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Thread: How do I do the blanking (maybe a question to SBK)

  1. #1
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    Default How do I do the blanking (maybe a question to SBK)

    I got the DAC from www.mylaserpage.de
    And i got a laser head from spec.

    The DAC blanking output is 5volt + OUT !!

    And the laser got 3 wires out, when I short 2 of them togheter ble laser blank OFF !!

    So if I connect the blanking from my DAC into the laser, there is NOTHING !

    So what i did do was to use a relay from the output, 5volt + from dac.
    And then connected the wires from the laser into the relay output !

    Then the blanking was perfect

    But becouse of the relay slow speed, I think the blanking time is slowing everyting down !!

    So what I need is a chip that work like a relay (that will work with full speed)
    or mabye a advice how to do it !!


    SBK did use the same DAC as me, so i wonder how he did do it :roll: :roll: :roll:

  2. #2
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    Liteglow... Look at my post here

    http://photonlexicon.com/forums/viewtopic.php?t=231

    Sounds like you need to invert the blanking signal..
    Try looking for a HEX inverter chip or just a single or
    dual inverter chip..
    You will only need one of them inside the chip to do the job
    just ground the unused pins...
    Some come to mind..like 74hc04, 4069 , and the like

    Also, this circuit may work for you..it shows using two inverters but you can us just one for what you want to do..


    or , you could build a simple inverter using a transistor also in that post

    Almost any NPN transistor will work, is not critical
    Also the resistor values can be higher , use what you have that is close
    in value and work from there, it should work...
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  3. #3
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    Your laser blanking is not inverted, the input just have to be connected to the ground to blank...
    So, here I did the trick :
    I use a pull-down resistor. This resistor is between the Input of the laser and the GND of the Easylase. And the GND of the laser blanking is connected to the GND of the Easylase. So, when blanking (= 0V on the easylase blanking), the input of the laser blank is to the GND, so no laser.
    When the laser don't blank (=5V on easylase), the blanking input is at near 5V. Yes a current will go through the pull-down resistor, you have to calculate the highest resistor which still gives a good TTL signal to blank the laser... I don't remember the exact value, something like 2 - 5 kOhm.

  4. #4
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    Thanx alot SBK

    I will try that tomorrow !!

  5. #5
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    Quote Originally Posted by sbk
    Your laser blanking is not inverted, the input just have to be connected to the ground to blank...
    So, here I did the trick :
    I use a pull-down resistor. This resistor is between the Input of the laser and the GND of the Easylase. And the GND of the laser blanking is connected to the GND of the Easylase. So, when blanking (= 0V on the easylase blanking), the input of the laser blank is to the GND, so no laser.
    When the laser don't blank (=5V on easylase), the blanking input is at near 5V. Yes a current will go through the pull-down resistor, you have to calculate the highest resistor which still gives a good TTL signal to blank the laser... I don't remember the exact value, something like 2 - 5 kOhm.
    Hi again..

    I`m sitting here to figure out what you say!
    But there is something missing !!!
    I connect Input of laser to GND (yellow to GND on DAC)
    And GND of the DAC to the GND of the blanking..... :roll: :roll: :roll:

    I think i have missed something...

    You dont have a pic or something that can explain this a easy way


    My setup is like this:
    I got GND and Blanking on my DAC !

    And I have 3 wires from my laser: RED,YELLOW, BLACK !!


    So what do i do !!
    The only solution that works is when I use a relay from the GND+Blanking out from dac.

    And connect yellow+black into the relay !

    The problem is that a relay dont do blanking more than maybe 8000pps !

    this is a "#"#% problem... i just need a IC if there is any !?!

  6. #6
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    uhm.. i did try to connect blanking to GND and one to the output from the DAC (5volt)
    And the laser did go OFF ... but it did never go back ON !!

    So now the blanking is locked always ON !! :evil: :evil: :evil:


    That is great... err...

  7. #7
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    Hi Liteglow,

    Sure sounds like inverted drive to me..But I could be wrong!!

    That circuit I posted above (74HCT04n Hex Inverter)
    will drive any just about laser ,Inverted or not..with minor changes.
    .
    It depends on how many inverters in the IC package that you use.
    This is a Hex inverter, That means you can use up to 6 inverters in this chip.
    In the circuit above , pin1 is the blanking input,
    And pin2 is the blanking output...
    If it needs reversed ,pin1 is blanking input,. tie pin2 to pin3 and use 4 as the output.
    Since you already have 5volts somewhere, the regulator may not be needed.
    With each section of the chip it inverts the signal and as a benefit
    has more drive than some DAC boards can put out.
    You can also use this chip to drive solidstate relays to control shutters too!!!
    There are many different style of Inverter Chips out there..
    I just picked the most easiest to get..
    I hope this helps..
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  8. #8
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    Easylase USB? That unit should have an ILDA standard connector...

    If you use an optoisolator, it'll wire in just like the relay...

    In the schematic below, just replace that 5V line with whatever voltage
    is specified for the blanking on the unit...



    Also note that the ILDA ground does not attach to the ground of the laser/opto.
    If the laser is inverted and you have no way of specifying the inversion in
    the software, then a 7404 between the resistor and the ILDA connector
    would be perfect as Marconi suggests... Remember to ground all unused
    inputs on a 7404 to reduce "flapping".

  9. #9
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    Thanx for the reply...

    I dont have the USB, I have the LPT dac.
    And the output on it is 5volt blanking !

    The problem is that there is no 5volt input on the laser.
    The blanking is like a swithc you have on your light in the room !
    You swithch it OFF and you switch it ON !


    The only problem now is that the laser is DEAD...
    Maybe 5volt in where it was supposed to only have GND.....

  10. #10
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    Dark emitting diode? not good... That's possible if you tied it in reverse polarity.
    (5V where it expects ground and ground where it expects 5V)

    I assume you tried running it by itself to make sure... Which laser unit was it?
    If it's one of the New Laser Century units, then it turns on and off like I
    described above! If it's marconi's then it also runs like above, but the 5V
    may need to be a bit higher depending on which version you have.

    I don't know of any units which is turned on/off like a switch, but again I'm
    not sure which laser module you got.

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