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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/R53ORTC6VILK2HCEHBUZ3MWCMXMTYIPK/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "R53ORTC6VILK2HCEHBUZ3MWCMXMTYIPK",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/CAEWSJWJ7RLZ237M7ENOML4MWHOZCS4H/?format=api",
    "sender": {
        "address": "phelpsw (a) gmail.com",
        "mailman_id": "565989e083294de8b40d664bce45de2b",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/565989e083294de8b40d664bce45de2b/emails/?format=api"
    },
    "sender_name": "Phelps Williams",
    "subject": "[amsat-bb] Re: Dish position pulse counter",
    "date": "2008-04-25T17:13:25Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2EWA5MGMROH6M7TDA4RKI2EY462BNKPF/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Phil,\n\nHave you identified the source of the noise?  However you regulate down the\n5v for the pic, if you place a larger capacitor on the 5v regulated bus\n(between 5v and gnd) this might help with these fluctuations, essentially\nacting as a high pass filter.\n\nIf the power bus is clean, the noise might be induced along a long cable run\nto the rotor itself.  It might be worthwhile to look at a differential a2d\nwith a spi or i2c interface.\n\nTake a look at the Texas Instruments ADS1110.  It has an internal reference\nvoltage as well to help filter out these ratiometric effects.\n\nAnother option might be to switch over to a rs485 or rs422 link between the\nrotor and your shack where the controller presumably is.\n\n-Phelps\nKI6GST\n\n\nOn Fri, Apr 25, 2008 at 6:29 AM, David Barber <\[email protected]> wrote:\n\n> If pulse counting is used and since presumably the duration and expected\n> repetition of the pulse is known / can be calculated is it not possible to\n> discriminate between noise and a valid pulse?\n>\n>\n>\n> -----Original Message-----\n> From: [email protected] [mailto:[email protected]] On\n> Behalf Of i8cvs\n> Sent: 25 April 2008 11:11\n> To: Phil; AMSAT-BB\n> Subject: [amsat-bb] Re: Dish position pulse counter\n>\n> ----- Original Message -----\n> From: \"Phil\" <[email protected]>\n> To: <[email protected]>\n> Sent: Friday, April 25, 2008 1:46 AM\n> Subject: [amsat-bb] Dish position pulse counter\n>\n> > Thank you for reading this.\n> >\n> >\n> > I'm having second thoughts about the pulse counting scheme and I'm\n> > beginning to think that the tried and proven ten-turn pot method might\n> > be more fool proof.\n> > Regards,\n>\n> > Phil.\n>\n> Hi Phil\n>\n> The ten-turn pot method is also not immune from inaccuracy when the\n> voltage across the pot is close to 0 volt i.e. when the rotator is turned\n> near to 0 degrees elevation.\n> In this condition the noise voltage picked up by the cable running from\n> the\n> antenna to the control box can add with the low voltage available across\n> the\n> potentiometer.\n> Since you are able to write a program for a PIC a better method to get in\n> general a high pointing accuracy requested for a dish and expecially for a\n> big dish is to use different type of position sensors like the following:\n>\n> Sequential encoders\n> Absolute encoders\n> Selsyn or Resolvers\n>\n> With two inexpensive surplus selsyn for the azimuth and two selsyn\n> for the elevation on my dish I actually get a very accurate indication\n> of position on mechanical pointers but adding the Analog Device chip\n> AD2S80 I plan to write a program to get both precise digital indication\n> and automatic tracking with high accuracy\n>\n> Look on google for the AD2S80 data sheet and for many technical\n> applications of it with syncro-resolvers.\n>\n> Have fun\n>\n> 73\" de\n>\n> i8CVS Domenico\n>\n>\n>\n>\n>\n>\n>\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n",
    "attachments": []
}