18 wired directly to - input on red laser.

    Pin 6 wired DIRECTLY to + input on green laser. Pin 19 wired DIRECTLY to - input on green laser.

    and so on with the blue laser.

    Pretty much just avoiding tying signals together and wiring directly.

    Is this ok?? Im assuming that the answer is yes. and this whole thing is prob just a dumb question. i just want to be sure.

    Does one way have a benefit over the other way?

    -Marc

  2. #2
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    Negative is NOT ground!

    In a balanced signal line there are three conductors, +signal, -signal and ground. I have never seen a color modulation device that actually takes a balanced signal input, but I understand they do exist. What you really want (I think) is just the positive signal and the ground. And, yes, the ground is the same for all of them.

    James.


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    Hi all

    I have my modulation on my lasers connected to

    R+ pin 5
    R- pin 18

    G+ pin 6
    G- pin19

    B+ pin 7
    B- pin 20

    no problems, my Gr and Blu are CNI and Red is Lasever, and as as the modulation is not referenced to Ground all it looks for is a 0 to 5v input which you will get accross the differental
    output fro the Dac ( +/- 2.5v ).... if your laser modulation input is ref to ground then you will need to connect pin 25 to 18, 19,20 you should still get the full swing 0 to 5v from pins 5,6,7,

    this works with mamba and with qm2000 Dacs but you will need to check your Dacs design before shorting to ground

    all the best .... Karl

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    Quote Originally Posted by Banthai View Post
    Hi all

    I have my modulation on my lasers connected to

    R+ pin 5
    R- pin 18

    G+ pin 6
    G- pin19

    B+ pin 7
    B- pin 20

    no problems, my Gr and Blu are CNI and Red is Lasever, and as as the modulation is not referenced to Ground all it looks for is a 0 to 5v input which you will get accross the differental
    output fro the Dac ( +/- 2.5v ).... if your laser modulation input is ref to ground then you will need to connect pin 25 to 18, 19,20 you should still get the full swing 0 to 5v from pins 5,6,7,

    this works with mamba and with qm2000 Dacs but you will need to check your Dacs design before shorting to ground

    all the best .... Karl
    Have you ever tried leaving 18, 19, 20 out of it and just using 5, 6, 7 & 25?

    James.

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    Default

    R+ pin 5
    R- pin 18

    G+ pin 6
    G- pin19

    B+ pin 7
    B- pin 20
    This is perfectly fine for the QM2K since, internally, the -r, -g and -b are all tied to ground. Use to be that they were truely differential outputs, but I think because of many folks mis-wiring the thing, and almost no laser supporting differential input, they just made the color modulation outputs single ended, with the -R, -G and -B actually being ground.

    X and Y are another story, these are truely differential outputs, if you have a single ended scanner amp, then you would want to tie -X and -Y to ground.

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    There is an excellent "hardware specific" answer! That should tell you something!

    James.

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    I found out the hard way because at first I used only pins 5, 6, 7 and a common ground. That worked with my Moncha DAC because it 18, 19, and 20 were tied to ground and 5,6,7 varied between 0 and 5. But then I hooked it up to an EasyLase DAC and my lasers didn't come on like they should. So, I went to using 5,6,7 and 18,19,20 and it worked and now I am happy with both DACs.

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    Quote Originally Posted by carmangary View Post
    So, I went to using 5,6,7 and 18,19,20 and it worked and now I am happy with both DACs.
    How are your cables made? Do you hook 18, 19, 20 to the shield? Are they all independent?

    I guess I could see a _pair_ of wires inside a shield with (5, 18), (6, 19), (7, 20) in the wires and 25 to the shield, left unconnected on the color mod input end. But what's the point? It's freaking single ended!

    James.

  9. #9
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    [QUOTE=gottaluvlasers;52609]I asked Adam this last night, and I just want to make sure I understood correctly...

    James, older QM2000 have a "gyrator" circuit on x and y, if you hook it to a differntial amp, its differntial, if you ground the minus side of the diff pair, it doubles the voltage on the plus side to feed -5<>0<>+5 to a single ended scanner amp. At least the first gen quadmod 2000 did that. color channels do not gyrate. At least thats how it was in St Louis last month and at LaserRave (tm) last year.

    Steve

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    Quote Originally Posted by James Lehman View Post
    How are your cables made? Do you hook 18, 19, 20 to the shield? Are they all independent?

    I guess I could see a _pair_ of wires inside a shield with (5, 18), (6, 19), (7, 20) in the wires and 25 to the shield, left unconnected on the color mod input end. But what's the point? It's freaking single ended!

    James.
    Can't remember if I have a shield or not. But the point is that 5,6,7 to 25 on the EasyLase is not 0-5v. The negative (or ground) wires to the laser modulation must be connected to 18, 19, 20 in order to get the full modulation potential. Maybe 18,19,20 are all tied together in the DAC but they obviously aren't at the same potential as 25.

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