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Thread: TTL signal generator

  1. #1
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    Default TTL signal generator

    Hi guys,

    Having read the topic about "jellybeaning" I got to think, how can a simulate a TTL signal?. I have a laser module that I haven't been able to fully test, so I would like to see how it performs with TTL.

    As some of you may know, I'm in the process of building my first laser projector, but I don't have everything ready yet, so I can't use the DAC or software to run the signal to my laser. I was thinking of some sort of homebuilt project for this. Perhaps something with variable frequency?

    I don't know, can this be done? or should I wait until I have everything up and running?

    thanks in advance

    Jonathan
    Remember the future?, That'd today, as you imagined it yesterday.

  2. #2
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    Default

    Its quite simple to build a small circuit to generate a ttl level pusling signal. Probably the easiest way would be with a 555 timer circuit. I'm sure if you look around on the web you can find simple schematics for one. One 555 timer and somewhere around 3-4 support components (resistors, timing cap and pot). The duty cycle will vary quite wildly. If you want a nice 50% duty cycle to test a diode, then you can run output signal from the 555 timer circuit into the clock input on a J-K flip flop chip. This will give you a perfect 50% duty cycle at exactly 1/2 the frequency that the 555 is outputing. If I get a few minutes, maybe I can draw up a simple schematic if you are not able to find one online.

    Good luck,
    David Zurcher

  3. #3
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    Default

    Thanks for the info, I'll start looking around.

    If you could draw a simple diagram I'll appreciate it too
    Remember the future?, That'd today, as you imagined it yesterday.

  4. #4
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    I found a very simple diagram for this, I think. It's a square wave generator, using a 74HC14, one resistor and one capacitor.

    Check it out. http://www.interq.or.jp/japan/se-inoue/e_ckt13.htm

    Do you think this could work?
    Remember the future?, That'd today, as you imagined it yesterday.

  5. #5
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    It's not very frequency stable but it sure would be an easy way to do it.
    You know, I have one simple request. And that is to have sharks with frickin' laser beams attached to their heads!

  6. #6
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    Thanks groover, I'll try it then. I just want to test my laser and see how it performs with TTL, guess this is enough :roll: .

    On the other hand, if I wanted to test it's abilities with analog blanking, would a triangle wave work? is there any easy way of doing it? :?:
    Remember the future?, That'd today, as you imagined it yesterday.

  7. #7
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    If you want to do a Little Soldering, Her eis a Chip that could work for you!, And YES Triangle wave would work fine, Sine is fine too..
    http://www.intersil.com/data/fn/fn2864.pdf
    CREATIVITY AT THE SPEED OF LIGHT!
    www.laser-ad.com

  8. #8
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    Jonathan,

    I'll have to do some digging, I'm sure I have an old drawing around somewhere. I have not built one in probably 3 years. Your best bet, if you are also looking for something to produce analog signals as well as ttl, is to simply purchase a function generator from ebay. You can probably find one for less than $100 usd. I would try and look for one with an led readout of the output frequency though so you know what you are working with. Would make it very easy to determine the limits of your laser. You can also buy two of them and use them to make a very nice abstract generator! 8)


    David

  9. #9
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    Or if you want cheap try this one...
    http://cgi.ebay.com/HARRIS-SEMICONDU...QQcmdZViewItem

    Its also based on a 8038 chip..
    However unless you have a counter or scope It would be tuff to know what frequency its putting out but its a start..
    or ..
    Find a generator with a freq knob or dial .. Most will put out TTL with variable output.
    You can find old Waveteks on ebay (model 145, 182, 184 etc) as they have DC output as well. Great for testing analog modulation !!!

    also B&K's can be had cheap too !
    "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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    thanks guys for your help, I'll see what I can do. I don't think I'll be buying anything yet, as this is more like a home project and I don't really have a use for something more advanced.

    I'll go first with the 74HC14 version as I already have that chip at hand and, depending on the results, I'll try the 8038 chip also, although that promises to be a bit more complicated. I may also use the 555 timer chip .

    Let's see how this all turns out :P
    Remember the future?, That'd today, as you imagined it yesterday.

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