Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: TTL modulation: High enable or disable?

  1. #1
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
    Posts
    2,333

    Default TTL modulation: High enable or disable?

    Hi group, I'm building a simple laser driver that can be modulated at high frequency. Currently the laser is driven at full power when the input is low and when the input is high the laser is shut off. Other drivers such as the Die4 use opposite control. Will this be an issue with common show hardware/software, or is there typically a setting or jumper for inverted blanking/analog drive?
    thanks.

  2. #2
    Join Date
    Feb 2005
    Location
    Florida
    Posts
    802

    Default

    Hi, What you want is the High enable
    That seems to be what most laser companies use.
    However, In the electronics field, Im used to the opposite (high to disable).
    So, I can understand the confusion.
    I dont think too many drivers allow for a selection for inversion..
    Ive not seen one here anyway..but, You may have to build an inverter user part of a hex inv chip like the 74hc04 or similar.
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  3. #3
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
    Posts
    2,333

    Default

    Thanks for the resp. As I want it to be analog or digital modulation I'll have to use something other than an inverter, oh the fun. It'll be an opportunity to improve the linearity, though.

    What Voltage range do most alanog drivers output, and is it bipolar?

  4. #4
    Join Date
    Feb 2005
    Location
    Florida
    Posts
    802

    Default

    Opps sorry, didnt see the analog reference. You had TTL in the title.
    You will need an op-amp to invert the analog signal. Altho I have seen some Chinese drivers use bipolar transistors, I dont know if I like that.
    Output depends several things, The op-amp, the regulator and the voltage drop of the output device.
    Most on the market use bipolar output, Robin and I prefer FET.
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  5. #5
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
    Posts
    2,333

    Default

    Allright, the specs are looking to be DC-200KHz 0-5V analog modulation, DC to 10MHz 0-5V digital TTL bandwidth. I intend to use it for a digital audio transmission project, but other uses I'm sure will pop up.

  6. #6
    Join Date
    Sep 2007
    Location
    Wiltshire
    Posts
    85

    Default

    Why not use one of Robins drivers? A mere fiver (UKP) for the pcb and handles analogue and TTL modulation.

    PS you want TTL hign to switch on.


    http://www.die4laser.com/dvd-rec/Die4Drive.htm
    A lovely childhood. Just me my mother and the voices.

  7. #7
    Join Date
    Oct 2006
    Location
    Central Florida
    Posts
    7,067

    Question

    Quote Originally Posted by drlava View Post
    Allright, the specs are looking to be DC-200KHz 0-5V analog modulation, DC to 10MHz 0-5V digital TTL bandwidth. I intend to use it for a digital audio transmission project, but other uses I'm sure will pop up.
    Will the Die4Driver do those specs?
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  8. #8
    Join Date
    Sep 2007
    Location
    Wiltshire
    Posts
    85

    Default

    The first 2 I know it will. Not sure about the third. I'll hook a scope up later and see.
    A lovely childhood. Just me my mother and the voices.

  9. #9
    Join Date
    Sep 2007
    Location
    Wiltshire
    Posts
    85

    Default

    Right, just hooked my driver up to scope and it seems to drop off around 1 Meg.
    A lovely childhood. Just me my mother and the voices.

  10. #10
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
    Posts
    2,333

    Default

    I specifically wanted this to work at S/Pdif digital audio frequencies. Most of the drivers out there use op-amps for feedback, which, while accurate and simple, have trouble in the MHz range, especially with fast edges which are necessary for S/Pdif timing. This driver uses discrete transistors for the modulation.
    Last edited by drlava; 10-19-2007 at 06:09.

Posting Permissions

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