What RS232 baud rate do you use? and why? - Page 4


View Poll Results: What RS232 baud rate do you use?

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  • 115.2 kbaud

    32 18.93%
  • 38.4 kbaud

    19 11.24%
  • 19.2 kbaud

    22 13.02%
  • 9600 baud

    65 38.46%
  • 4800 baud

    30 17.75%
  • 2400 baud and below

    8 4.73%
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Thread: What RS232 baud rate do you use? and why?

  1. #61
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    Default baud rate

    I`ve used a baud rate of 4800 E-7-1 and have had no problems uploading or downloading to the haas ,the machine is old though.
    And as far as the machine limits on x y axis, the ones we have are mechanical,we have had them changed due to the wires and conduits becoming hard and brittle due to age and have had no problems since.



  2. #62
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    Default

    070630-1650 EST USA

    GASPER:

    Why have you not tried working at higher baud rates than 4800? How long is your cable? How large are your largest files? How small the smallest?

    Old age is not the reason your cables fail, but rather the choice of insulating material by HAAS and that the insulation is probably soaked in coolant for the X-axis. PVC insulation is make flexible by the addition of plasticizers, and the coolant leaches these out of the PVC over time. In some cases in as little as 6 months with hydraulic oil.

    .



  3. #63
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    Smile higher baud rate

    I have tried higher baud rates but the machine is ancient and is far more stable at 4800,and you are right about the cables but everything deteriorates with age
    the new m/cs run at 19200 and the difference is only a few seconds on download



  4. #64
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    070731-0645 EST USA

    GASPER:

    The data transfer rate is approxoimately 500 bytes/sec @ 4800 baud, 1000 @ 9600, 2000 @ 19.2 k, 4000 @ 38.4 k, and 12,000 @ 115.2 k.

    2 seconds for a 1000 byte file, and 2000 seconds (33 minutes) for a 1 meg file at 4800 baud.
    0.1 second for 1000 bytes, and 83 seconds (1.4 minutes) for 1 meg at 115.2 kbaud.

    Obviously you are dealing with small files if you are dealing with only a few seconds difference between different baud rates.

    On your old HAAS are you using handshaking? How old is the machine? With an appropriate cable length you can get reliable data transfer (zero errors) at HAAS's maximum baud rate.

    On a 1993 HAAS with a maximum baud rate of 38.4 kbaud you should probably work reliably at that rate with up to 20 ft of Belden 8723 cable. Of course with either hardware or software handshake active. Your RS232 cable length is roughly inversely proportional to baud rate for a given type cable. There are lower capacitance cables than 8723 and these will allow a longer length at a specific baud rate.

    .



  5. #65
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    Gar,
    I agree with your basic facts and informative as always.



  6. #66
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    Default

    I am moving data at 115.2 on rs232, around 15 feet of belden shielded cable. I also dnc 8-10meg of data with no bproblem at all on a Dell workstaion to a 08 hass vf3.

    HAAS VF3-5 axis trunion
    Mastercam X3


  7. #67
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    080425-0802 EST USA

    DRD:

    What is the Belden wire number, and the capacitance per foot?

    .



  8. #68
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    Smile 115K and smiling!

    115.2K...Because I can! Thanks to Betatronics and Gordon (Shameless Plug

    RCA



  9. #69
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    Default

    The following lists baud rates and the respective maximum cable lengths:

    9600=100 feet
    38400=25 feet
    115200=6 feet

    So, if you have a 10 foot cable use 38400.

    Thanks,
    Ken Foulks


  10. #70
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    Default

    Quote Originally Posted by KenFoulks View Post
    The following lists baud rates and the respective maximum cable lengths:

    9600=100 feet
    38400=25 feet
    115200=6 feet

    So, if you have a 10 foot cable use 38400.
    Hi Ken,
    Your figures are no where near those set in the RS232 Standards. Cable length is highly dependent on the Baud Rate being used as you suggest. However, the Standard is based on a total capacitance of 2500pF, using 50 pF/foot cable, to allow maximum communication speed of 19200 to occur. If speed is reduced by a factor 2 or 4, the maximum length increases dramatically, as shown in figures obtained by test done by Texas Instruments years ago.

    Using a cable with lower capacitance allows you to span longer distances without going beyond the limitations of the standard. For example, a cable with a capacitance of 17 pF/ft will allow a maximum cable length of 147 feet (2500pF/17) at a baud rate of 19200.

    Test Results obtained by Texas Instruments using cable with a capacitance of 50 pF/foot
    Baud Rate ---- Cable Length (feet)
    19200 ---------- 50
    9600 ------------ 500
    4800 ------------ 1000
    2400 ------------ 3000

    Regards,

    Bill

    Last edited by angelw; 07-22-2012 at 01:32 AM.


  11. #71
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    Default Haas Factory Support

    Quote Originally Posted by angelw View Post
    Your figures are no where near those set in the RS232 Standards.
    Haas' recommended cable lengths are not the ideal numbers, mostly because many shops are not ideal environments for data transfer. With all of the electrical interference within a shop, combined with our inherit desire to purchase the cheapest cable possible; Haas cannot possibly recommend running at full laboratory-rated parameters.


    Quote Originally Posted by angelw View Post
    Using a cable with lower capacitance allows you to span longer distances without going beyond the limitations of the standard.
    If any Haas user would like to purchase more expensive cabling, they are likely to achieve better results. However, this is unlikely to happen very often.

    Thanks,
    Ken Foulks


  12. #72
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    Quote Originally Posted by KenFoulks View Post
    Haas' recommended cable lengths are not the ideal numbers, mostly because many shops are not ideal environments for data transfer. With all of the electrical interference within a shop, combined with our inherit desire to purchase the cheapest cable possible; Haas cannot possibly recommend running at full laboratory-rated parameters.




    If any Haas user would like to purchase more expensive cabling, they are likely to achieve better results. However, this is unlikely to happen very often.
    Hi Ken,
    The figures obtained by Texas Instruments, and indeed, the specification of cable length as defined by the Standard is not limited to lab environments, but what is achievable when “I’s” and “T’s” are respectively dotted and crossed. The cable spans indicated in my last post are indicative of what I and my colleagues achieve in any installation we do.

    The difference in price between the best and the worst cable available is infinitesimal in the whole scheme. Accordingly, I wouldn’t compromise on signal stability on the basis of the end user may use poor quality cable. I’d simply stipulate that a particular specification cable should be use, as does the RS232 Standard. If the client doesn’t comply, then it’s their problem. It’s a bit like making a cutting tool recomendation and then the client doing something else then complaining of poor tool life.

    There are things in the HAAS manual regarding RS232 communication I don't agree with.
    1. In the manual I have, it shows Protective Ground (Pin 1) of the DB25 connector at the Control End, being connected to Pin 1 of a DB9 connector at the PC end, calling the DB9 connector Pin1 Protective Ground as well. Pin 1 on a DB9 connector is in fact Data Carrier Detect (CD), with Protective Ground being the actual metal shell of the connector.

    2. Although HAAS show a connection from PG at the control end to PG at the PC end, this is potentially hazardous unless its known that the two devices are Grounded in the same place, and that both are Grounded well. If these conditions aren't satisfied a Ground Loop can result. The ground loop occurs when there is a different electrical potential between the Grounds of the two devices. This results in an electrical current being conducted through the data cable and can burn out the IC chips that send and receive the RS232 serial signals if the difference in potential is greater than about 30 volts. Accordingly, unless good grounding to the same ground can be assured for both devices, its recommended to ground the shield at the CNC end only.

    Regards,

    Bill

    Last edited by angelw; 07-24-2012 at 06:54 AM.


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What RS232 baud rate do you use? and why?

What RS232 baud rate do you use? and why?