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Thread: 741 Op-amp wiring help please?! :)

  1. #1
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    Default 741 Op-amp wiring help please?! :)

    Ok, I'm desperately trying to invert the direction one of my scanners in order to do a mirror image show with 2 projectors. I'm using an FB3 with single ended outputs.

    On another thread someone suggested using a 741 opamp to invert the signal.

    Ok, so i have the 741's and I have a RS232 jumper box which I'm intending to use to house the opamp and wiring so i can add it into DB25 signal path as needed - HOWEVER, I'm a complete luddite about most electronics and haven't a clue which wires need to go to which legs, and which output legs need to go to the projector.

    So I have the following pins:
    X sig = 1
    X gnd = 14
    common gnd = 25

    Where do i have to route these to on the inputs of the opamp?

    Forever in your debt if you can help! I'm running out of time before the weekend!

  2. #2
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    Hi Norty

    basically you just need to use it as an inverting amp as in the pic below
    not knowing what the signal impedence you have, im guessing the resistor values at 10k ohm each is a good place to start




    hope this helps ... Karl

  3. #3
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    just a bit of quick scrawl ... so sorry for the lack of detail

    but this is a typical single to differental converter .... using the 2 amps keeps the output impedence the same and is reccomended

    karl
    Attached Thumbnails Attached Thumbnails diff amp 1.jpg  


  4. #4
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    Ok, so are you saying i need to add a 10kR resistor in series with the input, and another between the input and output legs? I'm not much cop with those diagrams... To be honest I'm not too sure which leg is which even.....


    edit: Oh god that diagram has just completely confused me further. My scanners are single ended too (there is a single 3 pin plug from my scanner board labelled X-G-Y), so I could do with a non-differential output, I'm really just trying to get the pin one pulling when it was previously pushing if that makes sense?

  5. #5
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    do a search on google for LM324 (try images)

    its a quad opamp package it would be ideal for both x and y axis

    or check here ... it will show you

    http://www.uoguelph.ca/~antoon/gadgets/lm324.htm

    but you will need to power it on a dual +/- and ground supply

    karl

  6. #6
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    Ok, without wishing to overcomplicate this, my other projector is already reversed in the Y axis, its just upside down, so i only need to reverse the X axis via this method (if I'm using it on its own I can do it in the software) I bought some 741's

    BTW, thanks very much for this...

  7. #7
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    before you go nuts doing all of this...

    what scanners and amps are you using? some amp boards have jumpers on them to set the inversion of the scanner. you can simply move a jumper to change up to down (or vice versa) and left to right (or vice versa). have you tried this??

    -Marc
    http://www.laserist.org/images/ildalogos/ILDA-logo_colored-beams_Corporate_150w.jpg

    ILDA- U.S. Laser Regulatory Committee

    Authorized Dealer for:

    • Pangolin Laser Software and Hardware
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  8. #8
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    Nope, explored that avenue a while back, they are the scaneco 10(12) or something very similar. Very few options on them.

    Once i get home I'll post up some pics of the opamp and label the pins. Perhaps someone can simply comment on which pins need to be connected to what, and if i have to add resistors between/in series with any of the connections?

  9. #9
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    Before you build a separate circuit -

    Have you considered just using a DPDT toggle switch to swap the X-axis inputs between your controller card and scanners? Bill Benner refers to this in his projector wiring article:

    http://www.laserist.org/laserist2008...onnections.htm

    You might want to try that first - if it works, it would be REALLY easy to include that in your projector, without having to build additional circuits OR changing settings in your software!
    Last edited by Stuka; 10-08-2008 at 09:16.
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  10. #10
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    Thanks, thats a really useful articel however I'm not sure that solution is going to work.

    I've already tried using a RS232 jumper box between the ilda cable and the ilda connector on the projector but it doesn't give any results at all unless its wired in the regular way (X sig to 1, X gnd to 14)

    I suspect that if i had differential ouputs then switching the -ve to pin 1 would do the trick but I don't.


    However, I did email Jimbo who sent me this rather wonderful diagram which explains it all!! So for the benefit of others who may come after me I'll upload the diagram for posterity! I should probably also link to this thread from my other related ones.....
    Attached Thumbnails Attached Thumbnails 741 inverter.jpg  


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