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USB to serial question

Discussion in 'General Electronics Discussion' started by peter st, Jan 11, 2014.

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  1. peter st

    peter st

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    Jan 11, 2014
  2. peter st

    peter st

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    Jan 11, 2014
    it is to send readings from a chronograph to a computer via usb so the power source is the 5v from usb the chrono itself uses 3 of the batteries you would use in a laser pointer
     
  3. gorgon

    gorgon

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    Jun 6, 2011
    The USB to Serial TTL should not need an extra inverter to work at TTL Level. To answer what to do with pin 3, you need to read the manual for the device you need to communicate with. As far as I understand you can not connect this USB Device to a standard RS232 port.
     
    Last edited by a moderator: Oct 22, 2019
  4. peter st

    peter st

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    Jan 11, 2014
    i linked to it in my post sorry im new to all this
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Peter st, what you have done is called "hijacking a thread". In this case I have moved all the posts to a new thread and removed 7 of them which were confused by the change in topic of the thread.

    It would be wise to start a new thread for new topics in the future. I'll accept that it was an error, but now you've seen what happens, I'm sure you'll be more careful in the future.
     
  6. peter st

    peter st

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    Jan 11, 2014
    ok i shall try and explain as best as i can please note i do not have a clue so sorry if i seem daft
    i own a combro chronograph i found this wiring diagram for it
    http://www.combro.co.uk/cb625/m625-3.gif
    now what i would like to do is connect the chronograph to my computer with this cable
    http://www.amazon.co.uk/gp/product/B00F2F5HVK/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
    i belive it is a j9 connector i put onto the chronograph
    so my question is after i clip the j9 to the chronograph what do i need to do to make it work with the cable i linked to ie how do i build the circuit shown in the diagram to connet to my cable
    please correct me if im wrong on anything i will try to answer any questions with my limited knowledge
     
  7. gorgon

    gorgon

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    Jun 6, 2011
    The short answer to Your questions is:
    Yes, you can use the USB to TTL Device.
    No, you cant Connect it directly to the combro. You need to Connect a noninverting buffer, between the output from the combro, and the input on the TTL Interface.

    The good thing is that you have +5V available on the USB side, to Power the buffer. The simplest buffer would be 2 transistor inverters in series. I'm not sure this will work, since the output Levels from the combro is not defined, but I would have tried.
    Attached is a sketch of this.
     

    Attached Files:

  8. peter st

    peter st

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    Jan 11, 2014
    ok i get what the 10 and 100k resisters are but can you clarify for me the bits i circled thankyou peter
     

    Attached Files:

    Last edited: Jan 14, 2014
  9. peter st

    peter st

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    Jan 11, 2014
    also to build the diagram is it just a matter of soldering the resisters to each other etc and shrink wrapping or do i need to make some sort of board again thanks
     
  10. peter st

    peter st

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    Jan 11, 2014
    ok 4k7 4700 resistor :) gotta love google lol
     
  11. gorgon

    gorgon

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    Jun 6, 2011
    Circle, where?

    Depends on how resilient you want the circuit to be. I think I would have used a perf board of some kind, to give it some spine.

    Regarding the values of the components. M, k, R is multipliers for the resistance value.
    M = 1 000 000, k = 1 000, and R = 1. Always remember that M is not the same as m. m = 1/1 000.

    k is not the same as K ! K is a temperature measure, Kelvin.

    When writing decimal values with the multipliers, the letter is placed as the 'decimal' point.

    6M8, 5k6, 8R2, this reduces the fault rate, since the decimal point is easy to miss.
     
    Last edited: Jan 14, 2014
  12. peter st

    peter st

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    Jan 11, 2014
    oops my bad lol edited my thread and put pic in
     
  13. gorgon

    gorgon

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    Jun 6, 2011
    Ok, the 2 middle rings are around the two transistors. You can use mostly any NPN transistor, like the 2N2222.

    The lower ring is only around a Connection point. Both transistor's emitters are connected to 0V.

    The USB Device is connected to the right side of the sketch.
     
  14. peter st

    peter st

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    Jan 11, 2014
    thankyou very much for your help and patience
     
  15. peter st

    peter st

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    Jan 11, 2014
    ok i have 2 last questions the 2n2222's i assume i connect to the middle pin and split out via the outer pins
    and does anyone know what connector i need for the pins in this pic
     

    Attached Files:

  16. gorgon

    gorgon

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    Jun 6, 2011
  17. peter st

    peter st

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    Jan 11, 2014
    ok i asked the maker of the chrono he said it should be a Harwin 2mm but i have googled and get all sorts of results so im now more puzzled on the connector lol
     
  18. gorgon

    gorgon

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    Jun 6, 2011
    2mm is a standard pitch, so a 3pin 2mm female connector could well be the answer. If you can get a longer socket strip, you can easily cut it down to 3pin.
     
  19. peter st

    peter st

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    Jan 11, 2014
    thanks very much for your help :D still waiting on the perf boards to arrive :( but i made a mock up and it works great :cool:
    all your help has been great i would have never managed without
    Gorgon you are a great bloke :):)
     

    Attached Files:

  20. peter st

    peter st

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    Jan 11, 2014
    now i just have to make about 50 of theese lol
     
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