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  1. #91
    Join Date
    12th September 2015
    Location
    Macy IN
    Posts
    31
    Quote Originally Posted by UhClem View Post
    It is not a question of meeting my criteria but meeting the plain meaning of the NFPA requirements.

    But that would work although the alarm output looks weird. As near as I can tell it has battery + connected to both sides. PAD+ and GND would do the job.

    Or is this a side effect of trying to fit two schematics on a single page?
    Yes, it is a compound schematic. For the controller, the Alarm connector is not used.
    The alarm connector is meant for an audible buzzer that would sound, if when the Pad Disable Switch is open AND the leads are shorted AND the relay is closed, it will not provide enough current to start but will give a warning that there is a serious problem
    The Pad does not use the key switch, it uses a high current switch in series between the battery supply and the REL+. When the switch is open there is no high current voltage source to the relay also no current supplied to the coil of the relay. So if the FET fails, processor fails, or relay fails, there is no battery current supplied to PAD+. The continuity circuit will supply a small sense current as well as the current supplied by the Alarm circuit if there is a fault in the hardware.

    Last edited by kc9qzf; 2nd August 2017 at 03:23 AM.

  2. #92
    Join Date
    12th September 2015
    Location
    Macy IN
    Posts
    31

    Shield Schematics, BOM, and Software

    Attached should be a .zip file that contains schematics, BOM and software for the single pad wireless project using an Arduino Uno.


    DIY Shield.zip


    I am adding an additional .zip file which contains a program to allow you to configure the XBee when it is attached to the shield.
    Once attached and powered-up, you can upload this program and it will allow the Digi.com XCTU software to interface to the XBee.
    I am also including a sample configuration file. Please, Please, Please, if you make your own, make your own private encryption key!

    XBee for Shield.zip

    Last edited by kc9qzf; 3rd August 2017 at 09:50 PM.

  3. #93
    Join Date
    31st January 2009
    Posts
    4,298
    Quote Originally Posted by sooner.boomer View Post
    Does NAR/NFPA/etc. say *where* the safety interlock has to be? Put it at the pad, too. Only when everyone is heading away from the pad preceding the launch, does the last person at the pad (the launch DIRECTOR perhaps?) enable the interlock and allow the firing circuit to be energized. This simplifies the problem a lot.
    Beat me to it. That's exactly what I was going to suggest. That would be a safety interlock in addition to the one at the launch controller. The RX box holding it would also have an LED and/or an audible alarm indicating that an errant fire command was being received to prevent the safety interlock from being enabled. Further, each pad RX would be at least 30 feet from the pad in the direction of the LCO table, enough to prevent injury if every safety mechanism failed and the rocket was launched the moment the safety interlock was enabled.
    "I don't make jokes. I just watch the government and report the facts." - Will Rogers

    "If you don't read the newspaper, you're uninformed. If you read the newspaper, you're misinformed." - Mark Twain

  4. #94
    Join Date
    31st December 2009
    Location
    Las Cruces, NM
    Posts
    1,262
    Quote Originally Posted by Winston View Post
    Beat me to it. That's exactly what I was going to suggest. That would be a safety interlock in addition to the one at the launch controller. The RX box holding it would also have an LED and/or an audible alarm indicating that an errant fire command was being received to prevent the safety interlock from being enabled. Further, each pad RX would be at least 30 feet from the pad in the direction of the LCO table, enough to prevent injury if every safety mechanism failed and the rocket was launched the moment the safety interlock was enabled.
    This is the kind of thinking we need for safety. It includes the designed-in factors and the human factors for how the launch equipment is operated.

    The best place to include the check for launch activation is at the relay itself and with the fewest number of components (and with no software required to detect it). That is why I recommend a second pole on the relay with a simple alarm buzzer closed through that path.


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