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Thread: Modding from TTL to Analogue

  1. #1
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    Default Modding from TTL to Analogue

    Is there any way of changing a laser from ttl to analogue.
    The first one that I want to do is the same as this
    that dave (Lasershow Parts) sells. He does offer it in ttl or analogue so I expect there is only a slight difference.
    Maybe you can advise me dave?

    Jim

  2. #2
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    Hi Jimbo..

    No, not easily done... but coud be if you are able to redesign the input
    section and the reference.

    It would take some rebuilding of the driver board for sure..

    I've done a few , Its not easy.
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

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    I am also curious about this. I have this green dpss that is WAY too powerful for my red and blue. I was messin around with the PSU the other day and it popped apart. No damage but it made me wonder, isn't the main difference between analoge and ttl in the power supply? If so, is is something that can be changed or replaced? :?
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

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    It is in the power supply, but the differences are not trivial.

    You *can* modify a TTL power supply to give you analog blanking, but there is a good bit of work involved. The problem is that you need to protect the laser diode from a sudden in-rush of current. Even something as small as a .1 mf capacitor discharging can blow a diode if there's nothing there to limit the current.

    There are a few people that will convert PSU's from TTL to analog for you. Not sure how expensive it is to have done, but I think Fred (Astroguy) had it done to one of his green DPSS units. Might want to ask him...

    Might also want to contact the manufacturer and see if they sell a separate PSU that supports analog blanking.

    Adam

  5. #5
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    When you order some of the lasers they list them as ttl or analogue which you presumably ask for whichever you want.
    When I got my blue from extreme lasers I didn't specify which I wanted and a ttl one came. The analogue would have been the same price.
    On all the photo's that I have seen the PSU looks the same so I am presuming it is just a manufacturing option.
    Looking at the psu for my ttl unit there is a section of the board that is unpopulated near the output.
    At present I am reverse engineering the board to check out the circuit and hopefully identify what the changes would be.
    I have asked dave to take a close up picture of the driver board in the psu of the blue analogue laser that he sell butr at present he hasn't got one in stock.
    If anybody else has the same analogue psu for their laser I would be grateful if they could send a pic.

    DPSSL PSU


    TTL driver board inside psu



    Jim

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    Well after many hours with my meter, eyeglass and datasheets I've finally drawn the complete driver board and schematic for it.

    The board layout is here.

    And the schematic is here


    Jim[/img]

  7. #7
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    Quote Originally Posted by marconi
    Hi Jimbo..

    No, not easily done... but coud be if you are able to redesign the input
    section and the reference.

    It would take some rebuilding of the driver board for sure..

    I've done a few , Its not easy.
    What about building an external analog to TTL converter box? It seems like it would be possible to convert an analog input to TTL with PWM, using quasi-CW up to the max frequency of the TTL input. ???

    Does anyone know if such an item exists, and if it would be effective?

  8. #8
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    Quote Originally Posted by eyceage

    What about building an external analog to TTL converter box? It seems like it would be possible to convert an analog input to TTL with PWM, using quasi-CW up to the max frequency of the TTL input. ???

    Does anyone know if such an item exists, and if it would be effective?
    Quit typing in Greek dammit... IT makes my head hurt... :?

  9. #9
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    What about building an external analog to TTL converter box? It seems like it would be possible to convert an analog input to TTL with PWM, using quasi-CW up to the max frequency of the TTL input. ???

    Does anyone know if such an item exists, and if it would be effective?
    Sorry, not possible

    Remember the TTL circuit is just an on or off circuit, nothing in between is possible.

    Hey JimBo , Damn Nice job on the reverse eng drawing, pretty-well matches what I have here
    in my older CNI blue unit.
    Have you changed out that 74ls08 out yet an got your unit working?

    Anyhow...To add analog ,. one would need to interupt the path from the TTL switched reference
    and change it to an op-amp control .. the area where the output of U7 (pin 6) is.

    See the 1.22 v zener here V1...this is the reference...it is getting its power +5 volts
    from the TTL chip. but this is where the fun begins.
    You would need an op-amp with an input range of 0 to 5v with an output of 0 to 1.22volts
    and possibly remove the zener and limiting resistors as anything above 1.22 would be clipped.
    not much range to say the least. but thats all it would need to tickle it.

    This way you wouldnt disturb power adjustment pot setting.

    altho, You still would only get almost 10khz analog this way because of what they chose of output driver op-amp and output transistor
    They need to be changed out ... FET output would help too

    Yeah , looking at the design makes my head hurt too!!!
    I am also trying to use that board drawing to figure out what they did for the blank spot..I could fill in the values
    emperically for a start.

    Keep up the good work.. it'l pay off
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  10. #10
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    At least you understand it and can speak about it... I just get a throbing sensation... ops: I hadn't even opend the attachments... JimBo, where's the blue man...

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