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Thread: differential board on fb3

  1. #1
    Join Date
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    Default differential board on fb3

    anyone had any experiance with the fb3 addon differential board
    after solving a few teething troubles i tried out the diff board
    wired up as ilda standard pin 1&2 +xy, pin 14&15 -xy
    and only get a quarter image displayed any ideas ?? or do they use different pins?

  2. #2
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    Default

    Hi Badger,

    That's a coincidence - I'm playing around with one of those boards today and having similar problems as well! I'm going to have to drop off it for the moment and carry on later in the week though.
    Your're not alone!

  3. #3
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    Default

    It could be that the both of you just don't have it connectd correctly, but I don't know just by this verbal description. What happens when you use the system without the differential board?

    Note that if you are using Chinese scanners, I really recommend that you do NOT! use the differential board, because the only thing that you will succeed in doing (when it is all hooked up correctly) is doubling the size of the image. Normally Chinese scanners really can not handle "double the size"... What's more, as I have said many times, the onus of differential signaling is on the receiver, not the transmitter...

    If you send me your system, I can figure it out. Otherwise, it is difficult to communicate about visual phenomenon using only words...

    Bill

  4. #4
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    Default diff board

    i have mine connected as per qm2000 pinouts on 25 dsub pins 14 and 15 for xy -
    my chinese scanners are just fine on differential with out it i just get small image i had them connected differential on the alphalite that i had
    should i just turn up size on the scanner amps they are the cheap chinese ones that look the same as dt40 pros just a red pcb
    will post a picture as soon as i can

    regards
    chris green
    Last edited by badger1666; 04-06-2008 at 23:05. Reason: forgot something

  5. #5
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    Default here pics

    here are a couple of pics excuse no blanking on red wire came off did not have solder iron handy if you cant help bill can you send me sca
    matic using non surface mount components and i will make another on strip board
    thanks
    chris
    Attached Thumbnails Attached Thumbnails DSC00096.JPG  

    DSC00095.JPG  


  6. #6
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    Default

    Hi guys,

    I received a phone call from Pete Hartfree tonight, who reported the same problem. The explanation is simple, and answer is also simple. Unfortunately, I can't give you the answer...

    Here's the situation. Hardly anyone uses those differential boards. Normally, when they are required, we have them sent from our Central Europe office, and they were designed and implemented by Ante, who is the director of that office. I personally had never seen one of these differential boards in my life, until Pete sent me a picture of one...

    I know what it does and how it works AND I know that it requires additional power supply wiring. There are wires that you need to connect to the +/-6V on the DMX Daughterboard. Pete didn't realize that, and neither did you guys. So that's your problem.

    Unfortunately, having never seen one of those boards myself, and having never made the connections myself, I can't tell you where to connect it. Ante can, but he is at a tradeshow, and won't return to the office for a few days. So we will get you an answer in a few days.

    In the mean time, in talking about this with Pete, I realize that there must be a mis-step in our shipping somehow. My guess is that a few people said "and differential board" while ordering, and either Hayden or Paulo merely stuffed the differential board into a bag and shipped it, without giving it a second thought that -- oh by the way -- the customer probably doesn't know how to connect this... When they ship from our Central Europe office, Ante actually makes the power supply connections before they ship, so it is no problem. So basically, we need to learn where the connections go in the main Orlando office, and then make sure we connect it before shipping. That will improve the customer experience in the future.

    HOWEVER, let me recount the two points I made in my reply to Pete:

    First, if the FB3 is the only source of signal you have, AND if you have Chinese scanners, then I wouldn't even recommend using that differential board. The only thing you will succeed in doing is doubling the signal, and Chinese scanners generate more heat and more nonlinearity with a wider scan angle.

    Second, it can make some sense to use that board if you have another signal source that you occasionally use. That way the signal level coming from the FB3 will be the same as the "other signal source". But that's about the only good argument for using that differential board.

    The FB3 was really designed to be, essentially, permanently installed into a projector, where you don't really need signal level compatibility with other sources, etc. It does very well at that job, and we have sold literally thousands of them (all NEO-NEON laser projectors have a FB3 inside, for example).

    Also, again, providing differential OUTPUT will not provide any benefit, even if you are driving 1000 feet of cable because, as I have said many times, the onus of differential signaling is on the receiver, not the transmitter.


    More to come once Ante returns...

    William Benner

  7. #7
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    Default diff board

    thanks bill
    i had connected mine to the 5v supply feeding the fb3 main board
    so thats not where it goes?
    so ante will let us know what to do when he is back?
    regards
    chris green

  8. #8
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    Default

    So it's neither how they are connected or a galvo problem then, as first thought

  9. #9
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    Hi guys,

    Please see the attached diagram. It should be pretty self-explanatory.

    Bill

    Click image for larger version. 

Name:	FB3DIF.pdf 
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  10. #10
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    Default thanks

    thanks bill works great, seem to get a lot more than double the size
    i know you said its not cool to use it on cheap scanners but without it
    i only get a max scan angle of 20 deg but with it its a bit to much
    shame the size pot thing gone from fb3 . would it be ok to have x&y pots on scanners inputs so i can adjust the size to whatever room i am in, or adjust scanners gain to have a better image size and do away with the diff board ?

    thanks
    regards
    chris green

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