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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/5OET25HXUIWHZXZWO6F4RQSGAN4YP4RH/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "CAJUhCTOq=Emt4hTKJKwocZjp3s2kdkX+++oCC1CVZSWmt7PzTw@mail.gmail.com", "message_id_hash": "5OET25HXUIWHZXZWO6F4RQSGAN4YP4RH", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/GOPLREH6KKWJ3FABQJRT5MZKECIDYLNV/?format=api", "sender": { "address": "normanlizeth (a) gmail.com", "mailman_id": null, "emails": null }, "sender_name": "Lizeth Norman", "subject": "[amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback Advice", "date": "2013-08-07T15:14:15Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/GOPLREH6KKWJ3FABQJRT5MZKECIDYLNV/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/YGWLJYLYTJ36ZZDVXBJPJQH6YSBWEY2Z/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Zack,\nCheck out K3NG's Arduino rotator control project. It incorporates the\nproper sensors and should, with the proper interface hardware, drive your\nhardware.\nI'm in the process of a build myself.\nNorm n3ykf\n\n\nOn Wed, Aug 7, 2013 at 9:58 AM, Zach Leffke <[email protected]> wrote:\n\n> Hello Everyone,\n>\n> I recently came into possession of a Pelco PT170-24P\n> tracking pan tilt pedestal designed to support large security cameras. My\n> intent with this new acquisition is to repurpose it as a \"low cost\" (got it\n> on Ebay for ~$75 + S&H) alternative for an antenna tracking pedestal for\n> amateur satellites. It uses 24VAC induction motors to move the azimuth and\n> elevation assemblies, pretty much just like the G5500s that I'm sure so\n> many\n> of us are familiar with. It definitely cannot support the same amount of\n> weight as the G5500, but I'm looking to construct a small, portable\n> satellite ground station node and this thing is plenty beefy enough to\n> handle a couple of Arrow style antennas. Here is the problem, it provides\n> absolutely no feedback.\n>\n>\n>\n> My question to the group is does anyone know of a non-mechanical method for\n> getting relatively accurate feedback for azimuth and elevation. I'm\n> looking\n> for an all electronic means that I can mount somewhere outside of the\n> actual\n> pedestal assembly (like perhaps on the cross-boom) that will be able to\n> provide measurement of the az/el (or pan/tilt, or yaw/pitch, whatever you\n> want to call it) position. I'm using an arduino microcontroller for the\n> tracking controller. Originally I intended to find a way to mount\n> potentiometers in inside the unit and simply use the ADCs on the arduino to\n> read the position feedback voltage from the pots, however, there is barely\n> enough space to mount an elevation feedback pot inside the unit, and there\n> is virtually no space for an azimuth feedback pot. Hence I'm looking for a\n> non-mechanical method.\n>\n>\n>\n> My first thoughts for the elevation feedback was to use the old\n> potentiometer plus nice heavy weight method mounted out on the boom. This\n> idea doesn't appeal to me very much as other factors can now affect the\n> position feedback (such as high winds). I then thought of something along\n> the lines of an accelerometer. I also tossed around the idea of a 2-axis\n> gyro for both Az/El. My issue is I have limited experience working with\n> these types of sensors, and was hoping to get advice from everyone in this\n> group. I know for example that the gyro will provide rate of motion around\n> an axis and thus I have to integrate over time to get the actual position.\n> This becomes cumbersome because now I have to keep track of time in the\n> Arduino while executing movement commands (certainly do-able, just more\n> complicated than reading an ADC voltage). Additionally, I believe these\n> devices suffer from drift and require frequent calibration (although there\n> may be a scheme of starting from a known position, say at one of the limit\n> switch contact points, for each pass that might work). I also toyed with\n> the idea of an electric compass for azimuth feedback, but I'm worried about\n> distortion of the magnetic field near the pedestal due to the AC induction\n> motors or when the antennas are radiating. In theory the motors are housed\n> inside the metal pedestal enclosure and thus are shielded from the outside\n> world, but I can just see it now, nice steady feedback when the pedestal is\n> stopped and as soon as I execute a motion command the azimuth feedback\n> starts dancing all over the place. Since the motion stop command is based\n> on achieving the target position, system instability is sure to occur.\n> Even\n> if I solve the AC motor EMI problem, I still worry that when transmitting\n> the fields could potentially be distorted if near the antenna (remember my\n> goal is a compact design) and taint the position feedback.\n>\n>\n>\n> Any ideas from the group would be greatly appreciated. I'm looking for a\n> \"sparkfun\" type solution here and if anyone has experience working with\n> accelerometers, gyros, electric compasses, etc. I would love your advice on\n> which might be the way to go for the position feedback. If you think I've\n> hit on a good idea above and should go with it please let me know. Again\n> I'm using an Arduino, so analog voltage feedback, I2C, SPI, and UART serial\n> are all on the table for communicating with the sensors to get the feedback\n> info.\n>\n>\n>\n> Thanks in advance!\n>\n>\n>\n> Sincerely,\n>\n> Zach, KJ4QLP\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", "attachments": [] }