Page 1 of 2 12 LastLast
Results 1 to 10 of 20

Thread: TTL "Merging"?

  1. #1
    Join Date
    Nov 2007
    Location
    Cairns, Australia
    Posts
    1,896

    Default TTL "Merging"?

    Hey guys, I got my scanpro's today, wired em all up and everything works fine. The only problem, is ATM I only have a green laser. I know you can set the colours through DMX, but I want, for now, to just use sound/auto mode. What the problem is, since the board is designed for RGB, the places where the other colours are supposed to be are just "Blank". I was wondering if you could just connect all the TTL wires together, which would allow you to still have TTL, but using only green?

    Thanks

  2. #2
    Join Date
    Jun 2007
    Posts
    44

    Default

    Hello Things,

    It is unsafe to connect TTL outputs like the R,G,B outputs together directly, but you can do it safely by using three diodes like this:

    R output TTL ---|>|---\
    G output TTL ---|>|---+--- R|G|B output TTL
    B output TTL ---|>|---/

    You can use any small signal diodes like 1N4148 or 1N914. These will drop about 0.6V from the signal (so instead of 5.0V 'ON' signal, your laser will see 4.4V 'ON' signal), but it should not matter because the TTL input will consider anything above approx. 2.0V to be 'ON' signal.

    Kind regards,

    sonaluma



  3. #3
    Join Date
    Nov 2007
    Location
    Cairns, Australia
    Posts
    1,896

    Default

    OK Mate, thanks for the reply! I will have a red laser for it soon, but a blue is quite far off. So basically I just need to block the TTL signals going back to the driver?

  4. #4
    Join Date
    Nov 2005
    Location
    Melbourne, Australia
    Posts
    3,695

    Default

    actually, the best option would be, to use an or gate
    KVANT Australian projector sales
    https://www.facebook.com/kvantaus/

    Lasershowparts- Laser Parts at great prices
    https://www.facebook.com/lasershowparts/

  5. #5
    Join Date
    Jun 2007
    Posts
    44

    Default

    Hi Things, yes you need to prevent any output driving another output, because if they have conflicting signals they will waste a lot of power and possibly burn up trying to drive each other to different levels . The diodes prevent any of the outputs from driving any of the other outputs .

    Hi dave, yes you could certainly use a gate chip instead, but this would require something to mount the chip on, more wiring and a power supply . Since there won't be any difference in performance for this application, I recommend the diode solution because it's much simpler .

    Best regards,

    sonaluma

  6. #6
    Join Date
    Nov 2007
    Location
    Cairns, Australia
    Posts
    1,896

    Default

    Do you need a diode on BOTH of the ttl leads? I just put one on each positive, and direct connected the negatives, but it didnt seem to work

  7. #7
    Join Date
    Jan 2006
    Location
    Akron, Ohio USA
    Posts
    1,754

    Default

    If you had a LaserBoy DAC, you'd have a single, summed TTL channel.

    James.

  8. #8
    Join Date
    Nov 2007
    Location
    Cairns, Australia
    Posts
    1,896

    Default

    I'm having a problem finding a cheap 3-4 chan USB sound card around here

  9. #9
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,489,073

    Cool

    I'm having a problem finding a cheap 3-4 chan USB sound card
    I just bought a 6 channel USB sound card from the UK E-bay site. Cost me 10 Brittish pounds with free shipping. They have *tons* of them listed, and they are all buy-it-now for 10 GBP. (Around $20 US). They ship for free to Australia too.

    Have a look at this auction. If it's closed before you get a chance to bid, just look at the seller's other auctions and you'll find more.

    Adam

  10. #10
    Join Date
    Jun 2007
    Posts
    44

    Default

    Quote Originally Posted by Things View Post
    Do you need a diode on BOTH of the ttl leads? I just put one on each positive, and direct connected the negatives, but it didnt seem to work
    Hi Things,

    No, you only need three diodes to combine R, G, B into one signal. The TTL ground wire (negative) connects directly to the signal ground (e.g. ILDA pin 25). If you install the diode network on the DAC outputs as I have drawn above, then the TTL signal wire (positive) connects to the common terminal of the diode network.

    Are you sure that you're using the diodes in the correct direction? If the diodes use an arrow, it should be pointing from the DAC outputs to the TTL input. If they use a black/white band, it should be closest to the TTL input side.

    Best regards,

    sonaluma

Posting Permissions

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